Small-Dose Hypobaric Lidocaine-Fentanyl Spinal Anesthesia for Short Duration Outpatient Laparoscopy. II. Optimal Fentanyl Dose

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Abstract
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 micrograms fentanyl added to 20 mg lidocaine and sterile water (total 3 mL). Administration was with 27-gauge Whitacre needles and patients sat upright until the block was > T-8. One patient in the 0-microgram fentanyl group required general anesthesia 40 min after the start of surgery, leaving 21 patients per group. Three patients in each of the 0-microgram and 10-microgram 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-microgram than 0-microgram fentanyl group, 28% vs 67% (P < 0.0166). Intraoperative supplementation with alfentanil (+/- propofol) was needed less often in the 25-microgram than 0-microgram fentanyl group, 43% vs 76% (P = 0.028). Recovery of sensation took longer in the 25-microgram than in the 0-microgram and 10-microgram 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-microgram than in the 25-microgram 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-microgram and 25-microgram groups than in the 0-microgram 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 micrograms 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.