Dynamics of cardiovascular responses to repeated partial umbilical cord compression in late-gestation sheep fetus

Dino A. Giussani, Nobuya Unno, Susan L. Jenkins, Richard A. Wentworth, Jan B. Berks, Jason H. Collins, Peter W. Nathanielsz

Research output: Contribution to journalArticlepeer-review

51 Scopus citations

Abstract

We characterized the detailed hemodynamics of fetal blood pressure, heart rate, common umbilical blood flow, and femoral blood flow responses to partial compression of the umbilical cord and tested the hypothesis that repeated cord compression modulates fetal cardiovascular responses in 10 chronically instrumented fetal sheep at ~130 days of gestation. In five fetuses (group I), partial compression of the umbilical cord was induced 12 times, each for 5 min at 15-min intervals. Each cord compression reduced common umbilical blood flow by 50% and produced modest falls in fetal pH (7.33 ± 0 to 7.29 ± 0) and arterial Po2 (21.1 ± 0.2 to 16.8 ± 0.2 mmHg) and a mild increase in arterial PCO2 (49.9 ± 0.5 to 54.9 ± 0.4 mmHg). Sham experiments were performed in five other fetuses (group II). Second-by- second analysis of group I fetal cardiovascular data revealed a clear biphasic response to partial cord compression. Phase 1 (1st min of cord compression) was characterized by a rapid bradycardia and a rapid femoral vasoconstriction (primary response); phase H (minutes 2-5 of cord compression) was characterized by a delayed bradycardia and a return of femoral vascular resistance toward baseline (secondary response). Repeated cord compression abolished the primary, but not the secondary, cardiovascular responses. These results demonstrate that fetal cardiovascular responses to stress may be modified by preexposure to repeated intrauterine challenges.

Original languageEnglish (US)
Pages (from-to)H2351-H2360
JournalAmerican Journal of Physiology - Heart and Circulatory Physiology
Volume273
Issue number5 42-5
DOIs
StatePublished - 1997
Externally publishedYes

Keywords

  • Biphasic response
  • Cord occlusion
  • Hypoxia
  • Mechanoreflex

ASJC Scopus subject areas

  • Physiology
  • Cardiology and Cardiovascular Medicine
  • Physiology (medical)

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