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Reversible changes in norepinephrine extraction by the lungs in children with pulmonary hypertension
Insights
Pulmonary artery hypertension in children with congenital heart disease impairs the lung's ability to extract norepinephrine. This impaired extraction is reversible after surgical correction of the heart defect.
Area of Science:
- Cardiovascular Physiology
- Pulmonary Medicine
- Pediatric Cardiology
Background:
- The lung's pulmonary microcirculation metabolizes vasoactive hormones, influencing systemic vasomotor tone.
- Congenital heart disease (CHD) can lead to pulmonary artery hypertension (PAH), potentially affecting lung metabolic functions.
Purpose of the Study:
- To investigate the impact of PAH secondary to CHD on the lung's extraction of vasoactive hormones, specifically norepinephrine (NE) and epinephrine (EPI).
- To assess the reversibility of these effects after surgical intervention for CHD.
Main Methods:
- Studied 11 pediatric patients with CHD, divided into normal pulmonary artery pressure (PAP) and PAH groups.
- Collected pre- and post-operative blood samples from the pulmonary artery and aorta.
- Measured NE and EPI levels using radioenzymatic assay.
Main Results:
- Preoperatively, PAH patients exhibited higher circulating NE levels and lower NE extraction compared to controls.
- EPI extraction was negligible in all groups.
- Postoperatively, NE extraction improved in PAH patients after PAP reduction, reaching levels comparable to controls.
Conclusions:
- The pediatric lung selectively extracts catecholamines.
- Elevated PAP in CHD is associated with reduced NE extraction and increased circulating NE.
- Surgical repair of CHD improves NE extraction, indicating the reversibility of PAH-induced metabolic dysfunction.
Abstract:
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.