Anaesthesia in asthmatic patients

Overview

Patients with asthma are at increased risk of perioperative respiratory complications. Careful preoperative optimization, avoidance of triggers, and appropriate anaesthetic selection are essential to reduce morbidity.

Perioperative considerations

Risk of respiratory complications

Patients are at risk of:

• Bronchospasm

• Mucous plugging

• Pneumothorax

• Atelectasis

• Pneumonia

Also consider the possibility of:

• Pulmonary hypertension

• Right ventricular failure

Preoperative optimization

Optimize respiratory status before surgery by treating:

• Bronchospasm

• Respiratory infection

• Atelectasis

Avoid triggers and exacerbating factors

Where possible:

• Avoid general anaesthesia.

• Avoid endotracheal intubation.

• Avoid histamine-releasing medications.

• Avoid light anaesthesia.

Medication management

• Continue the patient's usual inhaled medications throughout the perioperative period.

• Administer stress-dose corticosteroids (steroid cover) in patients with recent high-dose corticosteroid use.

Management of severe asthma exacerbation

Refer to the Asthma section for the management of severe asthma exacerbations.

Anaesthetic agents

Preferred induction agents include:

• Ketamine (IV): preferred because of its bronchodilator effect.

OR

• Propofol (IV): has bronchodilator properties.

For inhalational anaesthesia:

• All volatile anaesthetic agents have bronchodilator effects.

• Sevoflurane is generally the preferred volatile agent.

Airway and ventilatory management

Consider non-invasive positive pressure ventilation (NIPPV) as a rescue measure before proceeding to endotracheal intubation.

If intubation and mechanical ventilation are required:

• Use permissive hypercapnia.

• Use a low respiratory rate, initially 10–12 breaths/minute, with further reduction if necessary.

• Allow a prolonged expiratory time using an inspiratory-to-expiratory (I:E) ratio of 1:3, 1:4, or 1:5.

• Use a tidal volume of 6–8 mL/kg.

• Adjust FiO₂ to maintain PaO₂ >60 mmHg.