Effect of Exogenous Nitric Oxide during Cardiopulmonary Bypass on Lung Postperfusion Histology

We tested the hypothesis that nitric oxide (NO) administered during cardiopulmonary bypass (CPB) would preserve platelets and prevent postperfusion lung changes. Ten anesthetized Yorkshire pigs were put on normothermic CPB (right atrium to aorta) with a roller pump and membrane oxygenator for 1 hour. In the study group (n = 5), NO was delivered in the oxygenator's gas inflow line with a MiniNO system at 5-10 ppm throughout CPB. In controls (n = 5), NO was not used. Crystalloid solution and norepinephrine were used to maintain blood pressure > or = 60 mm Hg. Fifteen minutes after CPB termination, all pigs were killed with intravenous potassium chloride and exsanguinated via the right atrium. Organ samples were put in formalin solution, processed in paraffin blocks, and stained with hematoxylin and eosin. We did not observe any thrombi in any perfusion system. There were no differences observed in platelet counts and aggregation ability to ADP and collagen, or in neutrophil counts between groups. Bleeding times were similar between groups before and after CPB. Also, there was no significant difference in factor XIIa and fibrinopeptide A levels between groups. Methemoglobin did not exceed normal levels. Lungs were devoid of neutrophils after perfusion in NO-treated pigs, whereas many neutrophils were present in the respiratory membrane of controls. Low-dose exogenous NO in the oxygenator's gas intake has no demonstrable effect on platelet number or function, but prevents neutrophil adhesion to lungs with a possible beneficial effect on postperfusion pulmonary morbidity.