REMIFENTANIL IN COMBINATION WITH PROPOFOL FOR SPONTANEOUS VENTILATIONANESTHESIA

We have investigated the effect of four doses of remifentanil on the i ncidence of respiratory depression and somatic response at incision. R emifentanil was administered as a loading dose of 0.125, 0.25, 0.375 o r 0.5 mu g kg(-1) and at a maintenance infusion rate of 0.025, 0.05, 0 .075 or 0.1 mu g kg(-1) min(-1), respectively, with an infusion of pro pofol 6 mg kg(-1) h(-1). Responses occurred in 88% of patients with re mifentanil 0.025 mu g kg(-1) min(-1) compared with 30-40% in the other groups. Respiratory depression after incision increased from 6% with remifentanil 0.025 mu g kg(-1) min(-1) to 73% with 0.1 mu g kg(-1) min (-1). Increases in propofol infusion rate to 7.2-8.4 mg kg(-1) h(-1) p roduced adequate maintenance of anaesthesia. Reductions in remifentani l doses to 0.025-0.05 mu g kg(-1) min(-1) resulted in adequate respira tion at the end of surgery in 88% of patients. Maintenance infusions o f the two drugs for spontaneous ventilation are likely to be in these ranges. However, the ideal loading doses and infusion rates for induct ion remain to be established.