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SUMMARY
Clonidine added to local anaesthetics prolongs the duration of anaesthesia and analgesia of peripheral, neuraxial and retrobulbar blocks. The present randomized blinded controlled study was conducted to evaluate the effect of the addition of clonidine to local anaesthetic mixture on the quality, onset time, duration of peribulbar block, perioperative analgesia and patients' comfort.
The study comprised two groups of 12 patients each. Group A (control) patients received 7 ml of a mixture of 2% lignocaine and hyaluronidase with 1 ml normal saline, while group B (clonidine group) patients had clonidine 1 (mu)g/kg added to the above mixture. Onset and duration of lid akinesia, globe anaesthesia and akinesia, time to first analgesic medication and total analgesic requirement were assessed. Patients were monitored for heart rate, blood pressure, sedation and respiratory depression.
Addition of clonidine to local anaesthetic mixture resulted in a significant increase in duration of lid akinesia (85.4 +/- 25.6 vs 173.3 +/- 35.3 min, P<0.001), globe anaesthesia (63.2 +/- 6.9 vs 78.8 +/- 175 min, P=0.012) and globe akinesia (161.3 +/- 24.3 vs 201.2 +/- 45.7 min, P=0.016). The onset time and quality of block were similar in both the groups. No significant haemodynamic, respiratory or sedative effects were recorded. The perioperative pain scores and the analgesic requirements were significantly (P<0.01) lower in group B patients. We found that addition of clonidine 1 (mu)g/kg to local anaesthetic mixture significantly increases the duration of anaesthesia and analgesia after peribulbar block.
Key Words: ANAESTHESIA, REGIONAL: peribulbar block, pharmacology, lidocaine, clonidine. SURGERY: cataract
Clonidine, a centrally active a2-agonist, was introduced as an antihypertensive agent. Recently, it has been extensively studied as an adjunct to general and regional anaesthesia because of its analgesic, anxiolytic and sedative properties1. Admixture of clonidine to local anaesthetics prolongs the duration of both anaesthesia and analgesia after various neuraxial and peripheral nerve blocks, including spinal2, epidural3, axillary plexus4, cervical plexus5 and femoral nerve block6. In ophthalmic surgery, it has been shown to decrease intraocular pressure and increase the duration of retrobulbar block when used with local anaesthetics7. However, in a study on peribulbar block, Connelly and colleagues did not find any effect of clonidine on intraocular pressure, onset time and postoperative analgesic requirement8. They did not comment on...