ANEASTHETIC MANAGEMENT of TRAUMA, BURNS and ABDOMINAL SURGERY
Final Objective: This module is designed to give you a better understanding of the latest developments in managing trauma/burns, their physiological effects and the anaesthetist’s role in trauma/burns management.
Enabling Objective: To achieve this goal, you should know:
Introduction
Trauma is the leading overall cause of death in the age group from birth to 30 years. For every death, two people suffer permanent disability.
Patients suffering from multiple injuries are commonly known as major trauma victims. Best outcomes are obtained for these patients by having in place a well-developed multi-disciplinary, trauma care system.
Assume that all multiple trauma patients have a cervical spine injury, a full stomach and are hypovolaemic.
Trauma Teams Victims of major trauma are best treated by a well organised and trained team made up of staff competent in assessing and treating the spectrum of life- threatening injuries commonly seen. An experienced physician anaesthetist, possessing airway and resuscitation skills and confidence in dealing with unconscious patients, is a vital member of the team.
Whenever possible both a general surgeon and an orthopaedic surgeon should be members of the trauma team. Their presence can reduce delays in the accident department, improve the early diagnosis of life threatening injuries and lead to earlier surgery when required. Having both specialists present prevents one doctor becoming overwhelmed by complex problems in an unstable patient. The team should include a radiographer when available. Staff should wear adequate protection including gowns, gloves and eye protection. It is often possible for the team to be given prior warning of a casualty arriving, thereby allowing time for preparation. Accident & Emergency departments should have a resuscitation area set aside to receive major trauma victims with anaesthetic airway equipment and drugs, intravenous fluids with blood giving sets and blood warmers. Surgical sets should include equipment for the following procedures: urinary catheterisation (including suprapubic), peritoneal lavage, pleural drainage (chest drains sets with underwater seal) and needle and surgical cricothyrotomy. Specific provision should be made for children with appropriate sizes of equipment to deal with all ages and equipment for intraosseous fluid.
Methods of Managing Trauma
A multidisciplinary approach is required in the management of major trauma and the same technique for assessment and treatment of each patient should be followed. Most modern trauma systems have a fairly rigid protocol to follow, thus reducing the opportunity for misdiagnosis.
The most widely taught system is the Advanced Trauma Life Support (ATLS) Program for Physicians, devised and disseminated by the American College of Surgeons.
Timing of death resulting from trauma
The mortality due to injury occurs during one of the following time periods:
The first peak of death occurs at the time of the injury. It may be instantaneous or within the first few minutes and is due to an overwhelming primary injury to major organs or structures such as brain, heart or great vessels. In most situations these injuries are irrecoverable, although rapid treatment and transfer may salvage some patients. Primary prevention (e.g. seatbelts) has a major role in reducing the incidence of these deaths.
The second peak lasts from the end of this first period to several hours after the injury has occurred. It is during this time that many causes of morbidity and mortality are preventable by avoidance of a secondary injury due to hypoxia, haemorrhage or any process that leads to inadequate tissue perfusion. Reversible conditions may include intracranial haematomas, major haemorrhage from viscera, bones and vessels or pneumothoraces. Even with moderate facilities many lives can be saved by simple measures.
The third peak of death occurs days or weeks after the injury from sepsis and multiple organ failure. Advances in intensive care treatment may reduce deaths but improvements in the initial management on admission will also reduce morbidity and mortality.
Initial evaluation of the trauma patient
The patient suffering multiple traumas must be thoroughly assessed on admission so that life-threatening injuries can be immediately identified and corrected. The condition of the patient must be stabilised and plans made for further treatment of their injuries. The team leader is responsible for assessing the patient and coordinating the work of the other members of the team, whose role is to treat the injuries as directed by the leader.
All trauma cases should receive:
Primary Survey and Resuscitation
The purpose of the primary survey is to diagnose immediate life threatening conditions. These must be treated as soon as they are discovered before continuing the survey. The survey is planned as follows:
Airway control with cervical spine protection.
Breathing.
Circulation and control of haemorrhage.
Disorders of the central nervous system.
Exposure of the whole body.
During the course of the primary survey, any deterioration in the patient’s condition must be managed by reassessing the patient from the start of the survey.
Airway control and cervical spine protection.
Always ensure that the patient has an unobstructed airway. If the patient can answer questions appropriately, then it is unlikely that there is any immediate threat to the airway. Noisy or laboured respiration or paradoxical respiratory movements (when the movements of the chest and abdomen are not in phase) are evidence of airway obstruction. Vomit, blood or foreign material in the mouth must be removed manually or with a sucker. Sometimes a simple chin lift and or jaw thrust is all that is required to prevent the tongue of an unconscious patient obstructing the airway, however often patients require advanced airway techniques. An oropharyngeal/nasopharyngeal airway may be beneficial but must be the correct size and inserted carefully.
Any patient with a possible cervical spine injury (unconscious, mechanism of trauma, neck pain or neurological deficit) must have their neck immobilised in a neutral position to prevent secondary spinal damage. Cervical spine damage is likely with deceleration injury, hyperflexion or extension injury or any blunt injury above the clavicles. A fracture of the first rib seen on chest X-ray indicates high-energy transfer and should always raise suspicion of cervical injury as well as intrathoracic damage. When available a closely fitting hard cervical collar should be applied with sand bags placed on either side of the head and the patient immobilised on a spine board. Soft collars are ineffective for immobilising the neck.
Intravenous anaesthesia/muscle relaxation (rapid sequence induction) should only be used by an experienced anaesthetist when successful intubation of the trachea with inline stabilisation of the cervical spine can be guaranteed. If sever facial disruption or anatomical disorders make intubation unlikely, then a cricothyrotomy should be performed.
Breathing.
The patient must be assessed for tracheal deviation or unequal chest expansion. Pulse oximetry is a valuable monitor of adequate perfusion and arterial oxygen saturation. High concentration oxygen should be administered to every patient.
The following life threatening respiratory conditions need immediate treatment:
Tension pneumothorax
Massive haemothorax
Flail chest
Open chest wound
Disruption of the tracheobronchial tree.
A tension pneumothorax is suggested by a rapid respiratory rate, mediastinal (tracheal) shift away from the affected side, and hyper-resonance and reduced breath sounds on the affected side. It should be treated initially by needle decompression of the pleural cavity at the second intercostal space in the mid clavicular line, followed by formal pleural drainage with an intercostal catheter/underwater seal drain. It is important to remember that a simple pneumothorax may be changed into a tension pneumothorax with positive pressure ventilation. A chest drain should be inserted prophylactically before positive pressure ventilation.
A massive haemothorax is suggested by reduced breath sounds, dullness to percussion and a shift of the mediastinum away from the affected of the above side often accompanied by cardiovascular instability. It should be treated with formal pleural drainage and if the initial volume of blood exceeds 1500 ml or bleeding continues at a rate greater than 200 ml/h, a thoracotomy is indicated.
The anaesthetist must be aware that endobronchial intubation can mimic both. The endotracheal tube position must be checked before making a diagnosis of pneumothorax or haemothorax.
Flail chest means that part of the chest wall is able to move independently to the remainder of the chest and occurs when ribs are fractured in at least two places. The flail segment falls during inspiration while the rest of the chest rises. It is always associated with significant pulmonary contusion and hypoxia. If respiratory failure develops despite oxygen therapy and adequate analgesia (preferably epidural or intercostal blocks), the intubation and positive pressure ventilation is required.
An open chest wound needs covering and sealing on three sides immediately. The flapping motion of the free edge of the dressing forms a one-way valve , which prevents air being sucked into the pleural cavity from outside.
This should be followed by formal pleural drainage and possibly thoracotomy. Once the pleural cavity is drained, the wound may be closed.
Patients with a major disruption of the tracheobronchial tree need immediate endotracheal or endobronchial intubation and thoracotomy. The condition is most often diagnosed by the presence of pneumomediastinum, pneumopericardium or surgical emphysema. Minor tears may sometimes be treated conservatively.
Circulation.
The circulation is initially assessed by palpating the pulses, assessing skin colour and capillary refill, conscious state and by measuring the blood pressure. Intravenous access should be obtained with at least two large bore cannulae. Blood should be taken at the time of cannulation and crossmatch blood ordered as a priority.
Any major haemorrhage that is visible should be controlled by direct pressure. Tourniquets should not be used. Penetrating objects should be left for formal surgical exploration.
The most common cause of shock in multiply injured patients is haemorrhage. Blood loss from a fractured humerus may be up to 800ml, from a fractured femur 200ml and from a fractured pelvis 3000ml. Intra-cranial haemorrhage is insufficient to cause shock in an adult.
Hypovolaemia is often categorised into 4 classes.
Class of hypovolaemia
Class
I
Class
II
Class
III
Class
IV
Blood Loss:
% Circulating volume
<15
15-30
30-40
>40
Blood Loss:
Volume (mls in adults)
<750
750-1500
1500-2000
>2000
Pulse
Normal
100-120 bpm
120 bpm Weak
>120 bpm Very weak
Blood Pressure:
Systolic
Normal
Normal
Low
Very Low
Blood Pressure:
Diastolic
Normal
High
Low
Very Low
Capillary Refill
Normal
Slow
Slow
Absent
Mental State
Alert
Anxious
Confused
Lethargic
Respiratory Rate
Normal
Normal
Tachypnoeic
Tachypnoeic
Urine Output
>30 mls/hr
20-30 mls/hr
5-20 mls/hr
<5 mls/hr
It must be stressed that there is variation from this guide, particularly in the elderly, in those with previous medical conditions or those who are taking cardiovascular medications who all tolerate hypovolaemia poorly. It must be remembered that anaesthesia will obtund the compensatory sympathetic response to hypovalaemia and may cause cardiovascular collapse.
Volume resuscitation begins immediately with the establishment of venous access. Most trauma patients are hypovolaemic and the restoration of the circulating volume is always the first priority of fluid management. The second priority is the restoration of blood carrying capacity followed by the normalisation of coagulation status.
The amount and type of fluid administered will depend on the type and extent of injury. Usually 10-20 ml/kg of colloid or 20-30 ml/kg of crystalloid is administered as an initial bolus and the patient is reassessed and boluses continued until the patient is clinically resuscitated. Whenever possible the fluid should be warmed to prevent further cooling of the patient.
Hypotension may also result from cardiac failure which is, however, rare in trauma patients and is likely to be due to cardiac injury, either myocardial contusion (which should be expected in blunt thoracic trauma), or cardiac tamponade (which should be suspected in penetrating chest injury when shocked patients do not respond to fluid resuscitation and the degree of hypotension is greater than the apparent blood loss). Cardiac tamponade will cause a raised jugular venous pressure, muffled heart, hypotension, tachycardia and pulsus paradoxus. Cardiac tamponade needs emergency treatment by needle pericardiocentesis followed by formal surgical exploration and repair.
Disorders of the central nervous system.
The central nervous system should be quickly assessed by checking the patient’s level of consciousness, spinal cord function and pupillary response to light. Conscious level is assess by recording the patient’s eye opening and motor response to graded stimuli (spontaneous, in response to direct questioning, pain or no response). All four limbs should be tested to assess the spinal cord function.
Exposure.
All patients with multiple injuries should be completely undressed to allow a thorough survey of injuries. Clothes may be cut off if necessary to minimise undesirable patient movement. However, the patient must not be allowed to become hypothermic and should be kept covered when possible and the resuscitation room should be warm. Injured children lose heat rapidly when exposed.
During the course of the primary survey, the five most important rules to remember are:
Airway breathing circulation
The patient should be repeatedly reassessed, particularly if clinical signs change.
Any immediately life-threatening condition should be treated without delay.
Penetrating wounds and foreign bodies must be left for formal surgical exploration.
Any external bleeding should be stopped by using direct pressure.
Secondary Survey
Following the initial survey and resuscitation, the patient should undergo a thorough secondary survey with the aim of documenting any other injuries. During this survey the basics of the primary survey (airway, breathing and circulation) must be regularly reassessed. Tetanus immunisation and prophylactic antibiotics can be administered if necessary. A history should be obtained and X-rays of the lateral cervical spine, chest and pelvis taken. (Remember however that lateral cervical spine X-rays may fail to reveal up to 20% of cervical spine injuries).
History.
A full history is required, particularly allergies, medications and tetanus immunity, previous medical history, fasting status and the events leading to the injury.
Vital information can be gained from the history or the events leading to the injury and particular attention should be paid to the mechanism of injury. The extent and severity of injury is related to the amount of energy transferred to the patient. In blunt trauma, commonly associated with road traffic accidents and falls, there are a number of situations, which are associated with life-threatening injuries:
“Top to toe”
Head. The Glasgow Coma Scale score should be assessed. The scalp should be palpated for fractures, lacerations and other deformities. Adults rarely lose a significant amount of blood from scalp wounds but bleeding should be stopped. Any injury to or around the eye should be noted. Periorbital and/or subconjunctival haemorrhage may indicate a base of skull fracture. Blood or cerebrospinal fluid coming from the ears or nose may also indicate a base of skull fracture.
Facial fractures must be sought by careful palpation, but only treated at this stage if likely to compromise airway patency. Swelling or haemorrhage associated with such fractures may cause delayed respiratory obstruction and must be anticipated. Movement of the maxilla indicates a middle third fracture.
Neck. The patient should be asked if they have any neck pain. With an assistant performing in-line immobilisation, the tapes, sand bags and neck collar should be gently removed and the neck examined for lacerations, swellings, tenderness or deformity of the cervical spine. Penetrating neck wounds must be explored under general anaesthesia.
The cervical spine should have lateral, antero-posterior and odontoid peg views. A lateral X-ray of the cervical spine must show all the vertebrae including the body of the first thoracic vertebra. X-rays alone cannot detect all injuries to the cervical spine and much depends on the history and examination.
Chest. The entire chest must be examined for signs of injury. This includes palpating for fractures of the clavicles and ribs and the presence of subcutaneous emphysema. Percutaneous drainage of haemo/pneumothoraces must be performed when they are diagnosed or strongly suspected. Deceleration injuries may cause tracheobronchial injury, transection of the thoracic aorta, cardiac injury and diaphragmatic rupture.
Complete aortic transection is immediately fatal. Incomplete aortic transection is suggested by the history, chest X-ray signs of widening of the mediastinum, pleural capping (fluid shadow at the apex of the lung) and a shift of the trachea to the right and/or inferior displacement of the left main bronchus.
