Vital capacity rapid inhalation induction technique: comparison of sevoflurane and halothane

Induction of anaesthesia using the vital capacity rapid inhalation induction (VCRII) technique with either sevoflurane or halothane was compared. The induction time, characteristics, and acceptability were assessed. Thirty-two volunteers were given one of the vapours: 17 received sevoflurane and 15 halothane. Subjects were unpremedicated and breathed approximately 2.6 x minimum alveolar concentration (MAC) equivalent of either agent. There were no differences in the patients' cardiovascular or respiratory variables. The mean time for induction of anaesthesia with halothane (153 +/- 46 sec, SD) was slower than with sevoflurane (81 +/- 22 sec, SD, P < 0.05), reflecting its higher blood:gas solubility. There were fewer induction complications such as coughing and movement in the sevoflurane than in the halothane group. Subjects in the sevoflurane group found the smell of anaesthetic more acceptable than those in the halothane group (65% vs 13%, respectively). Subjects in both groups had no objection to undergoing the procedure again. It is concluded that both halothane and sevoflurane are effective in VCRII of anaesthesia without premedication. However, the slower speed of induction with halothane frustrated the anaesthetist because of the longer induction time, and may increase the chance of pronounced excitatory phenomena occurring.