• Jean-Pierre Estèbe, Marc E Gentili, Pascal Le Corre, Roger Le Verge, Jacques-Philippe Moulinoux, and Claude Ecoffey.
• Service d'Anesthésie Réanimation Chirurgicale 2, Laboratoire de Pharmacie Galénique et Biopharmacie, Rennes, France. jean-pierre.estebe@chu-rennes.fr
• Can J Anaesth. 2002 Aug 1;49(7):690-3.

PurposeThe aim of this study was to evaluate the effect of different durations of local anesthetic neural blockade on hyperalgesia after carrageenan infiltration in a rat model.MethodsInflammation was obtained by injection of carrageenan in the righ hind paw. Hyperalgesia was determined by measuring the threshold of response to increasing mechanical stimuli on the contralateral and on the ipsilateral paw. The development of edema was measured. After identification of the sciatic nerve by nerve stimulation, blockade was performed either one hour before or after carrageenan infiltration. Animals were randomly assigned into three groups: without sciatic nerve block (control group; n = 20), block with bupivacaine (B) and block with bupivacaine-loaded microspheres (B-Ms) injection before or after carrageenan infiltration (n = 10 for each group).ResultsCarrageenan infiltration in the control group induced a severe ipsilateral and contralateral hyperalgesia. After blockade with B (duration = 2 +/- 0.5 hr) hyperalgesia was present and delayed only by the duration of the local anesthetic effect. A longer duration of block achieved with B-Ms (duration greater than five hours), was associated with the absence of development of both ipsilateral and contralateral hyperalgesia. No preemptive effect was recorded.ConclusionB-Ms as a drug delivery system prolongs the duration of neural blockade and avoids hyperalgesia phenomena in this rat model of inflammation.

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