Effect of addition of clonidine to local anaesthetic mixture for peribulbar block

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 I ml normal saline, while group B (clonidine group) patients had clonidine I mug/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+/-17.5 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 I mug/kg to local anaesthetic mixture significantly increases the duration of anaesthesia and analgesia after peribulbar block.