8. RESPIRATORY DISEASE

Respiratory disease often occurs in patients presenting for anaesthesia and surgery. Common respiratory diseases include asthma, chonic obstructive lung disease, upper respiratory tract infections, tuberculosis and smoking. General anaesthesia will have several effects on the patient’s respiratory function including a decrease in lung volume and a decreased respiratory rate response to hypoxia and hypercarbia. Respiratory function will be further decreased by poorly treated postoperative pain.

Preoperative Assessment

The anaesthetist must take a full history, examination and order relevant investigations.

Respiratory function testing is useful in predicting which patients may not survive a pneumonectomy but is less reliable in predicting postoperative pulmonary complications for other surgical procedures. The anaesthetist may need to rely on clinical findings.

The history and examination may reveal important information and conditions which are significant risk factors including dyspnoea, cough and sputum production, recent chest infection, haemoptysis, wheezing, smoking, obesity and pulmonary complications from previous surgery.

An increase in the patient’s respiratory rate, especially above 25 breaths each minute, is associated with an increase in postoperative pulmonary complications.

Bacterial and even viral respiratory infections will have an adverse effect on respiratory function, increasing airflow obstruction for up to 5 weeks after the infection.

Wheezing is usually reversible and should be treated with bronchodilators however the anaesthetist must also check and treat for non-respiratory causes of wheezing such as cardiac failure.

Smoking should be ceased.

Patients who are not short of breath at rest and who can climb more than two flights of stairs are unlikely to develop postoperative pulmonary complications.

The anaesthetist must treat any potentially reversible respiratory disease before surgery. They should encourage the patient to stop smoking, treat acute bacterial infections, humidify inhaled gases, encourage chest physiotherapy and treat bronchospasm and right heart failure.

Respiratory Infections

90% of upper respiratory tract infections are likely to be viral. If bacterial infection is suspected the patient should be treated with antibiotics prior to surgery. Even viral infections will increase the risk of laryngospasm and bronchospasm and it is wise to delay surgery if possible for 5 weeks.

A careful history and examination looking for fever, cough, shortness of breath and lethargy will allow the anaesthetist to assess the severity of the infection.

Tuberculosis

Tuberculosis increases the risk to the patient and medical staff. Early pulmonary tuberculosis may be asymptomatic. Cough, haemoptysis, chest pain and shortness of breath occur late in the disease.

Patients with tuberculosis must have a careful history and examination taken.

The anaesthetist must also be aware of non-pulmonary symptoms. Tuberculosis can affect many organs including the central nervous system, kidney and bone marrow. Hyponatraemia may occur with pulmonary tuberculosis. If time allows, active tuberculosis must be treated before any surgery.

Asthma

A careful history, examination and simple investigations will allow the anaesthetist to determine how severe a patient’s asthma usually is and if the patient’s asthma could be improved before surgery.

As with all anaesthetics, the urgency of the surgery needs to be balanced against the severity of a patient’s disease.

To establish how severe a patient’s asthma usually is, the anaesthetist needs to know how often the patient has asthma attacks, what medication they are taking, how often they take the medication and what their best exercise tolerance is.

If the patient’s asthma is currently worse than usual they should be treated prior to surgery with increased bronchodilators and/or a course of oral steroids.

All asthmatics may benefit from nebulised salbutamol immediately before anaesthesia.

The anaesthetist should avoid histamine-releasing drugs and if possible avoid endotracheal intubation, which can precipitate bronchospasm.

Chonic Obstructive Pulmonary Disease (COPD)

Chonic obstructive pulmonary disease increases the risk of hypoxaemia, hypercarbia, bronchospasm and postoperative pulmonary complications. The anaesthetist should ask about cough, sputum production, shortness of breath, exercise tolerance, smoking and recent chest infections.

The chest X-ray may be normal in early disease.

The patient should stop smoking and be treated for any chest infections. These patients may have some reversible lung disease and may benefit from preoperative bronchodilators, steroids, antibiotics and chest physiotherapy.

Postoperative pain control is very important in any patient with respiratory disease.