Comparative haemodynamic and respiratory effects of midazolam and flunitrazepam as induction agents in cardiac surgery

30 cardiac surgical patients were investigated for comparing the respiratory and haemodynamic repercussions of induction of anaesthesia with either flunitrazepam or 8-chloro-6-(2-fluorophenyl)-1-methyl-4H-imidazo[1,5-a] [1,4]benzodiazepine (midazolam, Ro 21-3981, Dormicum). The patients were premedicated with morphine, 0.15 mg/kg i.m., and divided into two groups: one group receiving flunitrazepam 0.03 mg/kg, the other midazolam 0.15 mg/kg injected i.v. over a 15-s period. The induction time and the respiratory depression were similar in both groups. A similar decrease in systolic, diastolic and mean arterial pressures was noted, with maximum decrease of mean arterial pressure of 21% 5 min after injection of flunitrazepam, and of 19% after injection of midazolam. Midazolam produced a significant but transient pulse acceleration of 4% 1 min after the injection, while flunitrazepam produced a moderate decrease of the heart rate. These results indicate that in cardiac surgical patients midazolam produces a moderate respiratory and cardiovascular depression similar to flunitrazepam