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Pulmonary clearance of norepinephrine in lambs
B A Chappell1, J F Padbury, D M Habib
1Department of Pediatrics, Harbor-UCLA Medical Center, Torrance 90509.
Pediatric Research
|January 1, 1991
Summary
Pulmonary clearance significantly removes norepinephrine in young lambs, accounting for over 70% of total body clearance. This clearance is reduced during hypoxia, potentially impacting pulmonary vascular resistance.
Area of Science:
- Cardiovascular Physiology
- Neonatal Metabolism
- Pulmonary Circulation
Background:
- The lungs are crucial for metabolizing vasoactive substances like endogenous amines.
- The specific role of pulmonary clearance of norepinephrine in newborn lambs remains unclear.
Purpose of the Study:
- To determine the in vivo pulmonary clearance and spillover rate of norepinephrine in young lambs.
- To investigate the impact of hypoxia on pulmonary norepinephrine clearance.
Main Methods:
- Utilized radiolabeled tracer norepinephrine in acutely instrumented lambs.
- Measured fractional extraction, pulmonary clearance rate, and net removal rate of norepinephrine.
- Assessed changes under baseline and hypoxic conditions.
Main Results:
- Baseline fractional extraction of norepinephrine was 23%, with a clearance rate of 61 mL/kg/min.
- Pulmonary clearance accounted for over 70% of whole-body norepinephrine clearance.
- Hypoxia significantly decreased fractional extraction (16%) and pulmonary clearance (31 mL/kg/min).
Conclusions:
- Pulmonary clearance is a major determinant of norepinephrine clearance in 1-week-old lambs.
- Reduced norepinephrine clearance during hypoxia may contribute to altered pulmonary vascular resistance in newborns.