Cardiac contusion may be suggested by the history, inadequate response to intravenous fluids, high central venous pressure and ECG changes. Investigations include echocardiography, which may show abnormal heart wall movement and/or a pericardial effusion. Echocardiaography is also useful in diagnosing heart valve rupture.
Diaphragmatic rupture is commoner on the left side and is diagnosed by history, dyspnoea and abdominal contents visible on chest X-ray within the thoracic cavity. A right-sided diaphragmatic hernia is more difficult to diagnose. If a diaphragmatic hernia is suspected, a radio-opaque nasogastric tube should be inserted and the chest X-ray repeated. Surgical repair is required.
Abdomen. The abdomen must be inspected for signs of injury and the presence of free intraperitoneal fluid. Ultrasound can allow rapid assessment of many intraabdominal injuries. Penetrating wounds should be examined at laparotomy if they breach the muscle. Eviscerated bowel must be covered with packs soaked in warm saline. The pelvis must always be X-rayed. Blood at the urethral meatus or scrotal haematoma indicates urethral injury in the male. In this situation a supra-pubic catheter should be inserted. Otherwise a urethral catheter should be inserted, and the presence of any obvious or microscopic haematuria sought. A rectal examination may also reveal blood or pelvic fractures, and an assessment of anal tone can be made. A lax anal sphincter may indicate that spinal cord injury has occurred. The stomach may dilate acutely in trauma patients, and may need decompression using a nasogastric tube (or an oro-gastric tube if a base of skull or mid face fracture is suspected). Vaginal examination may show a pelvic fracture or breach of the vaginal vault.
If assessment is difficult or equivocal, then diagnostic peritoneal lavage is indicated. It should not be performed if there is a need for urgent laparotomy i.e. penetrating trauma, unexplained hypovolaemia, extruded bowel or radiological evidence of intra-abdominal trauma.
Limbs. Fractures, wounds and discolouration must be noted. Check pulses in all limbs even if no fracture is suspected. Fractures compromising circulation must be rapidly reduced to prevent distal ischaemia. Fractures should be splinted to reduce pain and the risk of fat emboli.
Foreign material and devitalised tissue should be removed. Large blood losses may be associated with long bone and particularly pelvic fractures, but in a shocked patient they must not be assumed to be the only cause. Early fixation of these fractures may reduce blood loss, accelerate mobilisation and reduce the severity of fat embolism. Signs such as increased swelling, pain and altered sensation suggest that the patient may have developed a compartment syndrome, which requires urgent fasciotomy.
Spine. Hypotension with bradycardia is unusual in hypovolaemia but if present does not exclude haemorrhage, especially in the elderly. It is however, more likely to be due to spinal cord damage in a patient with a history suggestive of spinal cord injury. Fluid replacement should be guided by careful monitoring to avoid over fluid resuscitation. Other indicators of cord damage are acute urinary retention, diaphragmatic respiration, priapism lax anal sphincter and flaccid paralysis of the limbs.
The cervical and thoracolumbar regions are most commonly affected by trauma and appropriate X rays must be taken. The patient must be log rolled and the entire back examined.
The further treatment will depend on the injuries detected, with priority given to those which are most severe/life threatening.
Transport. The transfer of the patient with multiple traumas can be hazardous. In all but the most desperate situations, the condition of the patient should be stabilised prior to transfer. The level of monitoring must be maintained during transport, adequate resuscitation equipment and drugs should be available, hypothermia avoided and the receiving carers must be warned of the condition of the patient. The staff that accompanies the patient must be experienced in the care of critically ill patients.
Anaesthesia for Trauma.
As with anaesthesia for all patients, the key to successful trauma anaesthesia is the adequate assessment and pre-operative resuscitation of the patient. In all but the most urgent surgery, there is sufficient time for this to occur.
The safe fasting time prior to anaesthesia after trauma is uncertain. In the patient undergoing immediate or early surgery (< 12 hours) operation the most important time interval is that between their last meal and the injury, as after the injury gastric emptying may cease. In those having surgery after a period of stabilisation and observation on the ward, the patient is often assumed to have an empty stomach if they are not in severe pain or have no other reasons to delay gastric emptying.
Preoperative assessment. All injuries must be found. If the patient has been admitted using the trauma assessment method above, then it is unlikely that serious injuries will be missed. If the patient has not had a trauma assessment, the anaesthetist must thoroughly examine he patient from head to toe. In addition a specific anaesthetic assessment should be performed. The appropriate investigations will depend on the injuries sustained and the operation planned. A blood crossmatch must be performed. Premedication is usually not necessary if the patient is kept pain free. Pre-operative antibiotics and tetanus vaccination are usually required.
A variety of methods of pain relief are available including nerve blocks (e.g. femoral nerve block), opioids paracetamol, non-steroidal anti-inflammatory drugs and inhaled analgesics (e.g. methoxyflurane and nitrous oxide). Opioids are best administered intravenously or by sub-cutaneous injection in small increments until acceptable analgesia is obtained. Nitrous oxide is best avoided in patients with chest trauma who may have a pnuemothorax or in scuba diving accidents.
Those patients with a thoracic injury should be investigated for the presence of fractured ribs as well as haemo- or pneumothoraces. If positive pressure ventilation is to be used, then they will require an intrapleural underwater seal drain to prevent the development of a tension pneumothorax during anaesthesia. Possible cardiac contusion must not be overlooked. It may present as persistent hypotension despite aggressive fluid replacement. A 12 lead ECG recording may assist in the diagnosis.
Hypovolaemia must be corrected before general or regional (spinal/epidural) anaesthesia. All anaesthesia may reduce the sympathetic nervous system activity, which is preventing hypotension in the hypovolaemic patient, causing a sudden and large drop in blood pressure. Patients should ideally be normotensive without a tachycardia before proceeding with anaesthesia. Even ketamine which usually does not cause a fall in blood pressure may do so is severely injured patients.
Care must be taken not to move a suspected cervical spine injury during transfer, positioning and airway manoeuvres (in-line stabilisation). Depolarising neuromuscular blocking agents (suxamethonium) may cause a life threatening rise in serum potassium in patients with burns, spinal cord damage or severe muscle atrophy and can only be safely used in the first 24 hours after the injury. Patients with head injury will require careful consideration of blood pressure and intracranial pressure control. Ketamine raises ICP.
Surgery for major trauma may be long with significant blood loss. The anaesthetist must continue to monitor blood loss and must administer appropriate fluids (crystalloid, colloid, blood, blood products) to prevent hypovolaemia, anaemia and coagulopathy. Appropriate fluid management can be helped by frequent laboratory investigations. The patient is also at risk of hypothermia.
In addition the patient must be observed carefully for any changes in vital signs which are unexpected and which might be the result of an undiagnosed injury (for example hypotension caused by undiagnosed intra-abdominal injury during an operation to repair a fractured femur). Good communication between the surgeon and anaesthetist is essential.
Unexplained hypoxia in the perioperative period where there is a long bone or pelvic fracture may be due to fat embolism associated with the release of intramedullary fat into the venous circulation from the fracture site. This can occur at any time following fracture, but is more common if surgical fixation is delayed for longer than 8 hours. The lung injury is characterised by capillary leak leading to pulmonary oedema (this occurs in the absence of heart failure). Hypoxia is always present and respiratory failure is common. The lung injury can be associated with systemic capillary injury commonly affecting the cerebral circulation, leading to confusion and decreased conscious state. A petechial rash is usually present over the trunk and conjunctiva. Renal impairment can occur. Treatment of fat embolism involves respiratory support with oxygen therapy and ventilation, and circulatory and renal support if required.
The key to successful trauma management involves prior preparation of the resuscitation room and creation of a trauma team in which the anaesthetist plays a vial role. The trauma team should be co-ordinated by a leader who should follow a primary survey and resuscitation, a secondary survey once the patient has been stabilised and prompt initiation of definitive treatment. A full history should identify mechanisms of injury. Anaesthesia for the trauma patient must involve a full assessment of the actual and potential injuries with the appreciation that resuscitation is often ongoing and that the patient’s condition can change dramatically.
The Burn Injury.
Burn injury can result from many causes; the majority of cases are due to thermal, chemical and electrical injuries. The commonest cause of death is by smoke inhalation.
Deep thermal injury destroys skin, the body’s barrier to the external environment. Skin plays a vital role in thermal regulation, fluid and electrolyte homeostasis, and protection against bacterial infection. Significant heat loss, massive fluid shifts and protein losses, and infections commonly occur in patients with severe thermal injuries. There is also a diffuse alteration in the permeability of cell membranes to sodium, resulting in generalised cellular swelling. Microvascular injury results from local damage by heat and from the release of vasoactive substances from the burned tissue. Therefore oedema occurs in both burned and unburned tissues.
In electrical burns current passage creates thermal energy that actually destroys tissue, particularly tissues with high resistance such as skin and bone. The course of the electrical current is often occult. The precise location and extent of tissue damage may not be revealed by physical examination.
In chemical burns the degree of injury depends on the particular chemical, its concentration, duration of contact, and the penetrability and resistance of the tissues involved. Some substances producing chemical burns, such as phosphorus, are absorbed systemically, producing significant and often life-threatening injury.
Infections and drug reactions may also cause extensive and life-threatening dermal injury.
ASSESSMENT
Burns are a form of trauma; thus the airway, breathing and circulation (ABCs) should be initially assessed. ‘ABCs’, gaining IV access, starting fluid resuscitation and providing pain relief are the cornerstones of the initial management. Potential airway compromise will be suggested by the history, facial burns, soot staining around the nostrils, singed nasal hairs etc.
The size of the burn should be estimated as a percentage of the total body surface area (%TBSA) and is an important guide to the severity of the burn. The ‘Rule of Nines’ guides estimations in patients over 14yrs of age:
Adults. The head and both of the upper extremities represent 9% TBSA each. The anterior trunk, posterior trunk, and both lower extremities represent 18% TBSA each.
Infants and children. Because of the different proportions of body surface area relative to patient age, reference must be made to the proper burn chart when calculating %TBSA to avoid significant errors. Another practical method to estimate %TBSA is that the area of the patient’s hand covers about 1% TBSA.
The depth of the burn is important for the planning of therapy (i.e. conservative management vs. excision and grafting). Erythema is not included in the estimate of the burned area. Nevertheless these areas, rather like sunburn, may be painful but will not be blistered and will heal normally without treatment. Superficial partial-thickness, deep partial-thickness and full thickness areas are included in the estimated area. The distinction between superficial and deep is of importance as the former has a better prospect of healing without scarring. Under resuscitation can cause deterioration of burned areas to a more severe grade.
Burn depth is difficult to determine visually; however there are some useful guidelines. The area under a partial-thickness burn usually has normal or increased sensitivity to pain and temperature and blanches with pressure. A full-thickness burn is anaesthetic and does not blanch.
Complex burns include destruction of tissues deep to the skin such as tendon, muscle and bone. Burns to the face, airway and perineum would also be included as complex burns.
Fluid loss. During the first 24 to 28 hours, massive evaporative losses and sequestration of fluid in the extracellular compartment (third spacing) are to be expected. Aggressive fluid repletion is necessary to prevent hypotension, hypo-perfusion, and shock. The composition of lost or sequestered fluid is very similar to that of plasma (i.e. the fluid has a high protein content).
Burns less than 10% TBSA do not normally require formal resuscitation, although admission for assessment, pain relief and investigation of circumstances may be required. Concurrent medical illness may make oxygen and fluids necessary even for <10%, for example in children with renal disease or with complex burns.
Burns greater than 10% and less than 30% may be classified as moderate in severity and will require oxygen, fluid resuscitation, pain relief and naso-gastric feeding. As severity approaches 30% TBSA, a systemic inflammatory response of pyrexia, raised white count and raised CRP in the absence of infection becomes more likely but only if the burn remains un-excised and only after 24-48 hours. For less severe burns, close to the time of injury, pyrexia and raised indices of infection may indicate true infection. Cultures should be taken and the wound inspected prior to starting antibiotic therapy. If pre-existing skin disease is present infection may occur early
Concomitant smoke inhalation and cutaneous burns between 10 and 30% indicates at least HDU based management.
Burns >30% TBSA represents a major injury where a systemic response is universal. Mortality is high if management is not optimal, even in young patients. The management of these more major burns involves Oxygen, fluids, feeding & pain relief as before, but with the need for invasive monitoring to guide therapy and for ventilation in a higher proportion of cases. Prophylactic antibiotics are not usually given except as part of a 'Selective Decontamination of the Digestive Tract', regimen in the more severe burns expected to be ventilated long term (in some units).
RESUSCITATION.
Aims to:
Thermal injury of the face and upper airway is a common occurrence, but burns involving the lower respiratory tract are infrequent. However, during a fire within a closed space or when heated noxious vapours are inhaled, inhalation injury may occur. This should be suspected in the presence of burns of the head or neck; singed nasal hairs; swelling of the mucosa of the nose, mouth, lips or throat; a brassy cough; or carbonaceous sputum. Both the upper airway and pulmonary parenchyma may be severely affected. Before airway oedema occurs, endotracheal intubation should be performed expeditiously. Continued swelling and distortion of the soft tissues progresses at a rapid rate, rendering intubation difficult, if not impossible.
The inhalation of toxic fumesmay directly damage the tracheobronchial tree and produce additional systemic effects. Combustion of polyurethane-containing products(e.g. insulation and wall panelling) releases hydrogen cyanide, a cell poison - leads to tissue hypoxia and death. The ambient oxygen concentration is reduced and the carbon monoxideconcentration is increased during a fire. Carbon monoxide poisoningoccurs when carbon monoxide combines with haemoglobin, displacing oxygen (carbon monoxide is bound more than 200 times as firmly as oxygen) and shifting the oxyhaemoglobin dissociation curve to the left. Tissue hypoxia ensues. Carbon monoxide toxicity may be difficult to diagnose because carboxyhaemoglobin appears similar to oxyhaemoglobin, and partial oxygen pressure (Pa02) measurements are in the normal range (unless there is underlying pulmonary parenchymal injury). Conventional pulse oximetry is unable to differentiate between oxyhaemoglobin and carboxyhaemoglobin.
