RAPID INDUCTION OF HALOTHANE ANAESTHESIA IN MAN

The cardiopulmonary and anaesthetic responses of nine healthyvolunteers, breathing concentrations of 1-4% halothane in oxygen,were studied. Supine fasting subjects breathing room air exhaledto residual volume and then inhaled a vital capacity breathof 1, 2, 3 or 4% halothane in oxygen. After a breath-hold of30–90 s they exhaled and then breathed spontaneously thesame anaesthetic mixture for up to 2 min. The electrocardiogram,arterial pressure, heart sounds and arterial oxygen saturation,were monitored, and respiratory gases were analysed by massspectrometry. The maximum effect was seen after breathing 4%halothane. All volunteers were amnesic after the first breathand unresponsive to command after 2 min. Little or no excitementoccurred. A maximum decrease of 12 mm Hg in systolic pressurewas seen while breathing 4% halothane. Bradycardia, hypoxiaand clinically important hypercarbia did not occur. At all inspiredconcentrations of halothane, the end-tidal halothane concentrationincreased rapidly and was 30% of the inspired value after 1min. No volunteer found this technique to be unpleasant. Rapidinduction of general anaesthesia with 2–4 % halothanein oxygen is effective, safe and well accepted by healthy youngadults.