Keep the breathing, stop the wheezing

Jean François Brichant - Department of Anaesthesia & Intensive Care Medicine
CHR de la Citadelle, Liege University Hospital, Belgium

Perioperative bronchospasm is an anaesthetic emergency that can be life threatening. Although in recent years much emphasis has been directed towards prevention, acute increases in airway resistance are still not uncommon.

Patient at highest risk include those with asthma, chronic obstructive pulmonary disease (COPD) and heavy smokers. However, most patients with a history of asthma may safely undergo anaesthesia, provided that adequate techniques are used (20). Most bronchospastic episodes occur in patients who have no history of hyperactive airways (4). In the ASA closed claims study, bronchospasm was the damaging event in 2% of the data base and 70% of these were for death (4). Thus, bronchospasm may occasionally lead to severe adverse outcome.

Although recognition of bronchospasm can be difficult in anaesthetized patients, prompt diagnosis and treatment are essential for favourable outcome. Bronchospasm usually manifests during anaesthesia as expiratory wheezing, desaturation, increased circuit pressure, prolonged expiration, altered capnogram and reduction in tidal volumes. The chest may also be silent on auscultation in case of severe bronchospasm.

Most often, bronchospasm results from non-specific bronchial hyperresponsiveness, but occasionally, it is the consequence of anaphylactoid or allergic reaction. Generally, it is cholinergically mediated (2).

A variety of preanaesthetic measures can reduce the risk of perioperative bronchospasm. They include the administration of β-adrenergic agonists, anticholinergics and/or steroids. Preinduction administration of inhaled β-adrenergic agonists and/or muscarinic antagonists is the mainstay of peri-anaesthesia bronchoconstriction prevention (10). Patients with moderate to severe asthma and having used steroids in the past may benefit from the administration of steroids a few hours before anaesthesia (13,17). When feasible, a steroid course administered in the week before anaesthesia might be beneficial in patients with ongoing wheezing. Although theophylline is sometimes used in the treatment of chronic asthma to prevent acute episodes of bronchospasm, it should not be used acutely in the perianaesthesia setting as it has a very poor therapeutic/toxic index.

Because instrumentation of the airways is a frequent trigger of bronchospasm, avoiding tracheal intubation seems important for patients with hyperactive airways. Therefore, laryngeal mask airway (LMA) or regional anaesthesia should be used whenever possible in these patients (11,18).

Concerns about sympathetic blockade induced by high neuraxial block and leading to bronchospasm are unfounded (7). Also, most patients with hyperactive airway will stand pulmonary function changes induced by regional anaesthesia (9). This, however, could be a concern in some patients with COPD or current upper respiratory infection as ability to cough could be reduced.

When inducing general anaesthesia, propofol or ketamine should be used to reduce the risk of bronchospasm and barbiturates must be avoided (3,5,14). Propofol preparations containing sulfate may be less effective than those using EDTA in preventing bronchospasm (15). Intravenous administration of lidocaine a few minutes before induction attenuates reflex bronchoconstriction (8).

Most volatile anaesthetics are effective bronchodilators (1,19). Sevoflurane is as effective as halothane and more potent than isoflurane (16). Desflurane has not been shown to have the bronchodilating effects of other volatile anaesthetics (6).

Regarding muscle relaxants, rapacuronium administration has been associated with numerous cases of bronchospasm and was therefore withdrawn from the market. Mivacurium must not be used in patients with a history of COPD or asthma as its administration is associated with histamine release.

When bronchospasm is suspected in the perioperative period, the first step in managing the patient is to confirm the diagnosis as several other conditions can mimic bronchospasm. They include pulmonary oedema, tension pneumothorax, aspiration of gastric contents, oesophageal intubation. Next, the noxious stimuli should be stopped and the patient ventilated adequately to maintain inspiratory flow. Anaesthesia should be deepened with a volatile agent such as sevoflurane or with ketamine or propofol. β2-agonists with rapid onset of action should also be administered. The inhalational route is as effective as parenteral therapy and is associated with fewer side-effects. Numerous puffs should be administered via a spacer in intubated and mechanically ventilated patients (12). Intravenous lidocaine might also be useful whereas atropine has not proven to be effective in that setting (8).

Finally, it is worth pointing out that a full explanation of the event should be given to the patient, that the problem must be documented in the anaesthesia record and that the patient must be given a letter warning future anaesthetists.

References

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