Time Course of Endothelin-1 and Nitrate Anion Levels After Cardiopulmonary Bypass in Congenital Heart Defects

Background. The endothelium-derived vasoconstrictor endothelin-1 (ET-1) may be involved in pulmonary hypertension (PH), but production of the endothelium-derived vasodilator nitric oxide (NO) after cardiopulmonary bypass (CPB) in congenital heart disease is unclear. Methods. Twenty patients (age, 4 months to 12 years) were divided into three groups: severe PH (mean pulmonary-to-systemic arterial pressure ratio >0.5) and high pulmonary flow (n = 8), mild PH (mean pulmonary-to-systemic arterial pressure ratio <0.35) and high pulmonary flow (n = 6), and no PH and low pulmonary flow (n = 6). The mean pulmonary-to-systemic arterial pressure ratio was calculated and blood samples were taken, and NO3−, an NO metabolite, was measured. Results. Levels of ET-1 in the group with severe PH and high pulmonary flow were higher than in the other groups until 6 hours after CPB, and NO3− was not changed significantly in the group with severe PH and high pulmonary flow and or the group with mild PH and high pulmonary flow during CPB. Endothelin-1 in the group with no PH and low pulmonary flow was higher than in the group with mild PH and high pulmonary flow after CPB, and NO3− in the group with no PH and low pulmonary flow significantly decreased after CPB. A positive correlation was obtained between mean pulmonary-to-systemic arterial pressure ratio and ET-1 (r = 0.742 before CPB; r = 0.689 after CPB). Conclusions. Imbalance between increased ET-1 and constant NO after CPB in the group with severe PH and high pulmonary flow could contribute to dominant effects of ET-1, which may injure the lung. The increased ET-1 and the decreased NO after CPB in the group with no PH and low pulmonary flow may induce a mechanism of protective vasoconstriction against an acute increase in pulmonary flow.