Abstract
A marked increase in plasma catecholamines (CAT) at birth has been described in animals and man. This study was conducted to determine whether the magnitude and duration of the CAT surge are similar in preterm (130 days, n=4) and term lambs (145 days, n=6), and to correlate plasma CAT and plasma END levels in the acutely exteriorized fetal lamb. CAT were measured by radioenzymatic assay and END by specific radioimmunoassay. Preterm lambs were maintained physiologically stable by administration of natural sheep surfactant intratracheally prior to the first breath. Baseline CAT & END were similar in the term and preterm lambs. Following umbilical cord cutting there was a marked increase in circulating norepinephrine (NE) and epinephrine (E) levels. Peak preterm NE (2.2±0.6 ng/ml at 1 hr) was greater than peak term NE (1.0±0.2 ng/ml, at 5 min). Peak preterm E also later and greater than peak term E (2.9±0.9 ng/ml at 1 hr vs 0.9±0.2 ng/ml at 15 min, respectively p<.01). Similarly, peak plasma END in preterm animals (2.2±0.1 ng/ml at 3 hrs) was later and greater than at term (1.1±0.2 ng/ml at 15 min). END was positively correlated with NE and E in both term and preterm animals (p<.05).
Conclusions: 1) Preterm animals have a delayed, exaggerated CAT surge following delivery, 2) The peak plasma END response parallels the peak of plasma CAT. Speculation: The CAT surge at birth is an important adaptive phenomenon and may be modulated by changes in the END system.
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Padbury, J., Ogata, Y., Wang, D. et al. 299 NEONATAL ADAPTATION: SYMPATHOADRENAL AND ENDORPHIN (END) RESPONSES TO DELIVERY IN TERM AND PRETERM LAMBS. Pediatr Res 19, 160 (1985). https://doi.org/10.1203/00006450-198504000-00329
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DOI: https://doi.org/10.1203/00006450-198504000-00329