Background. No data are available on blood levels of local anesthetics after ankle block.
Methods. Eighteen patients received 13 ml 2% lidocaine and ten received 30 ml 0.75% bupivacaine for unilateral or bilateral midtarsal ankle blocks, respectively. Blood levels were drawn at 15, 30, 45, 60, 90, 120, and 180 minutes after injections. All patients had forefoot surgery with elastic bandages (Esmarch) applied as a tourniquet immediately above the ankle intraoperatively.
Results. The mean peak level of lidocaine was 1.1 μg/ml, and of bupivacaine, 0.5 μg/ml. The mean duration of analgesia was 17 hours with 0.75% bupivacaine. Duration could not be assessed in the lidocaine group because these were ambulatory patients.
Conclusion. The low peak level of local anesthesia and the prolonged analgesia confirmed the safety and efficacy of midtarsal ankle block for forefoot surgery and suggest that bupivacaine may be the local anesthetic agent of choice.
- regional anesthesia.
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The authors thank Richard Arthur, Ph.D., of the Department of Anesthesia, Brigham and Women's Hospital, Boston, for the gas chromatographic determinations and his comments regarding the data.