BACKGROUND: We hypothesized that the decreased nitric oxide after cardiopulmonary bypass and reperfusion would play an important role in temporary pulmonary hypertension.

METHODS: We used the pulmonary arteries of three pigs weighing 40-50 kg after cardiopulmonary bypass and reperfusion in experimental group. We also used the pulmonary arteries of five pigs before cardiopulmonary bypass under sham operation in control group. All cumulative concentration-effect curves were performed on vessel rings beginning at their optimum resting zone. EC₅₀ and maximal response (E_max) were calculated by using nonlineal logistic regression analysis with the software PRISM (Graphpad, Mountain View, CA).

RESULTS: CPB inhibited endothelium-dependent relaxation to acetylcholine in pulmonary arterial rings, but did not affect SNP induced relaxation in ones.

CONCLUSIONS: The Ability of pulmonary arterial relaxation after CPB and reperfusion in pigs was decreased without attenuated pulmonary arterial sensitivity to NO.