Axillary brachial plexus block with clonidine or verapamil

ABSTRACT

The ability of a[2]-agonists to enhance central and peripheral neural blockade. when added to local anesthetic, has been demonstrated for more than a decade. Calciumions also have an important role in the analgesia mediated by local anesthetics, and clinical investigation have shown that verapamil can potentiate the analgesic effect of local anesthetics. Seventy five unpremedicated patients ASA physical status I or II undergoing upper extremity surgery received axaillary brachial plexus block with 40 ml lidocaine 1.5% solution. Patients were randomized to 3 groups. Group I [control group] received only 40 ml of 1.5% lidocaine solution. Group 2 [clonidine group] received 40 ml 1.5% lidocaine solution to which 150 ug clonidine was added. Group 3 [verapamil group] received 40 ml 1.5% lidocaine solution to which 2.5 mg verapamil was added. Onset of sensory block, duration of anesthesia and analgesia were recorded. Postoperatively patients rated their pain on integer verbal pain score [0-10] at 1, 3, 6, 12 and 24 hour. Postoperatively patients were instructed to take paracetamole [500 mg increments every 6 h up to 4 gm / day] when pain score exceeded 3. The onset of sensory block was similar among the three groups. Duration of sensory anesthesia was significantly increased P<0.01 in group [3] compared to group [1]. The duration of analgesia significantly increased in group [2] P<0.01 compared to group 1 and 3. We conclude that addition of clonidine to lidocaine during axillary brachial plexus block prolong the duration of analgesia. While addition of verapamil to lidocaine during axillary brachial plexus block significantly increase the duration of anesthesia