No enhancement of sensory and motor blockade by neostigmine added to mepivacaine axillary plexus block

Background: Intrathecal neostigmine induces analgesia but also several side effects. Recently, 500 mu g neostigmine administered intraarticularly was shown to produce postoperative analgesia without side effects. The authors' goal was to determine whether 500 mu g neostigmine added to mepivacaine in axillary plexus block prolongs postoperative analgesia. In addition, they wanted to determine the incidence of side effects in patients undergoing hand surgery. Methods: Sixty-nine outpatients scheduled for car-pal tunnel syndrome repair with axillary plexus block were randomly assigned to one of three groups that received saline solution in the axillary plexus and subcutaneously (group 1), 500 mu g neostigmine in the axillary plexus and saline solution subcutaneously (group 2), or saline solution in the axillary plexus and 500 mu g neostigmine subcutaneously (group 3). Sensory and motor block in the four hand nerve distributions were assessed every 5 min for 30 min. The duration of the sensory and motor blocks were assessed after operation. Side effects were also recorded Results: Neostigmine had no effect on sensory and motor block in any of the four nerve distributions, nor did it increase the median duration of sensory block (215 min; range, 120-330 min) compared with group 1 (247 min; range, 190-287 min) or group 3 (236 min; range, 160-280 min). Motor block was slightly shorter (P = 0.045) in group 3 (190 min; range, 135-285 min) compared with group 1 (218 min; range, 145-257 min) and group 2 (215 min; range, 105-343 min). Gastrointestinal side effects occurred in 30% of patients in both neostigmine groups but not in group 1 (P < 0.05). Conclusions: This study suggests that 500 mu g neostigmine added to mepivacaine in axillary plexus block does not prolong postoperative sensory block, but it does cause a relatively high incidence of side effects. These two findings raise doubts about the use of neostigmine associated with local anesthetics for plexus neural block.