• J L Pedersen, M E Crawford, J B Dahl, J Brennum, and H Kehlet.
• Department of Surgical Gastroenterology, Hvidovre Hospital, University of Copenhagen, Denmark.
• Anesthesiology. 1996 May 1;84(5):1020-6.

BackgroundPostoperative pain relief may be improved by reducing sensitization of nociceptive pathways caused by surgical trauma. Such a reduction may depend on the timing and efficacy of analgesia and the duration of the nociceptive block versus the duration of the nociceptive input. We examined whether a prolonged nerve block administered before a superficial burn injury could reduce local inflammation and late hyperalgesia after recovery from the block.MethodsThe effects of a preemptive saphenous nerve block on primary and secondary hyperalgesia, skin erythema, and blister formation, were compared to the opposite unblocked leg for 12 h after bilateral thermal injuries (15 x 25 mm, 49 degrees C for 5 min) in 20 healthy volunteers. Recovery from the block was identified by return of sensation to cold.ResultsSix subjects were excluded because of insufficient initial block (2 subjects) or because the block lasted beyond the study period (4 subjects). The remaining 14 subjects experienced significantly reduced primary (P = 0.005) and secondary hyperplasia (P = 0.01) in the blocked leg after return of cold sensation compared to the unblocked leg. Erythema intensity and blister formation were not significantly affected by the blockade (P = 0.94 and P = 0.07, respectively).ConclusionsThese data suggest that a prolonged, preemptive nerve block reduced late hyperalgesia after thermal injury, whereas the erythema and blister formation were not significantly affected.

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