Postoperative analgesic requirements following flumazenil administration

The effect of flumazenil (RO 15-1788) on postoperative analgesic requirements was evaluated in 30 postoperative patients. This prospective investigation was a double-blind, placebo-controlled trial in patients undergoing general anesthesia supplemented by midazolam and fentanyl or sufentanil. Patients received either flumazenil (n = 20) or placebo (n = 10) by random assignment. Analgesic requirements were measured in morphine equivalents (MEs) and were recorded for a three-hour period following the administration of flumazenil. All patients received the assigned treatment within five minutes of arrival to the postanesthesia room. Total ME requirements were 4.1 +/- 3.8 mg for the flumazenil group and 4.5 +/- 4.6 mg (p = 0.71) for the placebo group. Patient analgesic requirements were also assessed when patients were adequately alert. For the flumazenil group this time period was 6.2 +/- 12.7 minutes versus 52.9 +/- 28.4 minutes for placebo (p less than 0.01). MEs (flumazenil 4.1 +/- 3.8 mg vs. placebo 3.7 +/- 3.2 mg) were not significantly different (p = 0.57) when similar levels of consciousness were compared. The onset of pain was more rapid with flumazenil patients as evidenced by the first analgesic dose at 15.7 +/- 25.1 minutes for the flumazenil group versus 34.7 +/- 43.7 for the placebo group; however, these data were not statistically different (p = 0.144). These results suggest that flumazenil does not increase postoperative analgesic requirements during the immediate postanesthesia period; however, patients receiving flumazenil may experience an earlier onset of postoperative pain.