Diagnosis is made by the direct measurement of carboxyhaemoglobin levels. The half-life of carboxyhaemoglobin is directly related to the inspired oxygen concentration (FiO2); it is 5 to 6 hours when breathing room air, but 30 to 60 minutes while breathing 100% oxygen. Hyperbaric oxygen at 3 atmospheres further reduces carboxyhaemoglobin half-life to 20 to 30 minutes. Thus treatment consists of supplemental oxygen (hyperbaric oxygen in severe cases) and supportive care until the carbon monoxide is eliminated. All burned patients, especially those burned while within a closed space, may have sustained some degree of tissue hypoxia with the thermal injury. Oxygen administration should begin at the scene. The inhalation of particulate matter(i.e. smoke and soot) results in mechanical obstruction of the airways.
Fluid Regimens
These are guides for appropriate replacement. All 'recipes', require monitoring and adjustment. The commonest now used is the Parkland formula. This is calculated having an accurate assessment of the burned area and the body weight, suggesting a volume of Ringer-Lactate (Hartmann’s Solution) given by:
2-4 mls per %TBSA per Kg body weight
This volume is given over the 24 hours following injury, half the (volume) being given over the first 8 hours from the injury. For example a 70 Kg Man with a 50% BSA Superficial partial thickness injury would require 7-14 (4x50x70/1000) litres over the first 24 hours. Experience suggests that those patients with smoke inhalation injury need still more fluids, as do those with extensive partial thickness burns.
If it has taken several hours for the patient to reach medical attention the first half may need to be given at a 'front loaded', accelerated rate for a couple of hours in order to catch up. It is important that under-resuscitation is avoided. The fluid should be warmed to ensure that the development of hypothermia doesn't complicate clotting function or cause inappropriate vasoconstriction.
Oliguria, haemoconcentration and hypotension are all signs of inadequate fluid administration under these circumstances.
Adequate cerebral function, brisk capillary refill, appropriate blood pressure and urine output in the range 0.5-1.0ml/kg/h output (1.0-2.0ml/kg/h urine output in children) suggest adequate resuscitation.
In larger burns and in patients with pre-existing impaired physiology, invasive monitoring with CVP or pulmonary artery flotation catheters may gauge adequacy of fluid replacement more effectively. These are best used early and removed before greater morbidity occurs due to infection.
Big burns themselves appear to have cardio-depressant effects. A decrease of cardiac output and arterial blood pressuremay occur in the immediate post burn period, despite adequate volume resuscitation. The cause of this phenomenon remains unclear but may be related to circulating factors that depress myocardial contractility.
Capillary integrityis re-established 36 to 72 hours after the initial injury, allowing resorption of fluid from the interstitial space and decreasing the need for fluid infusion. At this time, a “diuretic phase” may begin.
A hypermetabolic statedevelops 3 to 5 days following the burn injury. This may result in a two-to-threefold increase in cardiac output, which persists for weeks to months. However, Gram-negative sepsis may cause continued depression of cardiac output in some patients. Chronic post burn hypertensionmay be seen in young children (usually boys) who have sustained extensive burns. The syndrome usually develops within 2 weeks of injury and may result from elevated endogenous catecholamine levels.
Circumferential burns of the abdomenmay produce increased intra-abdominal pressure, which can reduce cardiac output by decreasing venous return.
Circumferential full-thickness burns of the thorax decrease chest wall compliance, which can lead to hypoxaemia and respiratory failure. Emergency escharotomies are frequently required.
If myoglobinuria is seen it is appropriate to aim for higher levels of urine output driven by osmotic diuresis with Mannitol. Up to 12.5 grams of Mannitol can be given per litre of resuscitation fluid (ATLS). This can give a sense of false security as urine output may be maintained while the patient remains dry overall. The overall fluid balance requires more careful monitoring under these circumstances.
Maintenance fluids appropriate to the age and weight of the patient are also required. In small children the use of Dextrose 4%/Saline 0.18% solutions will exaggerate the hyponatraemia. This will increase the likelihood of seizures. In any significant burn injury the use of the enteral route for administration of maintenance fluid as feed will reduce the tendency to low sodium and will minimise the loss of muscle to the catabolic response over the full duration of the injury.
The continuation of the Parkland formula involves a further 24 hours of fluid resuscitation again based upon Hartmann’s solution with 2ml/%TBSA/kg plus 0.5ml/%TBSA/kg of colloid.
ANAESTHETIC CONSIDERATIONS.
Initial care requires attention to detail in terms of pre-operative assessment of the patient. Both the history and events following the injury and the patients' personal history are important. The priorities are to maintain safety for the individual undergoing treatment, while maintaining an eye to the future, protecting vascular access and making appropriate airway care decisions.
The interaction of anaesthetic agents with the patient's physiology changes over time. At initial presentation for early excision and grafting, the anaesthetist may be faced with a patient who is undergoing resuscitation but remains hypovolaemic; their airway may be compromised by the oedema of both burn and crystalloid resuscitation (or is becoming so); their vascular access may be compromised by the burn itself and there may be significant problems with the acute pain of the injury. During the chronic phase of burns management, when reconstructive procedures are performed – altered pharmacokinetics, drug tolerance and extremely difficult airways are the main considerations.
Monitoring and IV access: Often IV access is still in place from the initial resuscitation. Large bore IV lies are mandatory to allow for massive fluid replacement. The cannulation site depends on the availability of unburned areas. If all appropriate sites are burned, the line may have to be placed through the burn wound after the area has been prepared in a sterile fashion. In massive burns, ECG electrodes may have to be placed directly on debrided tissue. Central venous pressure linesare useful, both for monitoring central volume and as central access for drug infusions.
Airway: Obtaining an adequate mask fit may be difficult because of oedema in the early phases of burn injury or because of scars and contractures later on. These same processes can render the trachea in burn patients extremely difficult to intubate.
Muscle relaxants: Succinylcholine is absolutely contraindicated 24 hours to 2 years after major burns, since it can produce profound hyperkalaemia and cardiac arrest.
This can develop as cholinergic sensitive ion channels migrate and increase in muscle beyond the motor end plate. Similar considerations apply to any ICU patient who is denervated, immobilised, or has had repeated sepsis. Suxamethonium can be used for rapid sequence induction early on provided it is thought essential. The same proliferation of binding sites with changes in metabolism, increase the requirement for non-depolarising agents for a given duration of effect for many months after injury.
Non-depolarising relaxantsare used when muscle relaxation is required. Burn patients show a “resistance” to these drugs (diminished response to conventional doses), in some cases requiring three-to-fivefold higher doses than non-burned patients.
Analgesics: There is no single preferred agent or combination of agents. These patients may have greatly increased narcotic requirementsbecause of tolerance and increases in the apparent volume of distribution for drugs. It is important to provide adequate analgesia. Ketamine is very useful for pain management and anaesthesia.
Temperature regulation. The most comfortable body temperature for a burn patient is about 38°C. In the burn unit patients are cared for in warmed, humidified environment. Every effort should be made to maintain normothermia during transport and surgery. The operating room, IV fluids, and blood products should be warmed, and inspired gases heated and humidified. Paediatric patients should be placed under a radiant heat source and on a warming blanket whenever possible.
Immunosuppression. The immune system is suppressed for weeks to months after burn injury, and the wound itself serves as an excellent medium for bacterial growth. Every attempt should be made to practice aseptic technique when handling patients, suctioning airways or inserting intravascular lines.
Postanaesthetic care. It is important to maintain normothermia while transporting patients back to the burns unit, since shivering could contribute to graft loss. Supplemental oxygen should be given until patients are fully recovered from anaesthesia.
Abdominal Surgery.
Anaesthesia for Abdominal Surgery
Preoperative Assessment and Optimisation For the patient requiring emergency abdominal surgery, with few exceptions, there is time to assess properly, and to resuscitate, before induction of anaesthesia. A systematic approach is best - it avoids overlooking important matters. There are some situations where the patient must go to theatre immediately - they include severe foetal distress, uncontrollable internal haemorrhage. In these situations, history, examination, resuscitation have to be done “on the run” and with no delay. In most other situations, a short delay for resuscitation is best for the patient.
Assessment must also include a thorough review of coexisting organ dysfunction. Common coexisting disorders include renal impairment, diabetes, ischaemic heart disease and chronic obstructive airways disease. Intra-abdominal pathology can contribute to respiratory insufficiency by decreasing functional residual capacity and can potentiate reflux of gastric contents.
Assessment of preoperative fluid status is of critical importance; is of fundamental importance; surgical diseases and conditions may cause severe changes in volume status producing both hypovolemia and anaemia.
History of fluid losses
· Bleeding: gastrointestinal tract sources include ulcers, neoplasms, oesophageal varices, diverticuli, angiodysplasia, or haemorrhoids.
· Emesis or gastric drainage may lead to significant losses, particularly in patients with bowel obstruction. Quantity, quality (presence of blood), and frequency of emesis should be assessed.
· Diarrhoea from intestinal disease, infection, or cathartic bowel preparation may lead to 1 to 2 litres of extra cellular fluid loss in the immediate preoperative period.
· Sequestration of fluid either in bowel lumen from ileus or interstitium from peritonitis.
· Fever increases insensible fluid loss.
Physical signs of hypovolemia
Postural changes in vital signs (increased heart rate and decreased blood pressure) may reveal mild to moderate hypovolemia; severe hypovolemia produces tachycardia and hypotension. Dry mucous membranes, skin mottling, and decreased skin turgor and temperature indicate decreased peripheral perfusion resulting from hypovolemia.
Investigations
Investigations may be clinical or laboratory. Clinical investigations are part of physical examination, and include the “bedside forced expiratory volume”, measured with a spirometer or by listening to rapid exhalation. Laboratory analysis including haematocrit, serum osmolality, urea-creatinine ratio and electrolytes may be helpful in estimating volume deficits. Laboratory investigations should always be requested if they would help to identify a problem, which can be corrected. Once ordered, they must be checked and acted upon. Once again, they may or may not influence a clinical decision to delay the operation, or to proceed.
Of the more commonly available investigations, Haemoglobin value must be interpreted in the context of the usual Hb of the population (which may be 8-9gm/dl in some areas, 12-13gm/dl in others) as well as in the context of bleeding or dehydration. A Hb of 8gm/dl in a bleeding or dehydrated patient may really be 5gm/dl when resuscitation is complete, and vascular volume is expanded, so blood transfusion may be indicated early.
Urea and Creatinine and Electrolytes may be helpful, but should be interpreted in the context of the clinical picture, and information about whether the patient has pre-existing renal failure.
Elevation of urea and creatinine may simply indicate dehydration and poor renal blood flow, or it may indicate acute or chronic renal failure. Fluid resuscitation should proceed whatever the cause, to ensure renal blood flow is improved.
Serum sodium, potassium, chloride and bicarbonate may be “normal” or “abnormal”. The first step in the acute abdominal emergency is again expansion of intravascular volume and fluid resuscitation. If renal function can be restored, the kidneys will correct the electrolyte disturbance.
Chloride and bicarbonate tend to balance each other - if one goes up the other goes down. Hypochloraemia (as in pyloric stenosis) will correct with normal saline infusion, but be made worse with Hartmann’s solution, because of the lactate, which is converted to bicarbonate. A low bicarbonate usually indicates metabolic acidosis due to poor perfusion, and corrects as the circulation improves.
Administration of bicarbonate is not often advisable, because it combines with hydrogen ions and results in formation of carbon dioxide which must be excreted by increased ventilation. Its acidosis-correcting effect is thus short-lived.
Coagulation profile must be checked to exclude coagulopathy in situations involving massive bleeding or sepsis.
Blood sugar (or urinalysis for glucose) should always be measured to allow correction in the diabetic, and to detect diabetic ketoacidosis masquerading as an abdominal emergency.
Arterial blood gases are the only accurate way of obtaining:
● PaO 2 (Oximetry is a substitute provided perfusion is good)
● PaCO 2 (End tidal CO 2 is a substitute but in the critically ill patient, there may be a wide gap between the ETCO 2 and the higher PaCO 2, not the normal 6mmHg)
● pH
● HCO 3 (which may differ from that measured with serum electrolytes)
● Identification of whether an acid-base disturbance is an acidosis or alkalosis, whether either is primarily metabolic or respiratory, and whether there is secondary compensation for the primary disturbance.
Chest X-Ray is often useful in patients with abdominal emergencies when history and examination are not clear-cut, particularly in obese patients. Look carefully for pneumothorax, haemothorax, effusion, evidence of stomach or bowel in the chest, abnormalities in the lung fields (basal atelectasis is common), size and outline of the cardiac shadow.
ECG may indicate ischaemia, atrial or ventricular enlargement, abnormalities of electrolytes (as in the peaked T waves of hyperkalaemia), arrhythmias.
Resuscitation goes hand in hand with assessment
● Airway problems such as in severe facial injury must be managed before induction of anaesthesia.
● Oxygen should always be given to the critically ill patient.
● Breathing problems such as asthma or pneumothorax must be treated before induction of anaesthesia.
● Circulation problems such as hypovolaemia or cardiac tamponade must be treated before induction of anaesthesia.
● Other emergencies, such as hyperglycaemia and electrolyte or acid-base abnormalities must have treatment commenced before induction of anaesthesia.
● Consider the need for a nasogastric tube. Decide when to insert the urinary catheter.
Resuscitation must be aggressive before and during anaesthesia. The only excuse for induction prior to resuscitation is if the patient has a condition that cannot improve without surgery. This may include massive intra-abdominal haemorrhage. Even then, resuscitation must begin before anaesthesia is induced.
Which fluids should be used in resuscitation depends on the cause of the problem, and what is available. In an adult with intra-abdominal bleeding, the choice is clearly blood and plasma expanders such as Haemaccel or Gelafusin or Dextran, supported by crystalloids - normal saline or Ringer lactate (Hartmann’s) solution. In a patient with intra-abdominal sepsis, the same approach may be needed, but blood transfusion will depend on the haemoglobin level once vascular volume has been restored. In an adult with bowel obstruction who is not shocked, saline or Hartmann’s solution may be adequate. In an infant with pyloric stenosis, saline is required initially, and Hartmann’s solution will make the hypochloraemic metabolic alkalosis worse.
Choice of Anaesthetic technique(s)
General anaesthesia is the most commonly employed technique.
Advantages
- Protection of the airway and assurance of adequate ventilation.
- Rapid induction of anaesthesia with controlled depth and duration.
Disadvantages
- Loss of airway reflexes increases risk of aspiration.
- Adverse haemodynamic consequences of general anaesthetics.
Regional anaesthetic techniques for abdominal surgery include spinal, epidural, caudal and nerve blocks. Lower abdominal procedures (e.g. inguinal hernia repair) can be performed with regional anaesthesia techniques that produce a sensory level to T4-6.
