Rapid inhalation induction with isoflurane in humidified carrier gas

This study was designed to determine if rapid inhalation induction of anaesthesia (RII) with 5% isoflurane (4.5 MAC equivalent) in oxygen offers any advantage in terms of complication rate, speed of induction and patient acceptance in comparison with a previously described technique of RII using 2% isoflurane in nitrous oxide and oxygen. Forty ASA I and II unpremedicated patients were allocated randomly to receive RII with either 5% isoflurane in oxygen or 2% isoflurane and nitrous oxide in oxygen. The carrier gas was humidified in order to limit airway irritation associated with the use of isoflurane for inhalation induction. In this study the observed difference in mean induction time (7 s) between the two groups was neither clinically nor statistically significant. The groups were similar also with regard to complication rate and patient acceptance.