THE PERIPHERAL EFFECT OF FENTANYL ON POSTOPERATIVE PAIN

The clinical value of the analgesic effect of opioids administered per ipherally (except for intraarticular administration) has not been clea rly demonstrated. The aim of this study was to test the hypothesis tha t fentanyl, added to a local anesthetic for wound infiltration, can en hance postoperative analgesia via a peripheral mechanism. Patients wit h inguinal herniorrhaphy performed under spinal anesthesia were random ly assigned to one of two groups (n = 10 each). At the end of surgery, the wound was infiltrated with 10 mt of lidocaine 0.5% and fentanyl 0 .001% (10 mu g) in one group; in the other group, the wound was infilt rated with 10 mt of Lidocaine 0.5% alone (and fentanyl 10 mu g IM cont ralaterally). The following variables were determined in a double-blin d manner: the duration of anesthesia (response to a von Prey filament) , the duration of analgesia (time to mild postoperative pain), postope rative meperidine consumption, intensity visual analog scale of sponta neous and movement-associated pain 24 h after surgery, and wound pain threshold 24 h after surgery (pressure algometry). The addition of fen tanyl for wound infiltration enhanced the duration of anesthesia (130 +/- 37 vs 197 +/- 27 min; P < 0.001) and decreased the intensity of sp ontaneous (50 +/- 17 vs 19 +/- 18; P < 0.002) and movement-associated (56 +/- 15 vs 26 +/- 21 mm; P < 0.002) pain 24 h postoperatively. Diff erences between groups for other variables were not statistically sign ificant. Fentanyl added to a local anesthetic for wound infiltration a fter spinal anesthesia can enhance postoperative analgesia by a periph eral mechanism. Implications: Fentanyl can enhance analgesia by a peri pheral mechanism. Added to a local anesthetic for wound infiltration, it may be of benefit for the relief of postoperative pain.