Preoperative Preparation

General assessment

This involves history, examination and investigation.

History. Ask about symptoms of wheeze, cough, sputum production, haemoptysis, chest pain, exercise tolerance, orthopnoea and paroxysmal nocturnal dypsnoea. The diagnosis of chronic chest complaints such as asthma or bronchiectasis is often known. Present medication and allergies are noted, and a history of smoking sought. Previous anaesthetic records may be available and can help in planning care.

Examination. Inspect for cyanosis, dyspnoea, respiratory rate, asymmetry of chest wall movement, scars, cough and sputum colour. Percussion and auscultation of chest may suggest areas of collapse and consolidation, pleural effusions, pulmonary oedema or infection. Cor pulmonale may be evident as peripheral oedema and raised jugular venous pressure. A bounding pulse and hand flap may indicate carbon dioxide retention, and enlarged lymph nodes in the neck may suggest lung cancer.

Investigations. Leucocytosis may indicate active infection, and polycythaemia chronic hypoxaemia. Arterial blood gases should be performed in patients who are dyspnoeic with minimal exertion and the results interpreted in relation to the inspired oxygen concentration. Preoperative hypoxia or carbon dioxide retention indicates the possibility of postoperative respiratory failure which may require a period of assisted ventilation on the Intensive Care Unit.

Pulmonary function tests, if available, provide baseline pre-operative measurements. The chest clinic will have charts to compare these results against those predicted for the patients age, sex and weight. The results are also compared against the patient's previous records to assess current disease control.

• FEV1.0 (Forced Expiratory Volume in 1 second) and FVC (Forced Vital Capacity) are commonly measured. A reduction in the FEV1.0:FVC ratio indicates obstructive airways disease. (The normal is 0.75 (75%) or more). A reduction in FVC occurs in restrictive lung disease.
• An FEV1.0 or FVC less than 70% of predicted, or an FEV1.0:FVC ratio less than 65%, is associated with an increased risk of pulmonary complications.

Chest X-rays may confirm effusions, collapse and consolidation, active infection, pulmonary oedema, or the hyperinflated lung fields of emphysema.

An electrocardiogram may indicate P-pulmonale, a right ventricular strain pattern (dominant R waves in the septal leads) or right bundle branch block.

Pre-medication

In patients with poor respiratory function premedication (if used) must not cause respiratory depression. Opiates and benzodiazepines can both do this, and are best avoided if possible, or used with caution. Humidified oxygen may be administered (see Oxygen therapy section).

Anticholinergic drugs (e.g. atropine) may dry airway secretions and may be helpful before ketamine or ether.

Specific Respiratory Problems

Coryza (common cold)

Most patients with minor upper respiratory infections but without fever or productive cough can have elective surgery. However, patients with underlying respiratory disease or those having major abdominal or thoracic surgery should be postponed.

Respiratory tract infections

Patients with fever and productive cough should be treated before undergoing elective surgery as there is an increased risk of postoperative pulmonary complications. When these patients present for emergency surgery a course of antibiotics should be administered.

Asthma

Asthma causes hyper-responsive airways with oedema, inflammation and narrowing due to smooth muscle spasm. It is characteristically reversible, unlike chronic obstructive pulmonary disease. Elective cases should not be undertaken unless asthma is well controlled, and the anaesthetist will need to be informed of poorly controlled and severe asthmatics in advance. A consultation with a respiratory physician may be useful. In poorly controlled asthma a short course of steroids is often effective in improving control of the disease. Patients on preoperative steroids will need extra perioperative supplementation if they are taking more than the equivalent of 10mg of prednisolone a day.

Preoperative assessment

• The disease is assessed by the frequency and severity of attacks, including hospital and intensive care admissions, and by drug history. The patient will be able to say how good (or bad) their asthma is. Examination may reveal expiratory wheezes, use of accessory muscles or an over-distended chest. Peak expiratory flow rates (PEFR) pre- and post-bronchodilator should be measured, although trends in PEFR are more useful (the patient may have their own PEFR records). Baseline spirometry, (FEV1.0 and FEV1.0:FVC ratio) is also helpful.
• Blood gas analysis is usually reserved for severe disease (breathlessness on minimal exertion).
• Before surgery, patients should be free of wheeze, with a PEFR greater than 80% of the predicted or personal best value. Severe asthmatics may require their inhalers being changed to nebulisers. Similarly inhaled steroid dose may have to be increased or oral steroids commenced (Prednisolone 20-40mg daily) one week prior to surgery - consult a respiratory physician early.