·Epidural anaesthesia is performed usually by continuous catheter technique. A “single dose” technique is applicable for surgery of less than 3 hours duration.
·Spinal anaesthesia with either single-dose or continuous-catheter technique.
·Nerve blockscan also provide adequate anaesthesia for abdominal surgery.
Bilateral blockade of T8-12 intercostal nerves provides somatic sensory anaesthesia.
Blockade of the ilioinguinal, iliohypogastric, and genito-femoral nerves produces a
field block that is satisfactory for herniorrhaphy.
Advantages
- Maintenance of a patient’s ability to communicate symptoms (i.e. chest pain).
- Maintenance of airway reflexes.
- Profound muscle relaxation and bowel contraction provide optimal surgical exposure.
- Bowel blood flow increases as a result of complete sympathectomy.
- Postoperative analgesia can be provided with continuous-catheter techniques.
Disadvantages
- Local anaesthetic toxicity with intravenous (IV) injection.
- Patient cooperation necessary for institution of block and positioning during surgery.
- Failure necessitates intraoperative conversion to general anaesthesia.
- Regional nerve blockade may be contraindicated in patients with abnormal bleeding profile or localised infection at site of injection.
- Sympathectomy produces venodilation and bradycardia; these can precipitate profound hypotension. Unopposed parasympathetic activity causes the bowel to contract and may make construction of bowel anastomoses more difficult; this can be reversed with glycopyrrolate, 0.2 to 0.4mg IV.
- High-level thoracic blocks may compromise pulmonary function.
Combined techniqueuses an epidural anaesthetic along with a light general anaesthetic. This technique is commonly employed for extensive upper abdominal surgeries.
Advantages
- Epidural anaesthesia reduces the requirement for general anaesthesia; this minimises myocardial depression and may decrease emergence time and nausea.
- Combined techniques are particularly useful in reducing post-operative ventilatory depression and improving pulmonary function early after upper abdominal surgery.
Monitoring
The most important monitoring of the patient is clinical including pulse, blood pressure, colour, respiration in addition to monitoring the surgical field, blood loss, urine output and fluid input. Heart sounds are useful to monitor particularly in children.
The next important set of instrument monitors are pulse oximetry, end tidal CO2 monitoring, ECG and temperature.
If available, CVP monitoring may be a useful guide, particularly in the patient who you think has had adequate fluid/blood replacement, but who remains hypotensive. Supported by a high CVP reading, this may be an indication for adrenaline infusion rather than more fluid, provided all other causes of hypotension have been looked for (e.g. pneumothorax, excess anaesthetic agent).
Other forms of monitoring in the critically ill patient might include an arterial line for BP and blood gas sampling, and occasionally a pulmonary artery catheter, which may show that despite a high CVP, the left atrial pressure, as reflected by the pulmonary capillary wedge pressure, is low.
Neuromuscular function monitoring is helpful in those patients who do not breathe well after reversal of muscle relaxants.
In situations where they are available, monitoring of inspired and expired oxygen, nitrous oxide and volatile agent should be used. Airway pressure, tidal and minute volume measurements likewise should be used if available.
Management of Anaesthesia
Induction of Anaesthesia.Restoration of volume deficits before induction and careful titration of sedative premedications provide more haemodynamic stability.
Rapid-sequence inductionis required for all patients considered to have full stomachs.
Indications include:
a. Trauma; gastric emptying is delayed.
b. Bowel obstruction and ileus.
c. Symptomatic hiatal hernias.
d. Second or third trimester of pregnancy.
e. Significant obesity.
f. Ascites.
Maintenance of Anaesthesia
Maintenance of anaesthesia may be achieved with nitrous oxide, oxygen and a volatile agent. If there is no nitrous oxide or it is contra-indicated, an air/oxygen mixture and volatile agent can be used. If there is no oxygen, just air and volatile agent, bearing in mind that the amount of the anaesthetic agent required will be higher than if it is used with nitrous oxide. If there is no air, oxygen and volatile agent can be used.
The maintenance phase requires observation and monitoring of the patient, and of the surgery, with particular attention to fluid and blood loss. If major surgery is proposed, or if the patient was dehydrated or hypovolaemic, measurement of urine output is a good guide to renal perfusion.
Fluid management requires administration of maintenance fluids and replacement of both deficits and ongoing losses.
1. Bleeding should be estimated both by direct observation of the surgical field and suction traps and by weighing sponges. Blood loss concealed beneath drapes or within the patient may be impossible to estimate.
2. Bowel and mesenteric oedema can result from surgical manipulation or intestinal tract disease.
3. Evaporative losses from peritoneal surfaces are directly related to the area exposed. Fluid replacement is guided by clinical judgment or invasive monitoring; as a rough estimate, 10 to 15 ml/kg per hour may be required.
4. Abrupt drainage of ascitic fluid with surgical entry into the peritoneum can produce acute hypotension from sudden decreases of intra-abdominal pressure and pooling of blood in mesenteric vessels. Postoperative reaccumulation of ascitic fluid can produce significant fluid losses.
5. Nasogastric and other enteric lossshould be quantified and replaced appropriately.
Muscle relaxationis required for all but the most superficial intraperitoneal operations; sufficient relaxation is critical at abdominal closure, since bowel distention, oedema, or organ transplantation increase the volume of abdominal contents. A non-depolarising muscle relaxant and intermittent positive pressure ventilation allows the best conditions for the surgeon. If there are no relaxants, controlled or assisted ventilation will still assist the surgeon.
Use of nitrous oxide(N20) may cause bowel distention. Because N20 is more soluble than nitrogen, it diffuses into bowel lumen faster than nitrogen can diffuse out; intraluminal gas volume doubles in approximately 10 minutes when 60% N20 is inspired. Distention can make closure difficult, and increased intraluminal pressures may cause impaired perfusion of obstructed bowel. The use of N20 is relatively contraindicated in closed-loop bowel obstructions or during construction of anastomoses in unprepared bowel.
NG tubesare frequently placed in the perioperative period. Preoperative placementis indicated for decompression of the stomach, especially in trauma victims or patients with obstructed bowel. Although suction via a large-bore NG tube can reduce the volume of gastric air and contents, it does not eliminate these entirely. NG tubes may compromise mask fit and provides a route for reflux of gastric contents past the lower esophageal sphincter. Before induction, suction should be applied to NG tubes; during induction, tubes should be allowed to drain. Cricoid pressure may prevent reflex when a NG tube is present. Intraoperative placementis required to drain gastric fluid and air during abdominal surgery.
NG and orogastric tubes should never be placed with excessive force; lubrication and head flexion facilitate insertion. Tubes can be directed into the esophagus using a finger in the oropharynx or with McGill forceps under direct visualisation with a laryngoscope. If these methods fail, a large, split endotracheal tube (9.5cm or larger) can be used as an introducer: the split endotracheal tube is introduced orally into the esophagus and the NG tube passed through the lubricated lumen of the tube into the stomach; the split tube is then removed while stabilising the NG tube.
Complicationsof NG tube insertion include bleeding, submucosal dissection in the
retropharynx, or placement in the trachea. Intra-cranial placement has been described in patients with basal skull fracture. The NG tube should be secured carefully to avoid excessive pressure on the nasal septum or nares, which may cause ischaemic necrosis.
Common Intraoperative problemsassociated with abdominal surgery include the following:
a. Pulmonary compromise,often caused by retraction of abdominal viscera to improve surgical exposure (insertion of soft packs or rigid retractors), insufflation of gas during laparoscopy, or Trendelenberg positioning. These maneuvers may elevate the diaphragm, decrease FRC, and produce hypoxaemia. Application of positive end-expiratory pressure (PEEP) may counter these effects.
b. Temperature control.Heat loss in open abdominal procedures is common.
c. Haemodynamic changes as a result of bowel manipulation(i.e. hypotension, tachycardia and facial flushing).
d. Opioids may aggravate biliary tract spasm.Although uncommon, opioids may produce painful biliary spasm in some patients when administered as a premedication or epidurally. Spasm can be reversed with naloxone; nitroglycerin and glucagon also relieve spasm by nonspecific smooth muscle relaxation.
e. Faecal contaminationoccurs from perforation of the gastrointestinal trace. Infection and sepsis can progress rapidly.
f. Hiccupsare episodic diaphragmatic spasms that may occur spontaneously or in response to stimulation of the diaphragm or abdominal viscera. Potential therapies include:
- increasing depth of anaesthesia to ameliorate the reaction to endotracheal, visceral, or diaphragmatic stimulation.
- Removal of the source of diaphragmatic irritation, such as gastric distention.
- Increasing the degree of neuromuscular blockade may decrease the strength of spasms.
Complete diaphragmatic paralysis is difficult to achieve and may be possible only with doses of relaxants in excess of those required for relaxation of abdominal musculature.
- Chlorpromazine, rarely used intraoperatively, can be titrated in 5-mg IV increments.
Anaesthetic considerations for specific abdominal procedures
Gastric surgery is usually performed with general anaesthesia or combined general anaesthesia and epidural block. The high likelihood of aspiration in these patients necessitates a rapid sequence or awake intubation. Large third-space losses and potential for hemorrhage should be anticipated.
Gastrostomy can be performed through a small, upper-abdominal incision or percutaneously with an endoscope. Local anaesthesia with sedation is often adequate in the debilitated elderly patient, although some patients require general anaesthesia.
Intestinal and peritoneal surgery. Indications for small bowel resectioninclude penetrating trauma, Crohn’s disease, obstructing adhesions, Meckels diverticulum, carcinoma, or infarction (from volvulous, intussusception, or thromboemboli). Patients are usually hypovolaemic and are at risk for having a full stomach.
Appendectomyis performed through a small lower-abdominal incision. Fever, poor oral intake, and vomiting may produce hypovolaemia; IV hydration before induction is indicated. In rare cases when sepsis and dehydration are absent, a regional anaesthetic may be appropriate; otherwise, general anaesthesia with rapid-sequence or awake intubation is necessary.
Colectomy or hemicolectomyis used to treat colon cancer, diverticular disease, Crohn’s disease, ulcerative colitis, trauma, ischaemic colitis, and abscess. Emergency colectomy on unprepared bowel carries a high risk of peritonitis from fecal contamination. Some emergencies involving the colon are treated with an initial diverting colostomy followed later by bowel preparation and elective colectomy. Patients must be evaluated for hypovolaemia, anaemia, and sepsis. All emergency colectomies and colostomies should be treated as if at risk for full stomach. Combination general and regional anaesthetics are preferable.
Perirectal abscess drainage, haemorrhoidectomy, and pilonidal cystectomyare relatively noninvasive and brief procedures. Pilonidal cysts are usually excised with the patient in the prone position; abscess drainage and haemorrhoidectomy can be performed with the patient either prone or in lithotomy position. If general anaesthesia is employed, deep planes of anaesthesia or use of muscle relaxants may be necessary to achieve adequate sphincter relaxation.
Intubation is required to provide general anaesthesia for prone patients. Hyperbaric spinal anaesthesia is used for procedures in lithotomy position, while hypobaric spinal is useful for the flexed prone (jackknife) or knee-chest position; caudal block is applicable with either position.
Inguinal, femoral, or ventral herniorrhaphiescan be performed with the patient under local anaesthesia, regional anaesthesia, (spinal, epidural, caudal, or nerve block), or general anaesthesia. Maximum stimulation and a profound vagal response may occur during spermatic cord or peritoneal retraction. If general anaesthesia is selected, either a mask technique (e.g. laryngeal mask airway) or deep extubation should be considered to decrease coughing on emergence, which can strain the hernia repair.
Biliary tract procedures. Cholecystectomyis a common procedure performed either as open laparotomy or by laparoscopic technique. General anaesthesia is required for either technique.
Postoperative Care
Care in the Recovery Room must equal that during anaesthesia until the patient is capable of looking after his/her own airway and breathing and is fully conscious. The patient in Recovery should continue to receive oxygen, have continuous monitoring of airway, breathing and circulation, and be given analgesia as required. The critically ill and any unstable patients should be considered for admission to a high dependency unit 24-48 hrs.
The anaesthetist is often the best resource a surgeon has for advise on post-operative problems such as pain, management of nausea and vomiting, fluid and electrolyte replacement.
SELF-ASSESSMENT QUESTIONS
Define “massive transfusion”. What are the physiological effects of massive transfusion? How would you manage massive transfusion?
TRAUMA, BURNS AND ABDOMINAL SURGERY CASE STUDIES
Case No 14.1
Tunga is a 29 year old lady who weighs 130 kg. She has been admitted for a cholecystectomy.
Describe the problems associated with obesity and anaesthesia.
How would you modify your technique for her obesity?
Discuss the potential complications of upper abdominal surgery for this patient.
What are the options for post-operative pain relief?
What are the physiological changes, which occur when a patient is positioned head down?
The surgery proceeds uneventfully and you reverse the patient and extubate her when you consider she is able to maintain her own airway. You receive a call from the recovery room 20 minutes later because the lady is un-rousable and having difficulty maintaining oxygen saturations above 90%.
Discuss the possible aetiology.
Describe your management.
Case No 14.2
Tulga has been admitted to hospital following a GI bleed. Tulga is a 40-year-old Mongolian male who admits to frequent vodka drinking. His oxygen saturation in air is 91% and increases to 93% when breathing O2 at 6lpm via a face-mask. He is jaundiced and has been commenced diuretics for ascites. The surgeons are planning on taking him to theatre for a laparotomy.
Discuss the possible causes for his jaundice.
What are the implications for anaesthesia and surgery?
How will you reduce the risk of aspiration?
Case No 14.3
Ganbold is found unconscious in his ger. He has suffered significant burns
What clinical features are most important for deciding his immediate and early management?
Discuss fluid management for burns victims.
Final Objective: This module is designed to give you a better understanding of the latest developments in managing trauma/burns, their physiological effects and the anaesthetist’s role in trauma/burns management.
Enabling Objective: To achieve this goal, you should know:
- The pathophysiology of burns
- How to accurately assess the extent and physiological effect of a burn
- Resuscitate the burn patient
- The anaesthetic considerations of the burn patient.
- Identify priorities in the treatment of individuals and groups (triage).
- Demonstrate the ability to assess, resuscitate and facilitate further management.
- Describe the principles and practice of anaesthesia for the injured patient, including burns.
- Outline the factors, which predispose patients to regurgitation and aspiration of gastric contents.
- Describe the perioperative problems associated with abdominal surgery.
