Effect of hemorrhage rate on early hemodynamic responses in conscious sheep

Christopher G. Scully, Chathuri Daluwatte, Nicole R. Marques, Muzna Khan, Michael Salter, Jordan Wolf, Christina Nelson, John Salsbury, Perenlei Enkhbaatar, Michael Kinsky, George C. Kramer, David G. Strauss

Research output: Contribution to journalArticlepeer-review

19 Scopus citations


Physiological compensatory mechanisms can mask the extent of hemorrhage in conscious mammals, which can be further complicated by individual tolerance and variations in hemorrhage onset and duration. We assessed the effect of hemorrhage rate on tolerance and early physiologic responses to hemorrhage in conscious sheep. Eight Merino ewes (37.4±1.1 kg) were subjected to fast (1.25 mL/kg/min) and slow (0.25 mL/kg/min) hemorrhages separated by at least 3days. Blood was withdrawn until a drop in mean arterial pressure (MAP) of >30mmHg and returned at the end of the experiment. Continuous monitoring included MAP, central venous pressure, pulmonary artery pressure, pulse oximetry, and tissue oximetry. Cardiac output by thermodilution and arterial blood samples were also measured. The effects of fast versus slow hemorrhage rates were compared for total volume of blood removed and stoppage time (when MAP<30mmHg of baseline) and physiological responses during and after the hemorrhage. Estimated blood volume removed when MAP dropped 30 mmHg was 27.0±4.2% (mean±standard error) in the slow and 27.3±3.2% in the fast hemorrhage (P=0.47, paired t test between rates). Pressure and tissue oximetry responses were similar between hemorrhage rates. Heart rate increased at earlier levels of blood loss during the fast hemorrhage, but hemorrhage rate was not a significant factor for individual hemorrhage tolerance or hemodynamic responses. In 5/16 hemorrhages MAP stopping criteria was reached with <25% of blood volume removed. This study presents the physiological responses leading up to a significant drop in blood pressure in a large conscious animal model and how they are altered by the rate of hemorrhage.

Original languageEnglish (US)
Pages (from-to)1-15
Number of pages15
JournalPhysiological reports
Issue number7
StatePublished - Apr 1 2016


  • Hemodynamic compensation
  • Hemorrhage
  • Hypovolemia

ASJC Scopus subject areas

  • Physiology
  • Physiology (medical)


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