dose response study of three different concentrations of clonidine with local anesthetic mixture for peribulbar block

Clonidine, the alpha[2] agonist prolong anesthesia and analgesia when added to local anesthetics, in epidural anesthesia, subarachnoid anesthesia, plexus anesthesia and retrobulbar block. We evaluate the dose-response relationship of different concentrations of clonidine added to lidocaine in peribulbar block. Sixty patients undergoing cataract surgery were given peribulbar block with 7-10 ml of 2% lidocaine and hyaluronidase with either saline [control] or clonidine 0.5 ug/kg [0.5 clon] 1.0 ug/ kg [1.0 clon] or 1.5 ug/kg [1.5 clon] doses. The onset of globe anesthesia, akinesia and analgesia, the duration of anesthesia and analgesia, the postoperative analgesia requirement and the adverse effects [Hypotension, bradycardia, hypoxia, sedation and dizziness] were recorded. The onset of block was comparable in all groups. The duration of globe anesthesia, analgesia and akinesia was significantly [p<0.01] prolonged in patients receiving 1.0 and 1.5 ug/kg clonidine as compared with the control group. Perioperative pain scores and analgesic requirements were significantly less in these groups. 0.5 ug/kg clonidine did not significantly increase the duration of anesthesia and analgesia. The side effects were observed more with 1.5 ug/kg clonidine as compared with other groups. We conclude that 1.0 ug/kg clonidine significantly prolong the anesthesia and analgesia when mixed with local anesthetic with minimal side effects

Axillary brachial plexus block with clonidine or verapamil

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