- Developing Anaesthesia Chapters 14, 42 & 44
- Oxford Handbook of Anaesthesia Chapters 20 & 34
- Airway Seminar 2009.
Introduction
Trauma is the leading overall cause of death in the age group from birth to 30 years. For every death, two people suffer permanent disability.
Patients suffering from multiple injuries are commonly known as major trauma victims. Best outcomes are obtained for these patients by having in place a well-developed multi-disciplinary, trauma care system.
Assume that all multiple trauma patients have a cervical spine injury, a full stomach and are hypovolaemic.
Trauma Teams Victims of major trauma are best treated by a well organised and trained team made up of staff competent in assessing and treating the spectrum of life- threatening injuries commonly seen. An experienced physician anaesthetist, possessing airway and resuscitation skills and confidence in dealing with unconscious patients, is a vital member of the team.
Whenever possible both a general surgeon and an orthopaedic surgeon should be members of the trauma team. Their presence can reduce delays in the accident department, improve the early diagnosis of life threatening injuries and lead to earlier surgery when required. Having both specialists present prevents one doctor becoming overwhelmed by complex problems in an unstable patient. The team should include a radiographer when available. Staff should wear adequate protection including gowns, gloves and eye protection. It is often possible for the team to be given prior warning of a casualty arriving, thereby allowing time for preparation. Accident & Emergency departments should have a resuscitation area set aside to receive major trauma victims with anaesthetic airway equipment and drugs, intravenous fluids with blood giving sets and blood warmers. Surgical sets should include equipment for the following procedures: urinary catheterisation (including suprapubic), peritoneal lavage, pleural drainage (chest drains sets with underwater seal) and needle and surgical cricothyrotomy. Specific provision should be made for children with appropriate sizes of equipment to deal with all ages and equipment for intraosseous fluid.
Methods of Managing Trauma
A multidisciplinary approach is required in the management of major trauma and the same technique for assessment and treatment of each patient should be followed. Most modern trauma systems have a fairly rigid protocol to follow, thus reducing the opportunity for misdiagnosis.
The most widely taught system is the Advanced Trauma Life Support (ATLS) Program for Physicians, devised and disseminated by the American College of Surgeons.
Timing of death resulting from trauma
The mortality due to injury occurs during one of the following time periods:
The first peak of death occurs at the time of the injury. It may be instantaneous or within the first few minutes and is due to an overwhelming primary injury to major organs or structures such as brain, heart or great vessels. In most situations these injuries are irrecoverable, although rapid treatment and transfer may salvage some patients. Primary prevention (e.g. seatbelts) has a major role in reducing the incidence of these deaths.
The second peak lasts from the end of this first period to several hours after the injury has occurred. It is during this time that many causes of morbidity and mortality are preventable by avoidance of a secondary injury due to hypoxia, haemorrhage or any process that leads to inadequate tissue perfusion. Reversible conditions may include intracranial haematomas, major haemorrhage from viscera, bones and vessels or pneumothoraces. Even with moderate facilities many lives can be saved by simple measures.
The third peak of death occurs days or weeks after the injury from sepsis and multiple organ failure. Advances in intensive care treatment may reduce deaths but improvements in the initial management on admission will also reduce morbidity and mortality.
Initial evaluation of the trauma patient
The patient suffering multiple traumas must be thoroughly assessed on admission so that life-threatening injuries can be immediately identified and corrected. The condition of the patient must be stabilised and plans made for further treatment of their injuries. The team leader is responsible for assessing the patient and coordinating the work of the other members of the team, whose role is to treat the injuries as directed by the leader.
All trauma cases should receive:
- Primary survey (assessment) and resuscitation
- Secondary survey
- Definitive treatment
Primary Survey and Resuscitation
The purpose of the primary survey is to diagnose immediate life threatening conditions. These must be treated as soon as they are discovered before continuing the survey. The survey is planned as follows:
Airway control with cervical spine protection.
Breathing.
Circulation and control of haemorrhage.
Disorders of the central nervous system.
Exposure of the whole body.
During the course of the primary survey, any deterioration in the patient’s condition must be managed by reassessing the patient from the start of the survey.
Airway control and cervical spine protection.
Always ensure that the patient has an unobstructed airway. If the patient can answer questions appropriately, then it is unlikely that there is any immediate threat to the airway. Noisy or laboured respiration or paradoxical respiratory movements (when the movements of the chest and abdomen are not in phase) are evidence of airway obstruction. Vomit, blood or foreign material in the mouth must be removed manually or with a sucker. Sometimes a simple chin lift and or jaw thrust is all that is required to prevent the tongue of an unconscious patient obstructing the airway, however often patients require advanced airway techniques. An oropharyngeal/nasopharyngeal airway may be beneficial but must be the correct size and inserted carefully.
Any patient with a possible cervical spine injury (unconscious, mechanism of trauma, neck pain or neurological deficit) must have their neck immobilised in a neutral position to prevent secondary spinal damage. Cervical spine damage is likely with deceleration injury, hyperflexion or extension injury or any blunt injury above the clavicles. A fracture of the first rib seen on chest X-ray indicates high-energy transfer and should always raise suspicion of cervical injury as well as intrathoracic damage. When available a closely fitting hard cervical collar should be applied with sand bags placed on either side of the head and the patient immobilised on a spine board. Soft collars are ineffective for immobilising the neck.
Intravenous anaesthesia/muscle relaxation (rapid sequence induction) should only be used by an experienced anaesthetist when successful intubation of the trachea with inline stabilisation of the cervical spine can be guaranteed. If sever facial disruption or anatomical disorders make intubation unlikely, then a cricothyrotomy should be performed.
Breathing.
The patient must be assessed for tracheal deviation or unequal chest expansion. Pulse oximetry is a valuable monitor of adequate perfusion and arterial oxygen saturation. High concentration oxygen should be administered to every patient.
The following life threatening respiratory conditions need immediate treatment:
Tension pneumothorax
Massive haemothorax
Flail chest
Open chest wound
Disruption of the tracheobronchial tree.
A tension pneumothorax is suggested by a rapid respiratory rate, mediastinal (tracheal) shift away from the affected side, and hyper-resonance and reduced breath sounds on the affected side. It should be treated initially by needle decompression of the pleural cavity at the second intercostal space in the mid clavicular line, followed by formal pleural drainage with an intercostal catheter/underwater seal drain. It is important to remember that a simple pneumothorax may be changed into a tension pneumothorax with positive pressure ventilation. A chest drain should be inserted prophylactically before positive pressure ventilation.
A massive haemothorax is suggested by reduced breath sounds, dullness to percussion and a shift of the mediastinum away from the affected of the above side often accompanied by cardiovascular instability. It should be treated with formal pleural drainage and if the initial volume of blood exceeds 1500 ml or bleeding continues at a rate greater than 200 ml/h, a thoracotomy is indicated.
The anaesthetist must be aware that endobronchial intubation can mimic both. The endotracheal tube position must be checked before making a diagnosis of pneumothorax or haemothorax.
Flail chest means that part of the chest wall is able to move independently to the remainder of the chest and occurs when ribs are fractured in at least two places. The flail segment falls during inspiration while the rest of the chest rises. It is always associated with significant pulmonary contusion and hypoxia. If respiratory failure develops despite oxygen therapy and adequate analgesia (preferably epidural or intercostal blocks), the intubation and positive pressure ventilation is required.
An open chest wound needs covering and sealing on three sides immediately. The flapping motion of the free edge of the dressing forms a one-way valve , which prevents air being sucked into the pleural cavity from outside.
This should be followed by formal pleural drainage and possibly thoracotomy. Once the pleural cavity is drained, the wound may be closed.
Patients with a major disruption of the tracheobronchial tree need immediate endotracheal or endobronchial intubation and thoracotomy. The condition is most often diagnosed by the presence of pneumomediastinum, pneumopericardium or surgical emphysema. Minor tears may sometimes be treated conservatively.
Circulation.
The circulation is initially assessed by palpating the pulses, assessing skin colour and capillary refill, conscious state and by measuring the blood pressure. Intravenous access should be obtained with at least two large bore cannulae. Blood should be taken at the time of cannulation and crossmatch blood ordered as a priority.
Any major haemorrhage that is visible should be controlled by direct pressure. Tourniquets should not be used. Penetrating objects should be left for formal surgical exploration.
The most common cause of shock in multiply injured patients is haemorrhage. Blood loss from a fractured humerus may be up to 800ml, from a fractured femur 200ml and from a fractured pelvis 3000ml. Intra-cranial haemorrhage is insufficient to cause shock in an adult.
Hypovolaemia is often categorised into 4 classes.
Class of hypovolaemia
Class
I
Class
II
Class
III
Class
IV
Blood Loss:
% Circulating volume
<15
15-30
30-40
>40
Blood Loss:
Volume (mls in adults)
<750
750-1500
1500-2000
>2000
Pulse
Normal
100-120 bpm
120 bpm Weak
>120 bpm Very weak
Blood Pressure:
Systolic
Normal
Normal
Low
Very Low
Blood Pressure:
Diastolic
Normal
High
Low
Very Low
Capillary Refill
Normal
Slow
Slow
Absent
Mental State
Alert
Anxious
Confused
Lethargic
Respiratory Rate
Normal
Normal
Tachypnoeic
Tachypnoeic
Urine Output
>30 mls/hr
20-30 mls/hr
5-20 mls/hr
<5 mls/hr
It must be stressed that there is variation from this guide, particularly in the elderly, in those with previous medical conditions or those who are taking cardiovascular medications who all tolerate hypovolaemia poorly. It must be remembered that anaesthesia will obtund the compensatory sympathetic response to hypovalaemia and may cause cardiovascular collapse.
Volume resuscitation begins immediately with the establishment of venous access. Most trauma patients are hypovolaemic and the restoration of the circulating volume is always the first priority of fluid management. The second priority is the restoration of blood carrying capacity followed by the normalisation of coagulation status.
The amount and type of fluid administered will depend on the type and extent of injury. Usually 10-20 ml/kg of colloid or 20-30 ml/kg of crystalloid is administered as an initial bolus and the patient is reassessed and boluses continued until the patient is clinically resuscitated. Whenever possible the fluid should be warmed to prevent further cooling of the patient.
Hypotension may also result from cardiac failure which is, however, rare in trauma patients and is likely to be due to cardiac injury, either myocardial contusion (which should be expected in blunt thoracic trauma), or cardiac tamponade (which should be suspected in penetrating chest injury when shocked patients do not respond to fluid resuscitation and the degree of hypotension is greater than the apparent blood loss). Cardiac tamponade will cause a raised jugular venous pressure, muffled heart, hypotension, tachycardia and pulsus paradoxus. Cardiac tamponade needs emergency treatment by needle pericardiocentesis followed by formal surgical exploration and repair.
Disorders of the central nervous system.
The central nervous system should be quickly assessed by checking the patient’s level of consciousness, spinal cord function and pupillary response to light. Conscious level is assess by recording the patient’s eye opening and motor response to graded stimuli (spontaneous, in response to direct questioning, pain or no response). All four limbs should be tested to assess the spinal cord function.
Exposure.
All patients with multiple injuries should be completely undressed to allow a thorough survey of injuries. Clothes may be cut off if necessary to minimise undesirable patient movement. However, the patient must not be allowed to become hypothermic and should be kept covered when possible and the resuscitation room should be warm. Injured children lose heat rapidly when exposed.
During the course of the primary survey, the five most important rules to remember are:
Airway breathing circulation
The patient should be repeatedly reassessed, particularly if clinical signs change.
Any immediately life-threatening condition should be treated without delay.
Penetrating wounds and foreign bodies must be left for formal surgical exploration.
Any external bleeding should be stopped by using direct pressure.
Secondary Survey
Following the initial survey and resuscitation, the patient should undergo a thorough secondary survey with the aim of documenting any other injuries. During this survey the basics of the primary survey (airway, breathing and circulation) must be regularly reassessed. Tetanus immunisation and prophylactic antibiotics can be administered if necessary. A history should be obtained and X-rays of the lateral cervical spine, chest and pelvis taken. (Remember however that lateral cervical spine X-rays may fail to reveal up to 20% of cervical spine injuries).
History.
A full history is required, particularly allergies, medications and tetanus immunity, previous medical history, fasting status and the events leading to the injury.
Vital information can be gained from the history or the events leading to the injury and particular attention should be paid to the mechanism of injury. The extent and severity of injury is related to the amount of energy transferred to the patient. In blunt trauma, commonly associated with road traffic accidents and falls, there are a number of situations, which are associated with life-threatening injuries:
- Road traffic accidents:
- Where speeds were in excess of 60 km/h
- Where the victim was ejected from the vehicle
- Where other victims were killed
- Where there was severe disruption of the vehicle passenger compartment
- A fall greater than 3 m
- In penetrating trauma from gunshot the amount of tissue damage increase with the velocity of the bullet (particularly if the bullet does not exit the body so that all of it’s energy is transferred to the victim).
“Top to toe”
Head. The Glasgow Coma Scale score should be assessed. The scalp should be palpated for fractures, lacerations and other deformities. Adults rarely lose a significant amount of blood from scalp wounds but bleeding should be stopped. Any injury to or around the eye should be noted. Periorbital and/or subconjunctival haemorrhage may indicate a base of skull fracture. Blood or cerebrospinal fluid coming from the ears or nose may also indicate a base of skull fracture.
Facial fractures must be sought by careful palpation, but only treated at this stage if likely to compromise airway patency. Swelling or haemorrhage associated with such fractures may cause delayed respiratory obstruction and must be anticipated. Movement of the maxilla indicates a middle third fracture.
Neck. The patient should be asked if they have any neck pain. With an assistant performing in-line immobilisation, the tapes, sand bags and neck collar should be gently removed and the neck examined for lacerations, swellings, tenderness or deformity of the cervical spine. Penetrating neck wounds must be explored under general anaesthesia.
The cervical spine should have lateral, antero-posterior and odontoid peg views. A lateral X-ray of the cervical spine must show all the vertebrae including the body of the first thoracic vertebra. X-rays alone cannot detect all injuries to the cervical spine and much depends on the history and examination.
Chest. The entire chest must be examined for signs of injury. This includes palpating for fractures of the clavicles and ribs and the presence of subcutaneous emphysema. Percutaneous drainage of haemo/pneumothoraces must be performed when they are diagnosed or strongly suspected. Deceleration injuries may cause tracheobronchial injury, transection of the thoracic aorta, cardiac injury and diaphragmatic rupture.
