The effect of nitric oxide on platelets when delivered to the cardiopulmonary bypass circuit

Nitric oxide (NO) decreases platelet adhesion to foreign surfaces in the in vitro models of cardiopulmonary bypass (CPB). We hypothesized that NO, del ivered into the membrane oxygenator (MO), would exert a platelet-sparing ef fect after CPB. Forty-seven patients scheduled for coronary artery surgery were randomized to either a NO group, in which NO (100 ppm) was delivered i nto the MO, or a control group, in which CPB was conducted without NO. Plat elet numbers, platelet aggregation response to 2.5-20 mu M adenosine diphos phate, and beta-thromboglobulin levels were measured after induction of ane sthesia, after 1 h on CPB and 2 h after the end of CPB. Met-hemoglobin leve ls were measured during CPB. The amount of blood products administered and chest tube drainage were measured in the first postoperative 18 h. NO deliv ered into the MO for up to 180 min did not increase met-hemoglobin levels a bove 4%. NO inhibited the platelet aggregation response to 2.5 mu M ADP dur ing CPB, otherwise NO had no other detectable effect on the aggregation res ponses or the levels of beta-thromboglobulin. Platelet numbers were not sig nificantly altered by NO. NO did not alter the use of blood products or che st tube drainage. in conclusion, this study suggests that NO delivered into the MO of the CPB circuit does not significantly alter platelet aggregatio n and numbers, and does not affect bleeding. Implications: Nitric oxide aff ects platelet function. We demonstrated that nitric oxide delivered into th e gas inflow of the cardiopulmonary bypass circuit membrane oxygenator does not significantly alter platelet numbers or function.