Dexmedetomidine as intramuscular premedication in outpatient cataract surgery. A placebo-controlled dose-ranging study.

Alpha 2 agonists have been shown to decrease intra-ocular pressure in ophthalmic surgery. We studied the effects of dexmedetomidine, a new alpha 2 agonist, on intra-ocular pressure, haemodynamic parameters, sedation, anxiolysis and dryness of mouth in 35 (ASA physical status 1-3) patients undergoing day-case cataract surgery under peri-ocular anaesthesia. Five different doses of dexmedetomidine (0.25, 0.5, 0.75, 1.0 and 1.5 micrograms.kg-1) were used in this double-blind, randomised and placebo-controlled study. The trial drug was administered into the deltoid muscle 60 min before surgery. The 1.0 micrograms.kg-1 dose of dexmedetomidine produced a 32% reduction of intra-ocular pressure (p = 0.002). This dose induced moderate sedation, but was not associated with significant haemodynamic changes. A significant decrease in heart rate and systolic blood pressure was seen only with the highest dose of dexmedetomidine. Our results suggest that dexmedetomidine 1.0 micrograms.kg-1 produces sedation and a reduction of intra-ocular pressure with minimal haemodynamic side effects when given intramuscularly as premedication before cataract surgery under regional anaesthesia.