Effects of Clonidine on the Requirements of Dopamine Used as a Concomitant Drug of Amrinone in Coronary Artery Bypass Surgery (CABG)

Kim, Hong Bum; Park, Seung Young; Kim, Tae Yop

Abstract

BACKGROUND: Clonidine premedication has many beneficial effects in patients undergoing CABG surgery. Amrinone, having the ability to increase cardiac performance without increasing myocardial O2 consumption, is a valuable drug in postoperative management after cardiopulmonary bypass (CPB). The use of amrinone with a catecholamine is also important clinically because the cathecholamines support perfusion pressure and the combined use exerts synergistic or additive effects. We performed this study to examine whether clonidine premedication could change the amount of dopamine used concomitantly with amrinone for management after CPB.
METHODS
Nineteen patients for elective CABG were allocated to two groups according to their premedication; a placebo (Group 1, n = 13) or clonidine 4 microgram/kg p.o. (Group 2, n = 6). All patients arrived in the operating room with infusion of isosorbide dinitrate (ID). Anesthesia was performed with standard techniques. Before initiation of CPB, significant lowering of BP or HR was treated with phenylephrine or atropine respectively. Amrinone was given bolus (0.75 mg/kg) and infusion (10 microgram/ kg/min) was begun instead of ID at the release of aortic cross-clamp. Dopamine infusion (3 microgram/kg/min) was started at 35degree C (rectal) and its rate was adjusted for maintaining acceptable hemodynamics. We compared the amount of infused dopamine within 90 mins after CPB between the two groups. We also compared systolic BP, HR and CVP before induction, 10 mins after induction and 60 mins after CPB.
RESULTS
Systolic BP and HR before induction and HR 10 mins after induction were significantly lower in Group 2 (P < 0.05), but they were all within normal range. The proportion of patients who needed phenylephrine or atropine before CPB was not significantly different in the two groups. The amount of infused dopamine was significantly larger in Group 2 (P < 0.05). Hemodynamics were acceptable after CPB although HR 60 min after CPB was significantly lower within the normal range in Group 2 (P < 0.05). Weaning time from CPB was not significantly different in the two groups. No significant adverse effect was observed throughout this study.
CONCLUSIONS
Clonidine, used as premedication, increases the need of catecholamine which is concomitantly administered with amrinone for weaning from CPB. But this method provides clinically effective result without jeopardizing hemodynamics in CABG.