EFFECTS OF ORGANIC NITRATE VASODILATORS ON PLATELET-FUNCTION BEFORE AND AFTER CARDIOPULMONARY BYPASS

Various in vitro, ex vivo and in vivo tests have shown that organic ni trates attenuate platelet function. Because organic nitrates are commo nly administered to patients undergoing cardiac surgery, the postopera tive bleeding tendency observed in these patients might be strengthene d by nitrates. Therefore, we compared the acute effects of nitroglycer in (0.5 mu g kg(-1) min(-1)) and isosorbide dinitrate (0.5 or 2.5 mu g kg(-1) min(-1)) with those of placebo on platelet function both befor e and after cardiopulmonary bypass in 40 patients undergoing coronary artery bypass grafting (CABG). Bleeding time, platelet retention on gl ass beads, i.e, platelet adhesiveness, and thromboelastograph tracings were used as indicators of platelet function. Although nitroglycerin and isosorbide dinitrate induced significant haemodynamic changes, e.g . decreases in arterial and pulmonary arterial pressure, they had no s ignificant effects on the indices of platelet function. We conclude th at, when given in haemodynamically effective doses, neither nitroglyce rin nor isosorbide dinitrate have any measurable acute effect on plate let function as evaluated with on-site tests in patients undergoing CA BG surgery.