Reversible changes in norepinephrine extraction by the lungs in children with pulmonary hypertension.

Extraction of circulating vasoactive hormones by the lung may influence systemic vasomotor tone. Since this process occurs in the pulmonary microcirculation, we evaluated the effects of pulmonary artery hypertension (PAH) secondary to congenital heart disease (CHD) on this metabolic function of lung. Eleven patients with varying congenital cardiac lesions were studied preoperatively and postoperatively. Five had normal pulmonary artery pressure (PAP) (group I), and six had PAH with peak systolic PAP greater than 40 mm Hg (group II). PA and postpulmonary arterial blood samples were collected before and after surgery at the time of pressure measurements. Norepinephrine (NE) and epinephrine (EPI) levels were determined by radioenzymatic assay. Preoperatively, circulating NE levels were higher (P less than 0.05) and NE extraction measured was lower (P less than 0.01) in group II patients as compared with group I. Extraction increased in group II postoperatively after PA pressures were reduced, becoming equivalent to group I postoperative values. EPI extraction was negligible in either group at any time. These data demonstrate that lungs of children are capable of selective catecholamine uptake and that elevated PAP occuring with CHD is associated with a decrease in this capability and an increase in circulating NE levels. Additionally, the decrease in NE extraction observed with PAH is reversible once PAP is reduced by surgical repair of the cardiac defect.