Pulmonary vasoreactivity and vasoactive mediators in children with pulmonary hypertension.

Abstract

We assessed the effect of oxygen, nitric oxide (NO) and prostanoids (prostacyclin and iloprost) on pulmonary hemodynamics and plasma levels of vasoactive mediators in children with pulmonary hypertension (PH). It is not known whether the hemodynamic response during acute vasodilator testing correlates with changes in plasma levels of endothelin-1 (ET-1), cyclic guanosine monophosphate (cGMP) and cyclic adenosine monophosphate (cAMP). In this retrospective analysis 14 children at a median age of 4 years and 3 months [1.8 months-13 years] with a median pulmonary resistance to perfusion of 10.1 [2.1-37.7]. Wood-Units x m2 were studied. Diagnoses included PH due to congenital heart disease (AVSD n = 5; VSD n = 2; PDA n = 1) or unknown causes (n = 6). The ratios of pulmonary/systemic pressure (Pp/Ps) and of pulmonary/systemic resistance (Rp/Rs) were recorded a) at baseline, b) during oxygen (FiO2 = 1.0) and c) while on NO (80 ppm max., at FiO2 = 0.23). In 13 out of 14 children prostanoids were given additionally: 7 received prostacyclin (i.v.) and 6 were given iloprost which was nebulized. ET-1, cGMP and cAMP were measured in blood samples taken from the pulmonary vein or left ventricle at baseline, during increased FiO2, during NO inhalation and while on prostanoids. Pulmonary vasodilation in response to oxygen was found in 2/14 patients. 4/14 patients responded to NO and 2/7 to prostacyclin i.v. Increased FiO2 was not associated with changes in plasma concentrations of ET-1, cGMP or cAMP. NO inhalation was followed by an increase in cGMP levels from 10.9 [5.5-55.4] nM/L to 21.3 [6.4-76.3] nM/L independent from the individual hemodynamic response. Oxygen and NO identify most children with reactive pulmonary vasculature. cGMP plasma levels do not correlate with individual hemodynamic responses to NO.