Comparison of thiopentone and midazolam for induction of anaesthesia: influence of diazepam premedication.

Forty-eight healthy patients undergoing routine surgery participated in this double-blind parallel study in which thiopentone sodium and midazolam maleate were compared for induction of anaesthesia. Twelve patients in each group received diazepam premedication. The purpose of this study was three fold; first to compare the efficacy of these two drugs as induction agents using fixed criteria, second to find the optimal dose of midazolam for induction and, finally, to evaluate the effects of diazepam premedication on the induction dose of both drugs. The results showed that adequate induction of anaesthesia was achieved using 0.30 milligrams per kilogram of midazolam and 3.99 milligrams per kilogram of thiopentone. These doses were not altered by pre-operative medication with diazepam. The recovery time was significantly prolonged in those patients who had received midazolam. The shortest recovery time was observed in those patients who had received thiopentone with diazepam. There were four cases of phlebitis in the thiopentone group and two in the midazolam group. In conclusion, midazolam maleate, which is a water soluble benzodiazepine, provided satisfactory induction of anaesthesia at a dose of 0.30 milligrams per kilogram. However, recovery time was significantly prolonged in patients who received midazolam.