Adding clonidine to mepivacaine prolongs the duration of anesthesia and analgesia after axillary brachial plexus block.

BACKGROUND AND OBJECTIVES: This study evaluates the effects of clonidine added to mepivacaine on the duration of anesthesia and analgesia after axillary brachial plexus block.

METHODS: Thirty patients scheduled for elective hand surgery were divided into three equal groups in a randomized, double-blinded fashion. An axillary perivascular brachial plexus block was performed with 40 ml 1% mepivacaine plus 1:200,000 epinephrine in the three groups. Group B also received 150 micrograms clonidine subcutaneously and Group C had the same dose of clonidine mixed with the local anesthetic and injected into the plexus sheath. The following variables were recorded: onset time, duration of anesthesia, duration of analgesia, postoperative pain score, intake of analgesics, and adverse effects.

RESULTS: The three groups were comparable in terms of age, sex, weight, height, onset time of anesthesia, postoperative pain score, and analgesic requirement. The duration of anesthesia and analgesia was comparable in Groups A and B, but both variables were significantly increased in Group C: the duration of anesthesia and analgesia were prolonged, respectively, by 37 +/- 6% and 103 +/- 16% when compared to Group A and by 32 +/- 7% and 89 +/- 15% when compared to Group B. No side effects were reported.

CONCLUSIONS: One hundred fifty micrograms clonidine added to mepivacaine for brachial plexus block prolongs the duration of anesthesia and analgesia. Our results suggest that this effect of clonidine is local rather than systemic.