Complete aortic transection is immediately fatal. Incomplete aortic transection is suggested by the history, chest X-ray signs of widening of the mediastinum, pleural capping (fluid shadow at the apex of the lung) and a shift of the trachea to the right and/or inferior displacement of the left main bronchus.
Cardiac contusion may be suggested by the history, inadequate response to intravenous fluids, high central venous pressure and ECG changes. Investigations include echocardiography, which may show abnormal heart wall movement and/or a pericardial effusion. Echocardiaography is also useful in diagnosing heart valve rupture.
Diaphragmatic rupture is commoner on the left side and is diagnosed by history, dyspnoea and abdominal contents visible on chest X-ray within the thoracic cavity. A right-sided diaphragmatic hernia is more difficult to diagnose. If a diaphragmatic hernia is suspected, a radio-opaque nasogastric tube should be inserted and the chest X-ray repeated. Surgical repair is required.
Abdomen. The abdomen must be inspected for signs of injury and the presence of free intraperitoneal fluid. Ultrasound can allow rapid assessment of many intraabdominal injuries. Penetrating wounds should be examined at laparotomy if they breach the muscle. Eviscerated bowel must be covered with packs soaked in warm saline. The pelvis must always be X-rayed. Blood at the urethral meatus or scrotal haematoma indicates urethral injury in the male. In this situation a supra-pubic catheter should be inserted. Otherwise a urethral catheter should be inserted, and the presence of any obvious or microscopic haematuria sought. A rectal examination may also reveal blood or pelvic fractures, and an assessment of anal tone can be made. A lax anal sphincter may indicate that spinal cord injury has occurred. The stomach may dilate acutely in trauma patients, and may need decompression using a nasogastric tube (or an oro-gastric tube if a base of skull or mid face fracture is suspected). Vaginal examination may show a pelvic fracture or breach of the vaginal vault.
If assessment is difficult or equivocal, then diagnostic peritoneal lavage is indicated. It should not be performed if there is a need for urgent laparotomy i.e. penetrating trauma, unexplained hypovolaemia, extruded bowel or radiological evidence of intra-abdominal trauma.
Limbs. Fractures, wounds and discolouration must be noted. Check pulses in all limbs even if no fracture is suspected. Fractures compromising circulation must be rapidly reduced to prevent distal ischaemia. Fractures should be splinted to reduce pain and the risk of fat emboli.
Foreign material and devitalised tissue should be removed. Large blood losses may be associated with long bone and particularly pelvic fractures, but in a shocked patient they must not be assumed to be the only cause. Early fixation of these fractures may reduce blood loss, accelerate mobilisation and reduce the severity of fat embolism. Signs such as increased swelling, pain and altered sensation suggest that the patient may have developed a compartment syndrome, which requires urgent fasciotomy.
Spine. Hypotension with bradycardia is unusual in hypovolaemia but if present does not exclude haemorrhage, especially in the elderly. It is however, more likely to be due to spinal cord damage in a patient with a history suggestive of spinal cord injury. Fluid replacement should be guided by careful monitoring to avoid over fluid resuscitation. Other indicators of cord damage are acute urinary retention, diaphragmatic respiration, priapism lax anal sphincter and flaccid paralysis of the limbs.
The cervical and thoracolumbar regions are most commonly affected by trauma and appropriate X rays must be taken. The patient must be log rolled and the entire back examined.
The further treatment will depend on the injuries detected, with priority given to those which are most severe/life threatening.
Transport. The transfer of the patient with multiple traumas can be hazardous. In all but the most desperate situations, the condition of the patient should be stabilised prior to transfer. The level of monitoring must be maintained during transport, adequate resuscitation equipment and drugs should be available, hypothermia avoided and the receiving carers must be warned of the condition of the patient. The staff that accompanies the patient must be experienced in the care of critically ill patients.
Anaesthesia for Trauma.
As with anaesthesia for all patients, the key to successful trauma anaesthesia is the adequate assessment and pre-operative resuscitation of the patient. In all but the most urgent surgery, there is sufficient time for this to occur.
The safe fasting time prior to anaesthesia after trauma is uncertain. In the patient undergoing immediate or early surgery (< 12 hours) operation the most important time interval is that between their last meal and the injury, as after the injury gastric emptying may cease. In those having surgery after a period of stabilisation and observation on the ward, the patient is often assumed to have an empty stomach if they are not in severe pain or have no other reasons to delay gastric emptying.
Preoperative assessment. All injuries must be found. If the patient has been admitted using the trauma assessment method above, then it is unlikely that serious injuries will be missed. If the patient has not had a trauma assessment, the anaesthetist must thoroughly examine he patient from head to toe. In addition a specific anaesthetic assessment should be performed. The appropriate investigations will depend on the injuries sustained and the operation planned. A blood crossmatch must be performed. Premedication is usually not necessary if the patient is kept pain free. Pre-operative antibiotics and tetanus vaccination are usually required.
A variety of methods of pain relief are available including nerve blocks (e.g. femoral nerve block), opioids paracetamol, non-steroidal anti-inflammatory drugs and inhaled analgesics (e.g. methoxyflurane and nitrous oxide). Opioids are best administered intravenously or by sub-cutaneous injection in small increments until acceptable analgesia is obtained. Nitrous oxide is best avoided in patients with chest trauma who may have a pnuemothorax or in scuba diving accidents.
Those patients with a thoracic injury should be investigated for the presence of fractured ribs as well as haemo- or pneumothoraces. If positive pressure ventilation is to be used, then they will require an intrapleural underwater seal drain to prevent the development of a tension pneumothorax during anaesthesia. Possible cardiac contusion must not be overlooked. It may present as persistent hypotension despite aggressive fluid replacement. A 12 lead ECG recording may assist in the diagnosis.
Hypovolaemia must be corrected before general or regional (spinal/epidural) anaesthesia. All anaesthesia may reduce the sympathetic nervous system activity, which is preventing hypotension in the hypovolaemic patient, causing a sudden and large drop in blood pressure. Patients should ideally be normotensive without a tachycardia before proceeding with anaesthesia. Even ketamine which usually does not cause a fall in blood pressure may do so is severely injured patients.
Care must be taken not to move a suspected cervical spine injury during transfer, positioning and airway manoeuvres (in-line stabilisation). Depolarising neuromuscular blocking agents (suxamethonium) may cause a life threatening rise in serum potassium in patients with burns, spinal cord damage or severe muscle atrophy and can only be safely used in the first 24 hours after the injury. Patients with head injury will require careful consideration of blood pressure and intracranial pressure control. Ketamine raises ICP.
Surgery for major trauma may be long with significant blood loss. The anaesthetist must continue to monitor blood loss and must administer appropriate fluids (crystalloid, colloid, blood, blood products) to prevent hypovolaemia, anaemia and coagulopathy. Appropriate fluid management can be helped by frequent laboratory investigations. The patient is also at risk of hypothermia.
In addition the patient must be observed carefully for any changes in vital signs which are unexpected and which might be the result of an undiagnosed injury (for example hypotension caused by undiagnosed intra-abdominal injury during an operation to repair a fractured femur). Good communication between the surgeon and anaesthetist is essential.
Unexplained hypoxia in the perioperative period where there is a long bone or pelvic fracture may be due to fat embolism associated with the release of intramedullary fat into the venous circulation from the fracture site. This can occur at any time following fracture, but is more common if surgical fixation is delayed for longer than 8 hours. The lung injury is characterised by capillary leak leading to pulmonary oedema (this occurs in the absence of heart failure). Hypoxia is always present and respiratory failure is common. The lung injury can be associated with systemic capillary injury commonly affecting the cerebral circulation, leading to confusion and decreased conscious state. A petechial rash is usually present over the trunk and conjunctiva. Renal impairment can occur. Treatment of fat embolism involves respiratory support with oxygen therapy and ventilation, and circulatory and renal support if required.
The key to successful trauma management involves prior preparation of the resuscitation room and creation of a trauma team in which the anaesthetist plays a vial role. The trauma team should be co-ordinated by a leader who should follow a primary survey and resuscitation, a secondary survey once the patient has been stabilised and prompt initiation of definitive treatment. A full history should identify mechanisms of injury. Anaesthesia for the trauma patient must involve a full assessment of the actual and potential injuries with the appreciation that resuscitation is often ongoing and that the patient’s condition can change dramatically.
The Burn Injury.
Burn injury can result from many causes; the majority of cases are due to thermal, chemical and electrical injuries. The commonest cause of death is by smoke inhalation.
Deep thermal injury destroys skin, the body’s barrier to the external environment. Skin plays a vital role in thermal regulation, fluid and electrolyte homeostasis, and protection against bacterial infection. Significant heat loss, massive fluid shifts and protein losses, and infections commonly occur in patients with severe thermal injuries. There is also a diffuse alteration in the permeability of cell membranes to sodium, resulting in generalised cellular swelling. Microvascular injury results from local damage by heat and from the release of vasoactive substances from the burned tissue. Therefore oedema occurs in both burned and unburned tissues.
In electrical burns current passage creates thermal energy that actually destroys tissue, particularly tissues with high resistance such as skin and bone. The course of the electrical current is often occult. The precise location and extent of tissue damage may not be revealed by physical examination.
In chemical burns the degree of injury depends on the particular chemical, its concentration, duration of contact, and the penetrability and resistance of the tissues involved. Some substances producing chemical burns, such as phosphorus, are absorbed systemically, producing significant and often life-threatening injury.
Infections and drug reactions may also cause extensive and life-threatening dermal injury.
ASSESSMENT
Burns are a form of trauma; thus the airway, breathing and circulation (ABCs) should be initially assessed. ‘ABCs’, gaining IV access, starting fluid resuscitation and providing pain relief are the cornerstones of the initial management. Potential airway compromise will be suggested by the history, facial burns, soot staining around the nostrils, singed nasal hairs etc.
The size of the burn should be estimated as a percentage of the total body surface area (%TBSA) and is an important guide to the severity of the burn. The ‘Rule of Nines’ guides estimations in patients over 14yrs of age:
Adults. The head and both of the upper extremities represent 9% TBSA each. The anterior trunk, posterior trunk, and both lower extremities represent 18% TBSA each.
Infants and children. Because of the different proportions of body surface area relative to patient age, reference must be made to the proper burn chart when calculating %TBSA to avoid significant errors. Another practical method to estimate %TBSA is that the area of the patient’s hand covers about 1% TBSA.
The depth of the burn is important for the planning of therapy (i.e. conservative management vs. excision and grafting). Erythema is not included in the estimate of the burned area. Nevertheless these areas, rather like sunburn, may be painful but will not be blistered and will heal normally without treatment. Superficial partial-thickness, deep partial-thickness and full thickness areas are included in the estimated area. The distinction between superficial and deep is of importance as the former has a better prospect of healing without scarring. Under resuscitation can cause deterioration of burned areas to a more severe grade.
Burn depth is difficult to determine visually; however there are some useful guidelines. The area under a partial-thickness burn usually has normal or increased sensitivity to pain and temperature and blanches with pressure. A full-thickness burn is anaesthetic and does not blanch.
Complex burns include destruction of tissues deep to the skin such as tendon, muscle and bone. Burns to the face, airway and perineum would also be included as complex burns.
Fluid loss. During the first 24 to 28 hours, massive evaporative losses and sequestration of fluid in the extracellular compartment (third spacing) are to be expected. Aggressive fluid repletion is necessary to prevent hypotension, hypo-perfusion, and shock. The composition of lost or sequestered fluid is very similar to that of plasma (i.e. the fluid has a high protein content).
Burns less than 10% TBSA do not normally require formal resuscitation, although admission for assessment, pain relief and investigation of circumstances may be required. Concurrent medical illness may make oxygen and fluids necessary even for <10%, for example in children with renal disease or with complex burns.
Burns greater than 10% and less than 30% may be classified as moderate in severity and will require oxygen, fluid resuscitation, pain relief and naso-gastric feeding. As severity approaches 30% TBSA, a systemic inflammatory response of pyrexia, raised white count and raised CRP in the absence of infection becomes more likely but only if the burn remains un-excised and only after 24-48 hours. For less severe burns, close to the time of injury, pyrexia and raised indices of infection may indicate true infection. Cultures should be taken and the wound inspected prior to starting antibiotic therapy. If pre-existing skin disease is present infection may occur early
Concomitant smoke inhalation and cutaneous burns between 10 and 30% indicates at least HDU based management.
Burns >30% TBSA represents a major injury where a systemic response is universal. Mortality is high if management is not optimal, even in young patients. The management of these more major burns involves Oxygen, fluids, feeding & pain relief as before, but with the need for invasive monitoring to guide therapy and for ventilation in a higher proportion of cases. Prophylactic antibiotics are not usually given except as part of a 'Selective Decontamination of the Digestive Tract', regimen in the more severe burns expected to be ventilated long term (in some units).
RESUSCITATION.
Aims to:
- Preserve life
- Maintain Organ function
- Ameliorate the injury
- Restrict surgery to necessity and functional restoration
- Limit Psychological damage
Thermal injury of the face and upper airway is a common occurrence, but burns involving the lower respiratory tract are infrequent. However, during a fire within a closed space or when heated noxious vapours are inhaled, inhalation injury may occur. This should be suspected in the presence of burns of the head or neck; singed nasal hairs; swelling of the mucosa of the nose, mouth, lips or throat; a brassy cough; or carbonaceous sputum. Both the upper airway and pulmonary parenchyma may be severely affected. Before airway oedema occurs, endotracheal intubation should be performed expeditiously. Continued swelling and distortion of the soft tissues progresses at a rapid rate, rendering intubation difficult, if not impossible.
The inhalation of toxic fumesmay directly damage the tracheobronchial tree and produce additional systemic effects. Combustion of polyurethane-containing products(e.g. insulation and wall panelling) releases hydrogen cyanide, a cell poison - leads to tissue hypoxia and death. The ambient oxygen concentration is reduced and the carbon monoxideconcentration is increased during a fire. Carbon monoxide poisoningoccurs when carbon monoxide combines with haemoglobin, displacing oxygen (carbon monoxide is bound more than 200 times as firmly as oxygen) and shifting the oxyhaemoglobin dissociation curve to the left. Tissue hypoxia ensues. Carbon monoxide toxicity may be difficult to diagnose because carboxyhaemoglobin appears similar to oxyhaemoglobin, and partial oxygen pressure (Pa02) measurements are in the normal range (unless there is underlying pulmonary parenchymal injury). Conventional pulse oximetry is unable to differentiate between oxyhaemoglobin and carboxyhaemoglobin.
