Introduction. Pulmonary vascular injury induced by cardiopulmonary bypass (CPB) results in pulmonary hypertension with right ventricular dysfunction. Although inhaled nitric oxide (iNO) has been used clinically to treat lung disease, its role in the protection of lung injury has not been described. We hypothesized that starting iNO therapy before CPB would reduce post-CPB pulmonary hypertension and improve right ventricular efficiency. Methods. Twelve neonatal swine (2.1 - 2.8 kg) were randomized to CPB with (n=6) or without (n=6) iNO. In the treatment group, iNO(20ppm) was started before CPB and continued throughout data collection. Ninety minutes of low-flow CPB (35 mL/kg/min) was performed at 18°C to simulate clinical practice. Cooling and warming occurred at 100 mL/kg/min. Data were obtained before and 30, 60, and 90 minutes following CPB. Results. iNO improved pulmonary vascular resistance (PVR), pulmonary artery pressure (PAP), and right ventricular efficiency (RV eff) (see table: * p < 0.05 vs control, compared by repeated measures analysis of variance). Cardiac output (CO), A-a gradient, mean airway pressure, and oxygen delivery were not statistically different between groups. Conclusion. Initiating iNO before CPB improves pulmonary vascular mechanics and, thus, suggests a possible protective role of iNO against CPB-induced pulmonary vascular injury.

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