Small-dose hypobaric lidocaine-fentanyl spinal anesthesia for short duration outpatient laparoscopy .2. Optimal fentanyl dose

We performed a double-blind, controlled trial to determine the optimal dose of intrathecal fentanyl in small-dose hypobaric lidocaine spinal anesthesia for outpatient laparoscopy. Sixty-four gynecological patients were randomized into three groups, receiving 0, 10, or 25 mu g fentanyl added to 20 mg lidocaine and sterile water (total 3 mt). Administration was with 27-gauge Whitacre needles and patients sat upright until the block was >T-8. One patient in the 0-mu g fentanyl group required general anesthesia 40 min after the start of surgery, leaving 21 patients per group. Three patients in each of the 0-mu g and 10-mu g fentanyl groups had mild discomfort with trocar insertion, or return of some sensation and felt discomfort or sutures toward the end of surgery. Shoulder-tip pain was less frequent in the 25-mu g than 0-mu g fentanyl group, 28% vs 67% (P < 0.0166). Intraoperative supplementation with alfentanil (+/- propofol) was needed less often in the 25-mu g than 0-mu g fentanyl group, 43% vs 76% (P = 0.028). Recovery of sensation took longer in the 25-mu g than in the 0-mu g and 10-mu g fentanyl groups, 101 +/- 21 vs 84 +/- 20 and 87 +/- 18 min(P < 0.05), although motor recovery and discharge times were the same. Postoperative analgesia was needed earlier in the 0-mu g than in the 25-mu g fentanyl group, median 54 (13-120) vs 87 (65-132) min (P < 0.05). Pruritus was the only side effect that occurred more often in the 10-mu g and 25-mu g groups than in the 0-mu g fentanyl group, 62% and 67% vs 14% (P < 0.0166). One patient required an epidural blood patch for postdural puncture headache. Based on these results, we concluded that 25 mu g intrathecal fentanyl is required when 20 mg lidocaine is used for hypobaric spinal anesthesia (SA) to ensure reliable, durable anesthesia, reduce shoulder-tip pain, and minimize the need for intraoperative supplementation. This dose provides longer postoperative analgesia and does not increase side effects apart from pruritus. SA with small-dose hypobaric lidocaine-fentanyl was found to be a satisfactory technique for outpatient laparoscopy, although postdural puncture headache can occur in some patients.