A dose response study of clonidine with local anesthetic mixture for peribulbar block: A comparison of three doses

Clonidine prolongs anesthesia and analgesia of local anesthetics in various neural blocks as well as the duration of retrobulbar block. We assessed th e dose-response relationship of clonidine added to lidocaine in peribulbar block. Sixty patients undergoing cataract surgery were given peribulbar blo ck with 7 mL of 2% lidocaine and hyaluronidase with either saline (Control) or clonidine in 0.5-mug/kg (0.5 Clon), 1.0-mug/kg (1.0 Clon), or 1.5-mug/k g (1.5 Clon) doses. The onset and duration of lid and globe akinesia, globe anesthesia and analgesia, postoperative analgesic requirement, and adverse effects (hypotension, bradycardia, hypoxia, sedation, and dizziness) were recorded. The success rate and onset of block were comparable in all groups . The duration of lid and globe akinesia, globe anesthesia and analgesia wa s significantly (P < 0.01) prolonged in patients receiving 1.0 and 1.5 mug/ kg clonidine as compared with the Control group. Perioperative pain scores and analgesic requirement were significantly less in these groups. 0.5 mug/ kg clonidine did not increase the duration of anesthesia and analgesia sign ificantly. Hypotension and dizziness were observed more in patients receivi ng 1.5 mug/kg clonidine as compared with other groups. We conclude that 1.0 mug/kg clonidine with a mixture of lidocaine (2%) significantly prolonged the duration of anesthesia and analgesia after peribulbar block with limite d side effects.