Pregnancy alters hemodynamic responses to hemorrhage in conscious rabbits

Kathy A. Clow, George D. Giraud, Bryan E. Ogden, Virginia L. Brooks

Research output: Contribution to journalArticle

11 Scopus citations

Abstract

Pregnant animals are less able to maintain mean arterial pressure (MAP) during hemorrhage compared with nonpregnant animals, but the hemodynamic basis of this difference is unknown. The hypothesis that pregnancy attenuates responses of cardiac output, as well as total peripheral resistance (TPR) and femoral conductance, to hemorrhage was tested in conscious rabbits in both the pregnant and nonpregnant state (n = 10). During continuous slow blood loss (2% of the initial blood volume per minute), MAP was maintained initially in both groups. However, MAP then abruptly decreased to < 45 mmHg in all animals after a smaller percentage of the initial blood volume was removed in pregnant compared with nonpregnant rabbits (43.6 ± 1.7%, nonpregnant; 29.6 ± 2.2%, pregnant; P < 0.005). The more rapid transition to hypotension exhibited by pregnant rabbits was associated with greater initial falls in cardiac output (-56 ± 10 ml/min, nonpregnant; -216 ± 33 ml/min, pregnant; P < 0.005) and stroke volume (0.8 ± 0.1 ml/beat, nonpregnant; -1.3 ± 0.1 ml/beat, pregnant; P < 0.05): In addition, the increase in TPR as a function of the decrease in cardiac output was markedly attenuated (P < 0.0001) during pregnancy. Whereas femoral conductance decreased in nonpregnant rabbits, it did not change significantly in pregnant animals. In conclusion, the lesser ability of conscious pregnant rabbits to maintain MAP during hemorrhage is due largely to a greater decrease in cardiac output but also to inadequate reflex increases in TPR, possibly in part in the femoral vascular bed.

Original languageEnglish (US)
Pages (from-to)H1110-H1118
JournalAmerican Journal of Physiology - Heart and Circulatory Physiology
Volume284
Issue number4 53-4
DOIs
StatePublished - Apr 1 2003

Keywords

  • Cardiac output
  • Femoral conductance
  • Mean arterial pressure
  • Stroke volume
  • Total peripheral resistance

ASJC Scopus subject areas

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

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