EFFECT OF NITRIC-OXIDE GAS ON PLATELETS DURING OPEN-HEART OPERATIONS

Background. The increased bleeding tendency observed after cardiopulmo nary bypass is caused in part by thrombocytopenia and impaired platele t function induced by the procedure. Previous in vitro studies have sh own that nitric oxide (NO) added to the oxygenator sweep gas reduces p latelet activation during experimental perfusion. We evaluated the eff ect of 40 ppm of NO, added to the oxygenator sweep gas, on platelet co nsumption and activation in patients undergoing cardiopulmonary bypass . Methods. Twenty patients scheduled to undergo cardiopulmonary bypass were randomized to either the control or the NO arm of the study. The ir platelet count, plasma beta-thromboglobulin level, platelet membran e glycoprotein Ib and IIb/IIIa levels, adenosine diphosphate-induced p latelet aggregation, plasma nitrate level, and plasma hemoglobin were assayed before, during, and after cardiopulmonary bypass. Results. Aft er operation, slightly higher platelet counts were observed in the NO- treated patients than in the control patients, which might indicate a lower degree of platelet adhesion to the artificial surfaces of the ex tracorporeal circuit. However, this difference did not reach statistic al significance. In addition, a difference in platelet membrane expres sion of glycoprotein Ib was seen between the NO and control groups aft er operation; the platelets of the control patients had significantly higher glycoprotein Ib expression than those of the NO-treated patient s. The results of platelet aggregometry indicated preserved platelet f unction in both the NO-treated and control patients, The blood methemo globin levels also were low in both groups. Conclusions. Nitric oxide might reduce the platelet consumption encountered during cardiopulmona ry bypass without having any adverse effect on platelet function, as r eflected by the preserved aggregation response seen in our patients. H owever, the best route of NO administration and the optimum dose remai n to be established. (C) 1998 by The Society of Thoracic Surgeons.