Perioperative management

• Consider converting inhaled beta 2 agonists such as salbutamol to the nebulised form. Give nebulised salbutamol (2.5-5.0mg) with premedication.
• Avoid aspirin or NSAIDs and any other allergens known to the patient. If applicable local or regional anaesthesia used alone will avoid the problems of general anaesthesia. However, if general anaesthesia is required, the addition of regional techniques can reduce operative volatile anaesthetic and post operative opioid requirements and the likelihood of respiratory complications.
• Ketamine and all the volatile agents are bronchodilators. Airway manipulation should be kept to a minimum and take place only under adequate anaesthesia.
• Controlled ventilation with the use of neuromuscular blocking drugs will be needed for major or long procedures. In cases with severe airways obstruction the ventilator rate may have to be sufficiently low to allow the slow expiration of asthma. Atracurium and tubocurare should be avoided as they release histamine. This is also true of morphine - pethidine is often preferred in patients who are wheezy on presentation.
• Residual neuromuscular blockade must be fully reversed, and extubation can occur when spontaneous ventilation is resumed and oxygenation is adequate.

Postoperative care

• Adequate analgesia is vital.
• Humidified oxygen is continued for up to 72 hours following major abdominal or thoracic surgery (see Oxygen therapy section), together with regular physiotherapy until the patient regains mobility.
• Maintenance of hydration with intravenous fluids is required until oral intake is sufficient.
• Usual anti-asthmatic medications are resumed immediately. This may require intravenous steroids to temporarily replace oral (see Steroid supplementation section) and nebulised bronchodilators to replace inhalers if the patient cannot take a deep breath, or pulmonary function has deteriorated after surgery.
• Failure to ensure adequate postoperative oxygenation and ventilation may require admission to an intensive care area for a period of assisted ventilation.

Chronic obstructive pulmonary disease (COPD)

The main problems are airflow obstruction (usually irreversible), mucus hypersecretion and repeated infections. The ASA grade correlates with the risk of postoperative pulmonary problems.

If reversibility is demonstrated by spirometry (i.e. an increase in FEV1.0:FVC ratio after bronchodilator), it is treated as for asthma. A trial of a week's course of systemic steroids (Prednisolone 20-40mg daily) is used if nebulisers fail to treat wheeze. Antibiotics are only used if a change in sputum colour suggests active infection. Right and left ventricular failure is treated with diuretics. Physiotherapy will clear chest secretions and the patient is encouraged to stop smoking.

Preoperative arterial blood gas estimation is required in the patient who has difficulty climbing one flight of stairs, or who has cor pulmonale. Postoperatively, these patients may need ventilating for 1-2 days on an intensive care unit following thoracic or high abdominal surgery. The best predictor of the need for postoperative ventilation is the arterial PaO2, and whether the patient is dyspnoeic at rest.

Otherwise, perioperative considerations are the same as for asthma, except that the chances of post-operative pneumonia (pyrexia, purulent sputum) are high and will require early treatment with amoxycillin, trimethoprim or clarithromycin.

Postoperatively, care is required with oxygen supplementation as some COPD patients rely on relative hypoxia for respiratory drive. (see Oxygen therapy section).

Restrictive pulmonary disease

Restrictive disease is either intrinsic, such as pulmonary fibrosis related to rheumatoid arthritis or asbestosis, or extrinsic, such as caused by kyphoscoliosis or obesity. Oxygenation may be impaired at the alveolar level and because of poor air supply to it. Steroids are the usual treatment for fibrotic disease.

Intrinsic Disease

• The anaesthetist should be alerted early. Preoperatively obtain spirometry, arterial blood gases, lung volume and gas transfer measurements, if not done in the previous 8 weeks. A reduced PaO2 indicates severe disease. The chest physician may suggest an increase in steroid dose.
• Steroid supplementation will be required over the operative period (see Steroid supplementation section).
• Postoperatively, supplemental oxygen is given to keep SpO2>92%, and respiratory infection is treated early.

Extrinsic Disease

• The restrictive deficit here leads to rapid, shallow breathing, often relying on diaphragmatic movement to be effective. This poses problems for breathing and sputum clearance postoperatively, especially following thoracic or upper abdominal incisions.
• Blood gases remain normal until disease is severe and PaCO2 rises.
• Postoperatively, vigorous physiotherapy and adequate analgesia are vital. The patient may require ICU or HDU care if postoperative hypoxia, fatigue or carbon dioxide narcosis occur.

