RAPID INDUCTION OF HALOTHANE ANAESTHESIA IN MAN

Abstract

The cardiopulmonary and anaesthetic responses of nine healthy volunteers, breathing concentrations of 1-4% halothane in oxygen, were studied. Supine fasting subjects breathing room air exhaled to residual volume and then inhaled a vital capacity breath of 1, 2, 3 or 4% halothane in oxygen. After a breath-hold of 30-90 s they exhaled and then breathed spontaneously the same 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 mass spectrometry. The maximum effect was seen after breathing 4% halothane. All volunteers were amnesic after the first breath and unresponsive to command after 2 min. Little or no excitement occurred. A maximum decrease of 12 mm Hg in systolic pressure was seen while breathing 4% halothane. Bradycardia, hypoxia and clinically important hypercarbia did not occur. At all inspired concentrations of halothane, the end-tidal halothane concentration increased rapidly and was 30% of the inspired value after 1 min. No volunteer found this technique to be unpleasant. Rapid induction of general anaesthesia with 2-4% halothane in oxygen is effective, safe and well accepted by healthy young adults.