Effect on postoperative analgesia of small-dose lysine acetylsalicylate added to prilocaine during intravenous regional anesthesia

Nonsteroidal antiinflammatory drugs act largely peripherally by blocking the local synthesis of prostaglandins. The aim of this study was to evaluate whether the addition of a small dose of lysine acetylsalicylate (LA) to the prilocaine used for intravenous regional anesthesia (IVRA) would improve the quality of postoperative analgesia. Sixty patients undergoing lower extremity IVRA for foot or ankle surgery were randomly assigned to three double-blind groups: LA-IVRA where 90 mg of LA was mixed with prilocaine 0.5% for IVRA and 1 mt of 0.9% NaCl administered intravenously (IV) through the forearm catheter after tourniquet inflation; LA-TV where 1 mt of 0.9% NaCl was mixed with prilocaine and 90 mg of LA administered TV; and placebo where 1 mt of 0.9% NaCl was administered both with prilocaine for the IVRA and IV. Duration of analgesia (time elapsed between tourniquet release and first injection of morphine, expressed as mean +/- so) was significantly longer (P < 0.05) in LA-IVRA (387 +/- 216 min) when compared with LA-IV (175 +/- 264 min) and placebo (126 +/- 201 min). Analgesic requirements remained significantly lower in LA-IVRA when compared with placebo only during the first six postoperative hours, LA-IV being in an intermediate position. Pain scores were significantly lower in LA-IVRA during the first postoperative hour when compared with LA-IV and during the first 3 postoperative hours when compared with placebo. We conclude that 90 mg of LA (corresponding to 50 mg of acetylsalicylic acid) added to prilocaine 0.5% during IVRA improves the quality of postoperative analgesia in the early postoperative period.