[Respiratory and sleep-inducing effects of i.m. midazolam as premedication for regional anesthesia. Comparison with diazepam, promethazine/pethidine and placebo].

The effects of respiratory depression and sleep induction produced by 0.1 mg/kg and 0.15 mg/kg of midazolam i.m. were examined in patients in whom urological interventions had to be performed under spinal anesthesia. The same parameters were evaluated for 0.2 mg/kg of diazepam i.m. as well as 50 mg/50 mg of pethidine/promethazine i.m. and placebo i.m. The major difference between 0.1 mg and 0.15 mg/kg body weight of midazolam was a more pronounced PCO2-increase in the group with the higher dosage. Both dosages led to anterograde amnesia in 8 or 9 of 10 patients respectively. No amnesia developed in the control groups. Respiratory depression and sleep induction occurred later with promethazine/pethidine (at 60 min) or diazepam (at 120 min) than with midazolam. Noteworthy in the Diazepam and placebo group was a hyperventilation lasting 60 and 120 min respectively. The arterial PO2 decreased in all groups during the intervention. Under midazolam, the decrease was significantly higher statistically than in the control groups during the first 60 min at both dosages. Premedication with 0.1 mg/kg i.m. of midazolam proved to be sufficient in all patients. The rapid onset of action, the sleep during the intervention and the amnesia associated with it suggest that this form of premedication is more favorable than the other procedures examined. The dosage of 0.15 mg/kg of midazolam proved to be too high: in addition to producing a stronger respiratory depression, it had the effect of rendering cooperation with some patients more difficult.