Assessment of the Effect of Clonidine on Pain, Arterial and Intraocular Pressure and Arrhythmias for Cataract Surgery

After approved by the Ethical Committee and signed informed consent, 40 patients aged from 40 until 80 years undergoing cataract extraction will be randomized in two groups. Exclusion criteria will be myocardial ischemia, psychiatric disease, chronic pain, drugs dependency, chronic use of beta-blockage channel drugs. Group 2, patients will receive a single dose of 4mcg.kg-1 of clonidin2, 20 minutes before the surgical incision; group 1, patients will receive a sterile saline solution dose. Pain intensity will be assessed with the numeric rating scale. The antiarrythmic effect will be assessed with the continuous measure by Holter. The number of patients was calculated by Instat Graph® program. To detect difference in pain intensity of 3 between the groups by NRS, with 95% of power (estimated SD= 2.0), when the alpha level is set at 0.05, the sample should be of 20. Statistical analyses will be performed with parametric and nonparametric tests, considering the variety studied. The statistical program that will be utilized is Instat Graph®.