Diagnosis is made by the direct measurement of carboxyhaemoglobin levels. The half-life of carboxyhaemoglobin is directly related to the inspired oxygen concentration (FiO2); it is 5 to 6 hours when breathing room air, but 30 to 60 minutes while breathing 100% oxygen. Hyperbaric oxygen at 3 atmospheres further reduces carboxyhaemoglobin half-life to 20 to 30 minutes. Thus treatment consists of supplemental oxygen (hyperbaric oxygen in severe cases) and supportive care until the carbon monoxide is eliminated. All burned patients, especially those burned while within a closed space, may have sustained some degree of tissue hypoxia with the thermal injury. Oxygen administration should begin at the scene. The inhalation of particulate matter(i.e. smoke and soot) results in mechanical obstruction of the airways.
Fluid Regimens
These are guides for appropriate replacement. All 'recipes', require monitoring and adjustment. The commonest now used is the Parkland formula. This is calculated having an accurate assessment of the burned area and the body weight, suggesting a volume of Ringer-Lactate (Hartmann’s Solution) given by:
2-4 mls per %TBSA per Kg body weight
This volume is given over the 24 hours following injury, half the (volume) being given over the first 8 hours from the injury. For example a 70 Kg Man with a 50% BSA Superficial partial thickness injury would require 7-14 (4x50x70/1000) litres over the first 24 hours. Experience suggests that those patients with smoke inhalation injury need still more fluids, as do those with extensive partial thickness burns.
If it has taken several hours for the patient to reach medical attention the first half may need to be given at a 'front loaded', accelerated rate for a couple of hours in order to catch up. It is important that under-resuscitation is avoided. The fluid should be warmed to ensure that the development of hypothermia doesn't complicate clotting function or cause inappropriate vasoconstriction.
Oliguria, haemoconcentration and hypotension are all signs of inadequate fluid administration under these circumstances.
Adequate cerebral function, brisk capillary refill, appropriate blood pressure and urine output in the range 0.5-1.0ml/kg/h output (1.0-2.0ml/kg/h urine output in children) suggest adequate resuscitation.
In larger burns and in patients with pre-existing impaired physiology, invasive monitoring with CVP or pulmonary artery flotation catheters may gauge adequacy of fluid replacement more effectively. These are best used early and removed before greater morbidity occurs due to infection.
Big burns themselves appear to have cardio-depressant effects. A decrease of cardiac output and arterial blood pressuremay occur in the immediate post burn period, despite adequate volume resuscitation. The cause of this phenomenon remains unclear but may be related to circulating factors that depress myocardial contractility.
Capillary integrityis re-established 36 to 72 hours after the initial injury, allowing resorption of fluid from the interstitial space and decreasing the need for fluid infusion. At this time, a “diuretic phase” may begin.
A hypermetabolic statedevelops 3 to 5 days following the burn injury. This may result in a two-to-threefold increase in cardiac output, which persists for weeks to months. However, Gram-negative sepsis may cause continued depression of cardiac output in some patients. Chronic post burn hypertensionmay be seen in young children (usually boys) who have sustained extensive burns. The syndrome usually develops within 2 weeks of injury and may result from elevated endogenous catecholamine levels.
Circumferential burns of the abdomenmay produce increased intra-abdominal pressure, which can reduce cardiac output by decreasing venous return.
Circumferential full-thickness burns of the thorax decrease chest wall compliance, which can lead to hypoxaemia and respiratory failure. Emergency escharotomies are frequently required.
If myoglobinuria is seen it is appropriate to aim for higher levels of urine output driven by osmotic diuresis with Mannitol. Up to 12.5 grams of Mannitol can be given per litre of resuscitation fluid (ATLS). This can give a sense of false security as urine output may be maintained while the patient remains dry overall. The overall fluid balance requires more careful monitoring under these circumstances.
Maintenance fluids appropriate to the age and weight of the patient are also required. In small children the use of Dextrose 4%/Saline 0.18% solutions will exaggerate the hyponatraemia. This will increase the likelihood of seizures. In any significant burn injury the use of the enteral route for administration of maintenance fluid as feed will reduce the tendency to low sodium and will minimise the loss of muscle to the catabolic response over the full duration of the injury.
The continuation of the Parkland formula involves a further 24 hours of fluid resuscitation again based upon Hartmann’s solution with 2ml/%TBSA/kg plus 0.5ml/%TBSA/kg of colloid.
ANAESTHETIC CONSIDERATIONS.
Initial care requires attention to detail in terms of pre-operative assessment of the patient. Both the history and events following the injury and the patients' personal history are important. The priorities are to maintain safety for the individual undergoing treatment, while maintaining an eye to the future, protecting vascular access and making appropriate airway care decisions.
The interaction of anaesthetic agents with the patient's physiology changes over time. At initial presentation for early excision and grafting, the anaesthetist may be faced with a patient who is undergoing resuscitation but remains hypovolaemic; their airway may be compromised by the oedema of both burn and crystalloid resuscitation (or is becoming so); their vascular access may be compromised by the burn itself and there may be significant problems with the acute pain of the injury. During the chronic phase of burns management, when reconstructive procedures are performed – altered pharmacokinetics, drug tolerance and extremely difficult airways are the main considerations.
Monitoring and IV access: Often IV access is still in place from the initial resuscitation. Large bore IV lies are mandatory to allow for massive fluid replacement. The cannulation site depends on the availability of unburned areas. If all appropriate sites are burned, the line may have to be placed through the burn wound after the area has been prepared in a sterile fashion. In massive burns, ECG electrodes may have to be placed directly on debrided tissue. Central venous pressure linesare useful, both for monitoring central volume and as central access for drug infusions.
Airway: Obtaining an adequate mask fit may be difficult because of oedema in the early phases of burn injury or because of scars and contractures later on. These same processes can render the trachea in burn patients extremely difficult to intubate.
Muscle relaxants: Succinylcholine is absolutely contraindicated 24 hours to 2 years after major burns, since it can produce profound hyperkalaemia and cardiac arrest.
This can develop as cholinergic sensitive ion channels migrate and increase in muscle beyond the motor end plate. Similar considerations apply to any ICU patient who is denervated, immobilised, or has had repeated sepsis. Suxamethonium can be used for rapid sequence induction early on provided it is thought essential. The same proliferation of binding sites with changes in metabolism, increase the requirement for non-depolarising agents for a given duration of effect for many months after injury.
Non-depolarising relaxantsare used when muscle relaxation is required. Burn patients show a “resistance” to these drugs (diminished response to conventional doses), in some cases requiring three-to-fivefold higher doses than non-burned patients.
Analgesics: There is no single preferred agent or combination of agents. These patients may have greatly increased narcotic requirementsbecause of tolerance and increases in the apparent volume of distribution for drugs. It is important to provide adequate analgesia. Ketamine is very useful for pain management and anaesthesia.
Temperature regulation. The most comfortable body temperature for a burn patient is about 38°C. In the burn unit patients are cared for in warmed, humidified environment. Every effort should be made to maintain normothermia during transport and surgery. The operating room, IV fluids, and blood products should be warmed, and inspired gases heated and humidified. Paediatric patients should be placed under a radiant heat source and on a warming blanket whenever possible.
Immunosuppression. The immune system is suppressed for weeks to months after burn injury, and the wound itself serves as an excellent medium for bacterial growth. Every attempt should be made to practice aseptic technique when handling patients, suctioning airways or inserting intravascular lines.
Postanaesthetic care. It is important to maintain normothermia while transporting patients back to the burns unit, since shivering could contribute to graft loss. Supplemental oxygen should be given until patients are fully recovered from anaesthesia.
Abdominal Surgery.
Anaesthesia for Abdominal Surgery
Preoperative Assessment and Optimisation For the patient requiring emergency abdominal surgery, with few exceptions, there is time to assess properly, and to resuscitate, before induction of anaesthesia. A systematic approach is best - it avoids overlooking important matters. There are some situations where the patient must go to theatre immediately - they include severe foetal distress, uncontrollable internal haemorrhage. In these situations, history, examination, resuscitation have to be done “on the run” and with no delay. In most other situations, a short delay for resuscitation is best for the patient.
Assessment must also include a thorough review of coexisting organ dysfunction. Common coexisting disorders include renal impairment, diabetes, ischaemic heart disease and chronic obstructive airways disease. Intra-abdominal pathology can contribute to respiratory insufficiency by decreasing functional residual capacity and can potentiate reflux of gastric contents.
Assessment of preoperative fluid status is of critical importance; is of fundamental importance; surgical diseases and conditions may cause severe changes in volume status producing both hypovolemia and anaemia.
History of fluid losses
· Bleeding: gastrointestinal tract sources include ulcers, neoplasms, oesophageal varices, diverticuli, angiodysplasia, or haemorrhoids.
· Emesis or gastric drainage may lead to significant losses, particularly in patients with bowel obstruction. Quantity, quality (presence of blood), and frequency of emesis should be assessed.
· Diarrhoea from intestinal disease, infection, or cathartic bowel preparation may lead to 1 to 2 litres of extra cellular fluid loss in the immediate preoperative period.
· Sequestration of fluid either in bowel lumen from ileus or interstitium from peritonitis.
· Fever increases insensible fluid loss.
Physical signs of hypovolemia
Postural changes in vital signs (increased heart rate and decreased blood pressure) may reveal mild to moderate hypovolemia; severe hypovolemia produces tachycardia and hypotension. Dry mucous membranes, skin mottling, and decreased skin turgor and temperature indicate decreased peripheral perfusion resulting from hypovolemia.
Investigations
Investigations may be clinical or laboratory. Clinical investigations are part of physical examination, and include the “bedside forced expiratory volume”, measured with a spirometer or by listening to rapid exhalation. Laboratory analysis including haematocrit, serum osmolality, urea-creatinine ratio and electrolytes may be helpful in estimating volume deficits. Laboratory investigations should always be requested if they would help to identify a problem, which can be corrected. Once ordered, they must be checked and acted upon. Once again, they may or may not influence a clinical decision to delay the operation, or to proceed.
Of the more commonly available investigations, Haemoglobin value must be interpreted in the context of the usual Hb of the population (which may be 8-9gm/dl in some areas, 12-13gm/dl in others) as well as in the context of bleeding or dehydration. A Hb of 8gm/dl in a bleeding or dehydrated patient may really be 5gm/dl when resuscitation is complete, and vascular volume is expanded, so blood transfusion may be indicated early.
Urea and Creatinine and Electrolytes may be helpful, but should be interpreted in the context of the clinical picture, and information about whether the patient has pre-existing renal failure.
Elevation of urea and creatinine may simply indicate dehydration and poor renal blood flow, or it may indicate acute or chronic renal failure. Fluid resuscitation should proceed whatever the cause, to ensure renal blood flow is improved.
Serum sodium, potassium, chloride and bicarbonate may be “normal” or “abnormal”. The first step in the acute abdominal emergency is again expansion of intravascular volume and fluid resuscitation. If renal function can be restored, the kidneys will correct the electrolyte disturbance.
Chloride and bicarbonate tend to balance each other - if one goes up the other goes down. Hypochloraemia (as in pyloric stenosis) will correct with normal saline infusion, but be made worse with Hartmann’s solution, because of the lactate, which is converted to bicarbonate. A low bicarbonate usually indicates metabolic acidosis due to poor perfusion, and corrects as the circulation improves.
Administration of bicarbonate is not often advisable, because it combines with hydrogen ions and results in formation of carbon dioxide which must be excreted by increased ventilation. Its acidosis-correcting effect is thus short-lived.
Coagulation profile must be checked to exclude coagulopathy in situations involving massive bleeding or sepsis.
Blood sugar (or urinalysis for glucose) should always be measured to allow correction in the diabetic, and to detect diabetic ketoacidosis masquerading as an abdominal emergency.
Arterial blood gases are the only accurate way of obtaining:
● PaO 2 (Oximetry is a substitute provided perfusion is good)
● PaCO 2 (End tidal CO 2 is a substitute but in the critically ill patient, there may be a wide gap between the ETCO 2 and the higher PaCO 2, not the normal 6mmHg)
● pH
● HCO 3 (which may differ from that measured with serum electrolytes)
● Identification of whether an acid-base disturbance is an acidosis or alkalosis, whether either is primarily metabolic or respiratory, and whether there is secondary compensation for the primary disturbance.
Chest X-Ray is often useful in patients with abdominal emergencies when history and examination are not clear-cut, particularly in obese patients. Look carefully for pneumothorax, haemothorax, effusion, evidence of stomach or bowel in the chest, abnormalities in the lung fields (basal atelectasis is common), size and outline of the cardiac shadow.
ECG may indicate ischaemia, atrial or ventricular enlargement, abnormalities of electrolytes (as in the peaked T waves of hyperkalaemia), arrhythmias.
Resuscitation goes hand in hand with assessment
● Airway problems such as in severe facial injury must be managed before induction of anaesthesia.
● Oxygen should always be given to the critically ill patient.
● Breathing problems such as asthma or pneumothorax must be treated before induction of anaesthesia.
● Circulation problems such as hypovolaemia or cardiac tamponade must be treated before induction of anaesthesia.
● Other emergencies, such as hyperglycaemia and electrolyte or acid-base abnormalities must have treatment commenced before induction of anaesthesia.
● Consider the need for a nasogastric tube. Decide when to insert the urinary catheter.
Resuscitation must be aggressive before and during anaesthesia. The only excuse for induction prior to resuscitation is if the patient has a condition that cannot improve without surgery. This may include massive intra-abdominal haemorrhage. Even then, resuscitation must begin before anaesthesia is induced.
Which fluids should be used in resuscitation depends on the cause of the problem, and what is available. In an adult with intra-abdominal bleeding, the choice is clearly blood and plasma expanders such as Haemaccel or Gelafusin or Dextran, supported by crystalloids - normal saline or Ringer lactate (Hartmann’s) solution. In a patient with intra-abdominal sepsis, the same approach may be needed, but blood transfusion will depend on the haemoglobin level once vascular volume has been restored. In an adult with bowel obstruction who is not shocked, saline or Hartmann’s solution may be adequate. In an infant with pyloric stenosis, saline is required initially, and Hartmann’s solution will make the hypochloraemic metabolic alkalosis worse.
Choice of Anaesthetic technique(s)
General anaesthesia is the most commonly employed technique.
Advantages
- Protection of the airway and assurance of adequate ventilation.
