A MINIMUM DOSE OF CLONIDINE ADDED TO MEPIVACAINE PROLONGS THE DURATION OF ANESTHESIA AND ANALGESIA AFTER AXILLARY BRACHIAL-PLEXUS BLOCK

This study assessed the minimum dose of clonidine required to prolong the duration of both anesthesia and analgesia after axillary brachial plexus blockade. Eighty patients scheduled for elective hand surgery w ere divided into eight groups in a randomized, double-blind fashion. A n axillary brachial plexus block was performed with 40 mt 1% mepivacai ne plus 1:200,000 epinephrine. The control group received no clonidine . In the other groups, increasing doses of clonidine (0.1, 0.2, 0.3, 0 .4, 0.5, 1, and 1.5 mu g/kg) were added to the local anesthetic soluti on. Onset time, duration of anesthesia and analgesia, postoperative pa in score, intake of analgesics, and adverse effects were recorded. The eight groups were comparable in terms of onset time, postoperative pa in score, and analgesic requirement. The minimum dose of clonidine req uired to significantly prolong the duration of analgesia and anesthesi a was, respectively, 0.1 and 0.5 mu g/kg. No side effects (sedation, d rowsiness, bradycardia, arterial hypotension) were reported. We conclu de that the dose of clonidine required to prolong significantly the du ration of both anesthesia and analgesia after axillary brachial plexus blockade is 0.5 mu g/kg and that, at this dose, clonidine may be used without important reported side effects even in outpatients.