Fentanyl-prilocaine mixture for intravenous regional anaesthesia in patients undergoing surgery

The effect of the addition of 0.1 mg or 0.2 mg fentanyl to 40 ml 0.5% prilocaine in intravenous regional anaesthesia of the arm was investigated in 37 patients in a randomised, double-blind study. The characteristics of the sensory and motor block were studied. There was no difference in the speed of onset of analgesia in the groups (mean latency approximately 4 min in each group). However, significantly more patients in the fentanyl 0.2 mg group (7/12) had complete anaesthesia at 15 min than in the fentanyl 0.1 mg group (1/13) and the control group (2/12) (p less than 0.05). There were no differences in the incidence of tourniquet pain immediately before cuff deflation (tourniquet time 45-87 min). After cuff deflation, in those patients who complained of wound pain within 30 min, on average the pain appeared later in the fentanyl 0.2 mg group (six patients, mean 14.3 min) than in the control group (eight patients, mean 9.4 min) (ns). In the fentanyl groups, the incidence of central nervous system side effects was greater than in the control group (fentanyl 0.1 mg 7/13 patients, fentanyl 0.2 mg 6/12 patients, control 1/12 patients) (p less than 0.05). The plasma concentrations of prilocaine after cuff deflation were higher, in a dose-dependent fashion, in the fentanyl groups than in the control group, but the concentrations of prilocaine and fentanyl did not correlate with the symptoms. Postoperative nausea occurred only in the patients who had received fentanyl.