Bronchiectasis and Cystic Fibrosis

Prior to surgery therapy is maximised using a course of intravenous antibiotics, physiotherapy, nebulised bronchodilators and an extra 5-10mg/day of oral prednisolone, if taking long term steroids. This involves discussion with the patient's chest physician. Elective surgery is postponed if respiratory symptoms are present.

Postoperatively continue intravenous antibiotics and regular physiotherapy until discharge. The chest physician should be involved in any respiratory problems, and adequate nutrition is resumed as early as possible.

Tuberculosis

The patient with active pulmonary tuberculosis may be wasted, febrile and dehydrated. Production of sputum and haemoptysis may cause segmental lung collapse and blockage of the endotracheal tube. Humidification of anaesthetic breathing systems is therefore important, and inspired oxygen concentration will have to be increased. Appropriate intravenous fluids are given to rehydrate the patient. Anaesthetic equipment must be sterilised after use to prevent cross infection of tuberculosis to other patients. 

Anaesthesia - Techniques

Perioperatively, continuous clinical observation of the patient is combined with monitoring appropriate to the case being undertaken. Hence, the patient's colour and respiratory rate and pattern is observed, and the pulse volume and rate palpated (during anaesthesia it may be easier to palpate the facial, superficial temporal or carotid artery). Monitoring involves pulse oximetry, electrocardiogram, non-invasive blood pressure recordings and, if available, end-tidal carbon dioxide measurement.

A preoperative pulse oximeter measurement of peripheral oxygen saturation in air is useful, and the perioperative inspired oxygen concentration must be sufficient to maintain this. Those patients at greatest risk of perioperative pulmonary complications will benefit from regular blood gas analysis using an indwelling arterial catheter.

The technique of anaesthesia chosen is the one considered to carry the lowest risk of perioperative pulmonary complications. The following points should be considered:

• Regional anaesthesia will avoid the pulmonary complications of general anaesthesia, but its use is limited by the duration of local anaesthetic activity, and to certain areas of the body, i.e. face, eyes and limbs.
• Spinal/Epidural anaesthesia. High spinal and epidural techniques impair intercostal muscle function and result in a decrease in FRC and an increased risk of perioperative basal atelectasis and hypoxia. There is no clear evidence that these techniques result in fewer respiratory complications than after general anaesthesia, although avoiding tracheal intubation may decrease the risk of postoperative bronchospasm.
• Low spinal and epidural techniques can be used for surgery below the umbilicus and on lower limbs without pulmonary impairment. However, under general anaesthesia, this kind of surgery has a low risk of pulmonary complications. As such there is little to choose between these two techniques. When planning to use spinal or epidural anaesthesia ensure that the patient will be able to lie flat for an extended period.
• Ketamine anaesthesia maintains some of the airway and cough reflex. Ventilation is not depressed, but there is an increase in salivation such that atropine premedication is required. Without muscular relaxation and endotracheal intubation, the airway remains vulnerable to aspiration of vomited or regurgitated gastric contents. Ketamine as the sole anaesthetic agent is therefore not used in the patient with a full stomach, and is most commonly used for surgery of the face, limbs or perineum, where muscular relaxation is not required.
• Controlled ventilation. Endotracheal intubation using muscle relaxants and controlled ventilation will be necessary during head, neck and ear, nose and throat surgery. Here the airway must be secured at the beginning of surgery as access to it will be difficult when surgery has commenced. Also, the trachea is at risk of soiling from blood. Similarly, during thoracic or abdominal surgery muscle relaxation will be required to enable controlled ventilation, and endotracheal intubation will protect against tracheal aspiration of gut contents. When patients require surgery in the prone position airway access will be difficult, and endotracheal intubation and controlled ventilation will be required.
• Spontaneous ventilation employing a facemask avoids airway instrumentation, although leaves the airway unprotected. If available, the laryngeal mask does not stimulate the larynx, but does offer some protection for the trachea. This technique is only used for minor surgery of the limbs or body surface of short duration (less than 2 hours), when the patient can breath comfortably in the supine position or on their side. Prolongation of spontaneous ventilation anaesthesia may lead to respiratory depression and delayed recovery. 

(Continued ...)

---

© World Federation of Societies of Anaesthesiologists WWW implementation by the NDA Web Team, Oxford

---