- Rapid induction of anaesthesia with controlled depth and duration.
Disadvantages
- Loss of airway reflexes increases risk of aspiration.
- Adverse haemodynamic consequences of general anaesthetics.
Regional anaesthetic techniques for abdominal surgery include spinal, epidural, caudal and nerve blocks. Lower abdominal procedures (e.g. inguinal hernia repair) can be performed with regional anaesthesia techniques that produce a sensory level to T4-6.
·Epidural anaesthesia is performed usually by continuous catheter technique. A “single dose” technique is applicable for surgery of less than 3 hours duration.
·Spinal anaesthesia with either single-dose or continuous-catheter technique.
·Nerve blockscan also provide adequate anaesthesia for abdominal surgery.
Bilateral blockade of T8-12 intercostal nerves provides somatic sensory anaesthesia.
Blockade of the ilioinguinal, iliohypogastric, and genito-femoral nerves produces a
field block that is satisfactory for herniorrhaphy.
Advantages
- Maintenance of a patient’s ability to communicate symptoms (i.e. chest pain).
- Maintenance of airway reflexes.
- Profound muscle relaxation and bowel contraction provide optimal surgical exposure.
- Bowel blood flow increases as a result of complete sympathectomy.
- Postoperative analgesia can be provided with continuous-catheter techniques.
Disadvantages
- Local anaesthetic toxicity with intravenous (IV) injection.
- Patient cooperation necessary for institution of block and positioning during surgery.
- Failure necessitates intraoperative conversion to general anaesthesia.
- Regional nerve blockade may be contraindicated in patients with abnormal bleeding profile or localised infection at site of injection.
- Sympathectomy produces venodilation and bradycardia; these can precipitate profound hypotension. Unopposed parasympathetic activity causes the bowel to contract and may make construction of bowel anastomoses more difficult; this can be reversed with glycopyrrolate, 0.2 to 0.4mg IV.
- High-level thoracic blocks may compromise pulmonary function.
Combined techniqueuses an epidural anaesthetic along with a light general anaesthetic. This technique is commonly employed for extensive upper abdominal surgeries.
Advantages
- Epidural anaesthesia reduces the requirement for general anaesthesia; this minimises myocardial depression and may decrease emergence time and nausea.
- Combined techniques are particularly useful in reducing post-operative ventilatory depression and improving pulmonary function early after upper abdominal surgery.
Monitoring
The most important monitoring of the patient is clinical including pulse, blood pressure, colour, respiration in addition to monitoring the surgical field, blood loss, urine output and fluid input. Heart sounds are useful to monitor particularly in children.
The next important set of instrument monitors are pulse oximetry, end tidal CO2 monitoring, ECG and temperature.
If available, CVP monitoring may be a useful guide, particularly in the patient who you think has had adequate fluid/blood replacement, but who remains hypotensive. Supported by a high CVP reading, this may be an indication for adrenaline infusion rather than more fluid, provided all other causes of hypotension have been looked for (e.g. pneumothorax, excess anaesthetic agent).
Other forms of monitoring in the critically ill patient might include an arterial line for BP and blood gas sampling, and occasionally a pulmonary artery catheter, which may show that despite a high CVP, the left atrial pressure, as reflected by the pulmonary capillary wedge pressure, is low.
Neuromuscular function monitoring is helpful in those patients who do not breathe well after reversal of muscle relaxants.
In situations where they are available, monitoring of inspired and expired oxygen, nitrous oxide and volatile agent should be used. Airway pressure, tidal and minute volume measurements likewise should be used if available.
Management of Anaesthesia
Induction of Anaesthesia.Restoration of volume deficits before induction and careful titration of sedative premedications provide more haemodynamic stability.
Rapid-sequence inductionis required for all patients considered to have full stomachs.
Indications include:
a. Trauma; gastric emptying is delayed.
b. Bowel obstruction and ileus.
c. Symptomatic hiatal hernias.
d. Second or third trimester of pregnancy.
e. Significant obesity.
f. Ascites.
Maintenance of Anaesthesia
Maintenance of anaesthesia may be achieved with nitrous oxide, oxygen and a volatile agent. If there is no nitrous oxide or it is contra-indicated, an air/oxygen mixture and volatile agent can be used. If there is no oxygen, just air and volatile agent, bearing in mind that the amount of the anaesthetic agent required will be higher than if it is used with nitrous oxide. If there is no air, oxygen and volatile agent can be used.
The maintenance phase requires observation and monitoring of the patient, and of the surgery, with particular attention to fluid and blood loss. If major surgery is proposed, or if the patient was dehydrated or hypovolaemic, measurement of urine output is a good guide to renal perfusion.
Fluid management requires administration of maintenance fluids and replacement of both deficits and ongoing losses.
1. Bleeding should be estimated both by direct observation of the surgical field and suction traps and by weighing sponges. Blood loss concealed beneath drapes or within the patient may be impossible to estimate.
2. Bowel and mesenteric oedema can result from surgical manipulation or intestinal tract disease.
3. Evaporative losses from peritoneal surfaces are directly related to the area exposed. Fluid replacement is guided by clinical judgment or invasive monitoring; as a rough estimate, 10 to 15 ml/kg per hour may be required.
4. Abrupt drainage of ascitic fluid with surgical entry into the peritoneum can produce acute hypotension from sudden decreases of intra-abdominal pressure and pooling of blood in mesenteric vessels. Postoperative reaccumulation of ascitic fluid can produce significant fluid losses.
5. Nasogastric and other enteric lossshould be quantified and replaced appropriately.
Muscle relaxationis required for all but the most superficial intraperitoneal operations; sufficient relaxation is critical at abdominal closure, since bowel distention, oedema, or organ transplantation increase the volume of abdominal contents. A non-depolarising muscle relaxant and intermittent positive pressure ventilation allows the best conditions for the surgeon. If there are no relaxants, controlled or assisted ventilation will still assist the surgeon.
Use of nitrous oxide(N20) may cause bowel distention. Because N20 is more soluble than nitrogen, it diffuses into bowel lumen faster than nitrogen can diffuse out; intraluminal gas volume doubles in approximately 10 minutes when 60% N20 is inspired. Distention can make closure difficult, and increased intraluminal pressures may cause impaired perfusion of obstructed bowel. The use of N20 is relatively contraindicated in closed-loop bowel obstructions or during construction of anastomoses in unprepared bowel.
NG tubesare frequently placed in the perioperative period. Preoperative placementis indicated for decompression of the stomach, especially in trauma victims or patients with obstructed bowel. Although suction via a large-bore NG tube can reduce the volume of gastric air and contents, it does not eliminate these entirely. NG tubes may compromise mask fit and provides a route for reflux of gastric contents past the lower esophageal sphincter. Before induction, suction should be applied to NG tubes; during induction, tubes should be allowed to drain. Cricoid pressure may prevent reflex when a NG tube is present. Intraoperative placementis required to drain gastric fluid and air during abdominal surgery.
NG and orogastric tubes should never be placed with excessive force; lubrication and head flexion facilitate insertion. Tubes can be directed into the esophagus using a finger in the oropharynx or with McGill forceps under direct visualisation with a laryngoscope. If these methods fail, a large, split endotracheal tube (9.5cm or larger) can be used as an introducer: the split endotracheal tube is introduced orally into the esophagus and the NG tube passed through the lubricated lumen of the tube into the stomach; the split tube is then removed while stabilising the NG tube.
Complicationsof NG tube insertion include bleeding, submucosal dissection in the
retropharynx, or placement in the trachea. Intra-cranial placement has been described in patients with basal skull fracture. The NG tube should be secured carefully to avoid excessive pressure on the nasal septum or nares, which may cause ischaemic necrosis.
Common Intraoperative problemsassociated with abdominal surgery include the following:
a. Pulmonary compromise,often caused by retraction of abdominal viscera to improve surgical exposure (insertion of soft packs or rigid retractors), insufflation of gas during laparoscopy, or Trendelenberg positioning. These maneuvers may elevate the diaphragm, decrease FRC, and produce hypoxaemia. Application of positive end-expiratory pressure (PEEP) may counter these effects.
b. Temperature control.Heat loss in open abdominal procedures is common.
c. Haemodynamic changes as a result of bowel manipulation(i.e. hypotension, tachycardia and facial flushing).
d. Opioids may aggravate biliary tract spasm.Although uncommon, opioids may produce painful biliary spasm in some patients when administered as a premedication or epidurally. Spasm can be reversed with naloxone; nitroglycerin and glucagon also relieve spasm by nonspecific smooth muscle relaxation.
e. Faecal contaminationoccurs from perforation of the gastrointestinal trace. Infection and sepsis can progress rapidly.
f. Hiccupsare episodic diaphragmatic spasms that may occur spontaneously or in response to stimulation of the diaphragm or abdominal viscera. Potential therapies include:
- increasing depth of anaesthesia to ameliorate the reaction to endotracheal, visceral, or diaphragmatic stimulation.
- Removal of the source of diaphragmatic irritation, such as gastric distention.
- Increasing the degree of neuromuscular blockade may decrease the strength of spasms.
Complete diaphragmatic paralysis is difficult to achieve and may be possible only with doses of relaxants in excess of those required for relaxation of abdominal musculature.
- Chlorpromazine, rarely used intraoperatively, can be titrated in 5-mg IV increments.
Anaesthetic considerations for specific abdominal procedures
Gastric surgery is usually performed with general anaesthesia or combined general anaesthesia and epidural block. The high likelihood of aspiration in these patients necessitates a rapid sequence or awake intubation. Large third-space losses and potential for hemorrhage should be anticipated.
Gastrostomy can be performed through a small, upper-abdominal incision or percutaneously with an endoscope. Local anaesthesia with sedation is often adequate in the debilitated elderly patient, although some patients require general anaesthesia.
Intestinal and peritoneal surgery. Indications for small bowel resectioninclude penetrating trauma, Crohn’s disease, obstructing adhesions, Meckels diverticulum, carcinoma, or infarction (from volvulous, intussusception, or thromboemboli). Patients are usually hypovolaemic and are at risk for having a full stomach.
Appendectomyis performed through a small lower-abdominal incision. Fever, poor oral intake, and vomiting may produce hypovolaemia; IV hydration before induction is indicated. In rare cases when sepsis and dehydration are absent, a regional anaesthetic may be appropriate; otherwise, general anaesthesia with rapid-sequence or awake intubation is necessary.
Colectomy or hemicolectomyis used to treat colon cancer, diverticular disease, Crohn’s disease, ulcerative colitis, trauma, ischaemic colitis, and abscess. Emergency colectomy on unprepared bowel carries a high risk of peritonitis from fecal contamination. Some emergencies involving the colon are treated with an initial diverting colostomy followed later by bowel preparation and elective colectomy. Patients must be evaluated for hypovolaemia, anaemia, and sepsis. All emergency colectomies and colostomies should be treated as if at risk for full stomach. Combination general and regional anaesthetics are preferable.
Perirectal abscess drainage, haemorrhoidectomy, and pilonidal cystectomyare relatively noninvasive and brief procedures. Pilonidal cysts are usually excised with the patient in the prone position; abscess drainage and haemorrhoidectomy can be performed with the patient either prone or in lithotomy position. If general anaesthesia is employed, deep planes of anaesthesia or use of muscle relaxants may be necessary to achieve adequate sphincter relaxation.
Intubation is required to provide general anaesthesia for prone patients. Hyperbaric spinal anaesthesia is used for procedures in lithotomy position, while hypobaric spinal is useful for the flexed prone (jackknife) or knee-chest position; caudal block is applicable with either position.
Inguinal, femoral, or ventral herniorrhaphiescan be performed with the patient under local anaesthesia, regional anaesthesia, (spinal, epidural, caudal, or nerve block), or general anaesthesia. Maximum stimulation and a profound vagal response may occur during spermatic cord or peritoneal retraction. If general anaesthesia is selected, either a mask technique (e.g. laryngeal mask airway) or deep extubation should be considered to decrease coughing on emergence, which can strain the hernia repair.
Biliary tract procedures. Cholecystectomyis a common procedure performed either as open laparotomy or by laparoscopic technique. General anaesthesia is required for either technique.
Postoperative Care
Care in the Recovery Room must equal that during anaesthesia until the patient is capable of looking after his/her own airway and breathing and is fully conscious. The patient in Recovery should continue to receive oxygen, have continuous monitoring of airway, breathing and circulation, and be given analgesia as required. The critically ill and any unstable patients should be considered for admission to a high dependency unit 24-48 hrs.
The anaesthetist is often the best resource a surgeon has for advise on post-operative problems such as pain, management of nausea and vomiting, fluid and electrolyte replacement.
SELF-ASSESSMENT QUESTIONS
- List five components of the primary survey.
- Describe the expected signs and symptoms in a patient who has lost the following percentage of their blood volume: 10%, 20%, 30% and 40%.
- What are the aims of resuscitation in the burn patient?
- How is the surface area of a burn estimated in adults and children?
- What are the factors, which increase the risk of regurgitation and aspiration ogf grastric contents?
Define “massive transfusion”. What are the physiological effects of massive transfusion? How would you manage massive transfusion?
TRAUMA, BURNS AND ABDOMINAL SURGERY CASE STUDIES
Case No 14.1
Tunga is a 29 year old lady who weighs 130 kg. She has been admitted for a cholecystectomy.
Describe the problems associated with obesity and anaesthesia.
How would you modify your technique for her obesity?
Discuss the potential complications of upper abdominal surgery for this patient.
What are the options for post-operative pain relief?
What are the physiological changes, which occur when a patient is positioned head down?
The surgery proceeds uneventfully and you reverse the patient and extubate her when you consider she is able to maintain her own airway. You receive a call from the recovery room 20 minutes later because the lady is un-rousable and having difficulty maintaining oxygen saturations above 90%.
Discuss the possible aetiology.
Describe your management.
Case No 14.2
Tulga has been admitted to hospital following a GI bleed. Tulga is a 40-year-old Mongolian male who admits to frequent vodka drinking. His oxygen saturation in air is 91% and increases to 93% when breathing O2 at 6lpm via a face-mask. He is jaundiced and has been commenced diuretics for ascites. The surgeons are planning on taking him to theatre for a laparotomy.
Discuss the possible causes for his jaundice.
What are the implications for anaesthesia and surgery?
How will you reduce the risk of aspiration?
Case No 14.3
Ganbold is found unconscious in his ger. He has suffered significant burns
What clinical features are most important for deciding his immediate and early management?
Discuss fluid management for burns victims.