14. EMERGENCY SURGERY

Patients for emergency surgery are at a high risk of perioperative complications. The anaesthetist must carefully assess the patient by history, examination and investigations in the time available before surgery is required. The anaesthetist must try to resuscitate (airway management, ventilation and intravenous fluid) the patient before surgery but for extreme emergencies they may need to resuscitate and anaesthetise at the same time.

The anaesthetist must balance the urgency of the surgery and the need for preoperative assessment and treatment.

Risk

The anaesthetist must be aware of problems related to inadequate preparation of the patient. The patient may not be starved and therefore at risk of aspiration. These patients require a rapid sequence induction.

Coexisting medical problems such as diabetes, asthma and ischaemic heart disease may be poorly treated. There may not be enough time to properly investigate the patient and order blood cross matching.

Patients for emergency surgery often have severe changes in their health that must be assessed and if time allows, treated before surgery. Some examples include severe dehydration with severe electrolyte changes due to intestinal obstruction and vomiting/diarrhoea, severe hypovolaemia and anaemia from haemorrhage. There may be septic shock from untreated infections or there may be a damaged/obstructed airway in the trauma patient.

Choice of Anaesthesia

The choice of anaesthesia will depend on the type of surgery, the experience of the anaesthetist, the equipment available, the time available and the condition of the patient. Hypovolaemia and a full stomach are two common but deadly problems in emergency anaesthesia that the anaesthetist must be aware of when they plan the type of anaesthesia.

If appropriate to the surgery required, regional anaesthesia of a limb or local anaesthesia may be the safest choice of anaesthesia. Spinal/epidural anaesthesia will reduce the risk of aspiration, however, hypovolaemia must always be corrected before spinal/epidural anaesthesia. These emergency patients must have a normal blood pressure and no tachycardia. There should be no postural drop in blood pressure and adequate urine output.

The anaesthetist must ensure that a patient with burns has been given enough intravenous fluid. A burnt patient will need at least 4ml/kg times the percentage of body burnt, in the first 24 hours to replace fluid loss. For example, a 70 kg man with 30 percent burns will need at least (70 x 4 x 30) 8.4 litres in the first 24 hours. Usually half of the calculated fluid loss is given over the first 8 hours and the remainder over the next 16 hours. The patient will also need their daily maintenance fluid.

General anaesthesia may be safer for patients with untreated hypovolaemia but they should receive reduced doses of almost all anaesthetic drugs except muscle relaxants.

Induction agents especially need to be given very carefully as these may cause cardiovascular collapse from vasodilatation in the hypovolaemic patient. If general anaesthesia is chosen then the anaesthetist must prevent aspiration of gastric contents. The non-fasted patient must have a rapid sequence induction and intubation of the trachea.

The anaesthetist should choose the type of anaesthetic depending on his or her experience and training, their assessment of the patient, the equipment and drugs available and the needs of the surgeon. The anaesthetist must try to treat patient problems caused by the emergency and other medical problems before giving an anaesthetic if time allows.