PRETERM OVINE CATECHOLAMINE RESPONSE TO UMBILICAL CORD CUTTING

Abstract

Catecholamine (CAT) release has been observed in the near term ovine fetus in response to a number of provocative stimuli. Previously we reported the effects of intrauterine manipulation, fetal exteriorization, and umbilical cord cutting (UCC) on CAT and free fatty acid (FFA) levels in the blood of near term lambs. In the present study we repeat these measurements in premature (m G.A.=132 d, n=5) lambs. Following fetal arterial catheterization lambs were exteriorized and maintained with an intact umbilical circulation. Following UCC the animals were treated with intratracheal surfactant and placed on ventilators for support. This allowed us to maintain the animals with normal blood gases throughout the experiment. Results show that instrumentation and delivery evoked a brief elevation of fetal CAT levels which returned to baseline within 30 min. UCC was followed by a marked increase in epinephrine (E) and norepinephrine (NE) (mean peak plasma levels of 10,000 pg/ml and 3,700 pg/ml). These results were compared with data in near term lambs by two-way ANOVA; the preterm CAT peaks are higher and reached later in preterm animals (p<0.001). The FFA response of the preterm animals was blunted when compared with the response of the near term animals (p< 0.001). Conclusions: 1) UCC is an important stimulus for fetal CAT release in preterm as well as term animals. 2) The peak CAT levels in preterm animals are much higher and reached later after UCC than in term animals. Speculation: Augmented CAT release in the preterm animal is an important adaptive phenomenon.

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