The Peripheral Effect of Fentanyl on Postoperative Pain

MD, PhDs *Department of Anesthesia, Rebecca Sieff Government Hospital, Safed; Departments of tAnesthesia and SSurgery, Poria Government Hospital, Poria, Israel; and aDepartment of Anesthesia, Harvard Medical School, Brigham and Women’s Hospital, Boston, Massachusetts The clinical value of the analgesic effect of opioids ad- ministered peripherally (except for intraarticular ad- ministration) has not been clearly demonstrated. The aim of this study was to test the hypothesis that fenta- nyl, added to a local anesthetic for wound infiltration, can enhance postoperative analgesia via a peripheral mechanism. Patients with inguinal herniorrhaphy per- formed under spinal anesthesia were randomly as- signed to one of two groups (n = 10 each). At the end of surgery, the wound was infiltrated with 10 mL of lido- Caine 0.5% and fentanyl 0.001% (10 pg) in one group; in the other group, the wound was infiltrated with 10 mL of lidocaine 0.5% alone (and fentanyl 10 Fg IM con- tralaterally). The following variables were determined in a double-blind manner: the duration of anesthesia (response to a von Frey filament), the duration of anal- gesia (time to mild postoperative pain), postoperative meperidine consumption, intensity visual analog scale of spontaneous and movement-associated pain 24 h af- ter surgery, and wound pain threshold 24 h after sur- gery (pressure algometry). The addition of fentanyl for wound infiltration enhanced the duration of anesthesia (130 2 37 vs 197 2 27 min; P < 0.001) and decreased the intensity of spontaneous (50 i 17 vs 19 t 18 mm; P < 0.002) and movement-associated (56 5 15 vs 26 2 21 mm; P < 0.002) pain 24 h postoperatively. Differ- ences between groups for other variables were not sta- tistically significant. Fentanyl added to a local anes- thetic for wound infiltration after spinal anesthesia can enhance postoperative analgesia by a peripheral mech- anism. Implications: Fentanyl can enhance analgesia by a peripheral mechanism. Added to local anesthetic for wound infiltration, it may be of benefit for the relief of postoperative pain. (Anesth Analg 1998;87:11214)