Clonidine as pre-anesthetic medication in cataract extraction: comparison between 100 microg and 200 microg

The objective of the present study was to evaluate the degree of sedation, intraocular pressure, and hemodynamic changes with premedication with low doses of oral clonidine, 100 microg and 200 microg, in outpatient cataract surgeries.

This is a randomized, double-blind, clinical study undertaken at the Universidade Federal de São Paulo with 60 patients of both genders, physical status ASA 1 and 2, ages 18 to 80 years. Patients were separated into three groups: placebo, clonidine 100 microg, and clonidine 200 microg. Intraocular pressure, heart rate, and blood pressure besides assessment of sedation were measured before and 90 minutes after the administration of clonidine. Sedation levels were classified according to the Ramsay sedation scale.

Patients who received placebo and 100 microg of clonidine did not show reduction in heart rate, while a reduction in heart rate was observed in patients who received 200 microg of clonidine, and this difference was statistically significant. Patients who received 200 microg of clonidine also had a reduction in systolic and diastolic blood pressure (p < 0.05). One patient who received 200 microg of clonidine developed severe hypotension, with systolic pressure < 80 mmHg. Patients treated with clonidine had a reduction in intraocular pressure (p < 0.05). Ninety minutes after the oral administration of placebo and 100 microg and 200 microg of clonidine, 25%, 60%, and 80% of the patients respectively were classified as Ramsay 3 or 4.

Clonidine 100 microg can be indicated as premedication for fasciectomies, being effective in sedation and reduction of intraocular pressure, without adverse effects on blood pressure and heart rate.