Fentanyl Patches to Supplement Ultrasound-Guided Nerve Blocks for Improving Pain Control After Foot and Ankle Surgery: A Prospective Study.

The analgesic effects of preoperative ultrasound-guided nerve blocks wear off after about 12 hours, leaving some patients in substantial pain. Transdermal fentanyl concentrations peak at 12 to 24 hours after application and maintain this concentration for approximately 72 hours. We sought to determine whether combining the use of a transdermal fentanyl patch with either a sciatic or femoral-sciatic nerve block would improve pain control in patients undergoing foot and/or ankle surgery. Consecutive patients in the no-patch control group (n = 104) were enrolled from July 2011 to October 2011, and those in the treatment group (n = 232) were enrolled from November 2011 to May 2012 and received a transdermal patch (4.125 mg/7.5 cm(2) releasing 25 μg of fentanyl per hour) applied to their chest postoperatively. Pain was assessed using a visual analog scale at 6, 12, 24, and 48 hours after surgery. The primary outcome measure was the number of requests for additional postoperative pain medication. Additional postoperative analgesia was requested by 49 of the 104 control patients (47.1%) and 63 of the 232 treated patients (27.1%; p = .002). The mean pain scores were also lower in the treatment group, with a statistically significant difference (p < .05) at 12, 24, and 48 hours. Thus, patients receiving a fentanyl patch combined with an ultrasound-guided nerve block required less supplemental analgesia to maintain adequate pain control than did those receiving a nerve block alone. In conclusion, a fentanyl patch is a useful adjunct to an ultrasound-guided nerve block in foot and ankle surgery.