Exhaled nitric oxide level decreases after cardiopulmonary bypass in adult patients

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Abstract
To measure exhaled nitric oxide (NO) and compare it with lung function after cardiopulmonary bypass (CPB) in adult patients. Pulmonary dysfunction is sometimes observed after CPB. Impaired production of NO may account for this dysfunction. Prospective, single-center, observational study. University hospital operating room, intensive care unit. Sixteen adult patients undergoing cardiac surgery with CPB. None except cardiac surgery with CPB. Exhaled NO was measured continuously by the chemiluminescence method and was expressed as the peak and mean NO concentrations, and the NO output (VNO). These parameters were calculated by averaging four sequential tidal NO values. The data were obtained serially from before CPB to 16 hrs after CPB. Lung function was evaluated by monitoring lung compliance, pulmonary artery pressure, and alveolar–arterial oxygen difference (P(a-a)o2). The cardiac index did not change except for a significant increase at 16 hrs compared with 6 hrs after CPB. Peak NO, mean NO, and VNO decreased from 15.4 ± 2.0 ppb (before CPB) to 8.2 ± 0.8 ppb (6 hrs after CPB), from 5.7 ± 0.7 ppb to 2.8 ± 0.6 ppb, and from 29.2 ± 3.1 nL/min to 15.7 ± 2.2 nL/min, respectively. These changes were associated with the increases in pulmonary artery pressure and alveolar–arterial oxygen difference, and the decrease in lung compliance. VNO recovered to the level measured before CPB 16 hrs after CPB, which was consistent with the physiologic recovery in pulmonary hypertension, lung compliance, and gas exchange. Measurement of exhaled NO as VNO, which was associated with lung dysfunction, may be an indicator of lung injury in adult patients after cardiopulmonary bypass.