Oral clonidine reduces myocardial ischemia in patients with coronary artery disease undergoing noncardiac surgery.

Background: To access the clinical effect of clonidine on reduction of myocardial ischemia events in patients with history of coronary artery disease undergoing noncardiac surgeries.

Methods: Sixty ASA class III patients with coronary artery disease were allotted at random to two groups in a prospective, double-blind study to receive either clonidine (3 micrograms/kg) or placebo (control group) 90 minutes before arrival at the operating room. Continuous EKG monitoring (Holter monitor) was performed to analyze the ST segment in lead II, V2 and V5 during the preoperative (since late hours the night before operation), intraoperative and early postoperative periods (total monitoring time = 24 hours). The episode of myocardial ischemia defined as the magnitude of ST segment depression of at least 1 mm, occurring 60 ms after the J point and persisting for three minutes or more was recorded. Perioperative hemodynamic data were analyzed with two-way ANOVA with repeated measures. Student's t-test for unpaired data was used for analysis of demographics. Chi-square test was used for ST segment changes. Results are expressed as mean +/- SD and P < 0.05 was considered to be statistically significant.

Results: In the control group, 9 patients (30%) were noted to have episodes of ischemia preoperatively, 7 patients (23.3%) intraoperatively, and 12 patients (40%) postoperatively. The occurrence of myocardial ischemia peaked in the early postoperative period (P < 0.05). On the contrary, in the clonidine group, 10 patients (33.3%) saw ischemic episodes preoperatively, 3 patients (10%) intraoperatively and 5 patients (16.7%) postoperatively. The incidence of myocardial ischemia in clonidine group was significantly lower than that in placebo group in intraoperative and postoperative periods. The mean arterial pressure was significantly lower in some clonidine-treated patients during perioperative periods (P < 0.05). A number of patients in clonidine group suffered from drowsiness (66.7%) after operation (P < 0.05), but they could be easily aroused. In regard to dryness of mouth, nausea and vomiting clonidine and control groups did not differ much (P > 0.05). Demerol consumption was significantly lower in clonidine group (43.7 +/- 4.6 mg) than in control group (76.3 +/- 3.7 mg, P < 0.05).

Conclusions: We conclude that premedication with oral clonidine can significantly reduce the incidence of perioperative myocardial ischemia in patients with CAD undergoing noncardiac surgeries. The incidence of myocardial ischemia in these patients is rather high during perioperative period, which deserves our exceptional caution.