Serum levels of mepivacaine-HCl during continuous axillary brachial plexus block

In order to find out whether repeated doses of plain mepivacaine are appropriate for long-lasting microvascular surgery, a catheter-induced axillary plexus block was performed in 17 patients by using 400 mg of mepivacaine-HC1 every two hours. All patients underwent replantation surgery of one or more amputated fingers. Duration of operation varied from 8 to 24 hours. In all cases, there was adequate analgesia and muscle relaxation for the surgical procedure. Serum levels of mepivacaine were determined before, and 15 and 60 minute after the initial injection. With each following injection of mepivacaine, blood samples were taken at the same time schedule. Within the first eight hours, after four 400 mg doses of mepivacaine were given, all serum levels remained below the level of 5 to 6 micrograms/ml, which is said to be the lower level for mild cerebral toxic reactions in venous blood (blood/plasma distribution 0.92 +/- 0.04). After this time, when more than 1600 mg of mepivacaine had been administered, two patients exceeded the level of 6 micrograms/ml. The highest serum concentration observed in any of the patients was 7.0 micrograms/ml. This was 15 minutes after the 12th injection of 400 mg of mepivacaine and an overall dosage of 4800 mg. None of the patients showed evident signs of central nervous system or cardiovascular toxicity.