Effect of Preoperative and Intraoperative Clonidine for Patients Undergoing Coronary Artery Bypass Graft Surgery

Abstract

Coronary artery bypass graft (CABG) remains the gold standard treatment today for patients with multi-vessel disease.The indications of CABG are well clear and identified and the results relatively satisfying in terms of morbidity and mortality. Anesthesia in cardiac surgery is one of the most difficult field of anesthesiology. The most difficult patients, whose adaptive reserve of cardiovascular system is very poor, are met in this field. These patients have ischemic heart disease and arterial hypertension often. All these factors increase the risk of anesthesia. So it is very important to choose medications thoroughly and save the compensatory mechanisms of cardiovascular system under conditions of surgical stress. Clonidine is the central agonist of alpha 2-adrenoreceptors. It activates alpha 2-adrenoreceptors in the brain and suppresses excretion of norepinephrine. This way the sympathetic impulse from the central nervous system to the internal organs is decreased. Clonidine is considered to be alpha 2-adrenoreceptors antihypertensive medication which suppresses sympathetic impulse from the vasomotor center in the brain. It effectively decreases mean arterial blood pressure, cardiac output, stroke volume and heart rate. Clonidine enhances sedation and analgesia. It was noticed that patients who were premedicated with clonidine, were calm and indifferent to the setting, that those premedicated with benzodiazepines. They don't react to the punction and catheterization of central vein and artery and do not need any additional sedation. The deeper sedation is achieved without the risk of hypoventilation. The purpose of this study is to assess the efficacy of clonidine in achieving preoperative and intraoperative hemodynamic stability and decrease stress response in patients undergoing coronary artery bypass grafting. Two groups, control and clonidine were made. Twenty patients, of ASAII category, were involved in each group. We gave clonidine group 5ug/kg oral premedication 60 min prior to surgery and 4ug/kg IV over 60 sec immediately just before induction of anesthesia and 1-2 ug/kg IV10 min before end of surgery, while for control group we gave them a single dose placebo. Then all patients in the 2 groups will be assessed and monitored at different times for different measurements.