The influence of intramuscularly administered pethidine on the amnesic effects of intravenous diazepam during intravenous regional anaesthesia.

Patients undergoing surgery under regional anaesthesia often receive narcotic analgesics for premedication which may modify the sedative and amnesic effects of intravenously administered diazepam. Sixty-two patients scheduled for upper extremity surgery under intravenous regional anaesthesia received 0.15 mg/kg of diazepam intravenously to supplement the local anaesthesia. Thirty-two of the patients received 0.01 mg/kg of atropine plus 1 mg/kg of pethidine and 30 patients only atropine intramuscularly approximately 1 h before injection of diazepam. Another 30 patients received the same atropine-pethidine premedication and saline intravenously, and served as a reference group. Atropine-pethidine premedication followed by saline did not produce any amnesic effects. Sixty-nine and 38% of patients receiving atropine-pethidine premedication followed by diazepam did not remember a picture shown to them 15 min after diazepam injection or the performance of operation, respectively, the respective figures for patients given atropine premedication followed by diazepam being only 23% and 0% (P less than 0.01 - 0.001 between groups). The anti-recall of painful stimulus (exanguination) was significantly (P less than 0.01) more common when diazepam was given after pethidine premedication (31%) when compared to its injection after atropine alone (7%). The drowsiness produced by the drugs was greatest and the overall patient acceptability of the technique used most satisfactory when pethidine was used for premedication and diazepam for sedation. It is concluded that intramuscularly administered pethidine potentiates the amnesic action of intravenous diazepam for painful stimuli, prolongs the amnesic action of diazepam for visual stimuli and improves the patients' acceptability of intravenous regional anesthesia supplemented by intravenous diazepam.