Nitric oxide added to the sweep gas infusion reduces local clotting formation in adult blood oxygenators

Nitric oxide (NO) is an inhibitor of platelet aggregation. We analyzed the effect of direct infusion of NO into adult blood oxygenators on local clot formation. Nonheparinized calves in a control group (n = 3) and NO group (n = 4) were connected to a jugulocarotid cardiopulmonary bypass (CPB; centri fugal pump) for 6 hours. The venous line and pumphead were heparin coated, whereas the oxygenator, the heat exchanger, and the arterial line were not. A total of 80 ppm of NO was mixed with the sweep gas infusion in the NO gr oup. The pressure gradient through the oxygenator (delta > gd >P.Ox.) was m onitored, and its evolution was compared between groups. Oxygenators membra nes were analyzed and photographed, allowing for calculation of the percent age of surface area covered with clots by using a computer image analysis p rogram. The delta > gd >P.Ox. reached a plateau of 193 +/- 26% of the basal value in the NO group after 120 minutes, whereas a similar plateau of 202 +/- 22% was reached after only 20 minutes in the control group (p < 0.05). The surface area of the oxygenator covered with clots was significantly red uced in the NO group (0.54 +/- 0.41%) compared with the control group (5.78 +/- 3.80%, p < 0.05). However, general coagulation parameters were not mod ified by local NO administration. The activated coagulation time remained s table between 110 and 150 seconds in both groups (p = not significant [ns]) , and there were no differences in hematocrit, thrombin time, partial throm boplastin time, or fibrinogen between groups during the 6 hours of CPB. Thu s, the mixed infusion of a continuous low dose of NO into adult oxygenators during prolonged CPB prevented local clot formation, whereas the general c oagulation pattern remained unchanged.