Halothane, enflurane, sevoflurane, and isoflurane are anesthetic agents that have bronchodilating properties. Sevoflurane is the least irritating to the airways in awake patients, but its bronchodilating properties are weaker than those of the other agents. Halothane is the next least irritating to inhale and has the most potent bronchodilating properties of all the agents. It has been used from subanesthetic concentrations (0.25 per cent) to anesthetic concentrations (1.25 per cent), and has been beneficial in this group of patients who are unresponsive to conventional therapy.
Halothane can cause serious ventricular arrhythmias, particularly in the presence of high levels of circulating catecholamines. Side-effects include hypotension, bradycardia, and rarely hepatitis. If halothane is used for prolonged periods, accumulation of its metabolites can occur and this should be monitored.
It is imperative that inhalational anesthetics are administered by a clinician who has experience of using these agents and that appropriate cardiorespiratory support and resuscitation facilities are available.
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