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Integrated Compensatory Responses in a Human Model of Hemorrhage
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Systemic and microcirculatory responses to progressive hemorrhage.

Arnaldo Dubin1, Mario Omar Pozo, Gonzalo Ferrara

  • 1Facultad de Ciencias Médicas, Cátedra de Farmacología Aplicada, Universidad Nacional de La Plata, La Plata, Argentina. arnaldodubin@speedy.com.ar

Intensive Care Medicine
|January 8, 2009
PubMed
Summary

Progressive hemorrhage rapidly impairs microcirculation and increases lactate, even before systemic blood pressure drops. These early microcirculatory changes in the gut and sublingual areas signal the first signs of shock.

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Area of Science:

  • Physiology
  • Hemodynamics
  • Microcirculation

Background:

  • Hemorrhage triggers complex physiological responses.
  • Understanding the interplay between systemic and microcirculatory changes is crucial for managing shock.
  • Early indicators of circulatory compromise are vital for timely intervention.

Purpose of the Study:

  • To compare systemic hemodynamic changes with microcirculatory alterations in various vascular beds during progressive hemorrhage.
  • To identify the earliest indicators of circulatory distress following blood loss.

Main Methods:

  • Anesthetized, mechanically ventilated sheep underwent stepwise hemorrhage (15 ml/kg total).
  • Systemic hemodynamics (cardiac output, blood pressure) and microcirculatory parameters (flow index, red blood cell velocity) in the sublingual and intestinal regions were monitored.
  • Arterial blood gases, lactate, and oxygen transport/consumption were measured.

Main Results:

  • Progressive bleeding reduced cardiac output, mesenteric blood flow, and oxygen transport from the initial bleeding stage.
  • Systemic and intestinal oxygen consumption remained unchanged initially.
  • Mean arterial blood pressure and pH were affected only in the final bleeding stage.
  • Arterial lactate increased, while sublingual and intestinal microcirculatory flow and velocity decreased after the first bleeding step.

Conclusions:

  • Early microcirculatory dysfunction in the gut and sublingual areas, along with elevated arterial lactate, occurs simultaneously with the first stage of bleeding.
  • These microcirculatory changes can be detected using flow index or red blood cell velocity measurements.
  • Microcirculatory alterations precede significant systemic hemodynamic deterioration during hemorrhage.