Effect of prophylactic continuous infusion of isosorbide dinitrate on myocardial protection and hemodynamics in patients undergoing off-pump coronary bypass surgery

ABSTRACT

BACKGROUND: Multi-vessel off-pump coronary bypass surgery (OPCAB) imposes cumulative myocardial ischemia/reperfusion injury, which may be attenuated by continuous infusion of nitrate. However, nitrate infusion and consequent decrease in preload may be hazardous during heart displacement which causes restrictive filling of the ventricles. Therefore, we evaluated the effect of nitrate infusion on myocardial protection and hemodynamics in patients undergoing OPCAB, in a prospective, randomized and controlled trial. METHODS: Fifty patients with stable angina and left ventricular ejection fraction >40% undergoing elective, isolated, multivessel OPCAB were enrolled. Patients were randomized equally to either continuous infusion of isosorbide dinitrate 0.5microg/kg/min or same amount of normal saline during the surgery. Operative data including hemodynamic variables, intraoperative ST segment changes and postoperative cardiac enzyme release (creatine kinase-MB, troponin T) were compared. RESULTS: Patients characteristic and operative data including ST segment changes and use of vasopressors were similar between the groups except the total amount of infused crystalloid during the surgery which was significantly higher in the nitrate group. Postoperative variables including cardiac enzyme release were also similar between the groups. CONCLUSIONS: Prophylactic continuous infusion of nitrate during OPCAB exerted no additional benefit in terms of myocardial protection. It also, was not associated with accentuated decrease in cardiac output during heart displacement, and the decrease in preload seems to have been nullified by modest increase in fluid therapy.