Divergent effects of ephedrine and phenylephrine on cardiovascular hemodynamics of near-term fetal sheep exposed to hypoxemia and maternal hypotension

T. Erkinaro, K. Mäkikallio, G. Acharya, M. Päkkilä, T. Kavasmaa, J. C. Huhta, S. Alahuhta, J. Räsänen

Research output: Contribution to journalArticle

20 Scopus citations

Abstract

Background: We hypothesized that the administration of ephedrine and phenylephrine for maternal hypotension modifies cardiovascular hemodynamics in near-term sheep fetuses. Methods: At 115-136 days of gestation, chronically instrumented, anesthetized ewes with either normal placental function or increased placental vascular resistance after placental embolization were randomized to receive boluses of ephedrine (n = 12) or phenylephrine (n = 12) for epidural-induced hypotension after a short period of hypoxemia. Fetal cardiovascular hemodynamics were assessed by Doppler ultrasonography at baseline, during hypotension and after vasopressor treatment. Results: During hypotension, fetal PO2 decreased and proximal branch pulmonary arterial and pulmonary venous vascular impedances increased. Additionally, in the embolized fetuses, the time-velocity integral ratio between the antegrade and retrograde blood flow components of the aortic isthmus decreased. These parameters were restored to baseline conditions by ephedrine but not by phenylephrine. With phenylephrine, weight-indexed left ventricular cardiac output and ejection force decreased in the non-embolized fetuses, and the proportion of isovolumetric contraction time of the total cardiac cycle was elevated in the embolized fetuses. Conclusions: After exposure to hypoxemia and maternal hypotension, ephedrine restored all fetal cardiovascular hemodynamic parameters to baseline. Phenylephrine did not reverse fetal pulmonary vasoconstriction or the relative decrease in the net forward flow through the aortic isthmus observed in fetuses with increased placental vascular resistance. Moreover, fetal left ventricular function was impaired during phenylephrine administration.

Original languageEnglish (US)
Pages (from-to)922-928
Number of pages7
JournalActa Anaesthesiologica Scandinavica
Volume51
Issue number7
DOIs
StatePublished - Aug 1 2007

Keywords

  • Anesthesia
  • Anesthetic techniques
  • Doppler ultrasonography
  • Ephedrine
  • Epidural
  • Measurement techniques
  • Obstetric
  • Phenylephrine
  • Sympathetic nervous system

ASJC Scopus subject areas

  • Anesthesiology and Pain Medicine

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