Remifentanil and fentanyl during anaesthesia for major abdominal and gynaecological surgery. An open, comparative study of safety and efficacy

Background and objective This open, multicentre study compared the efficacy and safety of remifentanil with fentanyl during balanced anaesthesia with 0.8% isoflurane (end-tidal concentration) for major abdominal and gynaecolo gical surgery, and the efficacy and safety of remifentanil for pain managem ent in the immediate postoperative period. Methods Two-hundred and eighty-six patients were randomized to receive remi fentanil 1 mug kg(-1) followed by 0.2 mug kg(-1) min(-1) (n = 98), remifent anil 2 mug kg(-1) followed by 0.4 mug kg(-1) min(-1) (n = 91) or fentanyl 3 mug kg(-1) (n = 97) at induction. Thereafter, the study opioids and isoflu rane were titrated to effect during the operation. Results Compared with fentanyl, remifentanil 2 mug kg(-1) followed by 0.4 m ug kg(-1) min(-1) reduced the incidence of response to tracheal intubation (30% vs. 13%, P < 0.01), skin incision (33% vs. 4%, P < 0.001) and skin clo sure (11% vs. 3%, P < 0.05), respectively. Patients receiving remifentanil 1 <mu>g kg(-1) followed by 0.2 mug kg(-1) min(-1) had fewer responses to sk in incision than the fentanyl group (12% vs. 33%, P < 0.001), but the incid ences of response to tracheal intubation and skin closure were similar. Sig nificantly fewer patients in both remifentanil groups had ! 1 responses to surgical stress intraoperatively compared with fentanyl (68% and 48% vs. 87 %, P < 0.003). The mean isoflurane concentrations required were less in bot h remifentanil groups compared with the fentanyl group (0.1%, P = 0.05). In remifentanil-treated patients, continuation of the infusion at 0.1 mug kg( -1) min(-1) with titration increments of +/- 0.025 mug kg(-1) min(-1) was e ffective for the management of immediate postoperative pain prior to transf er to morphine analgesia. However, a high proportion of patients experience d at least moderate pain whilst the titration took place. Conclusions Anaesthesia combining isoflurane with a continuous infusion of remifentanil was significantly more effective than fentanyl at blunting res ponses to surgical stimuli. Significantly fewer patients responded to trach eal intubation with remifentanil at 0.4 mug kg(-1) min(-1), supporting the use of a higher initial infusion rate before intubation. Both remifentanil and fentanyl were well-tolerated, with reported adverse events typical of m u -opioid agonists.