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Hemodynamic functions and blood viscosity in surface hypothermia
The American Journal of Physiology
|August 1, 1978
Summary
Hypothermia significantly increases blood viscosity due to low temperature, hemoconcentration, and low-flow states. This elevates systemic and pulmonary flow resistance, though cardiac output remains adequate.
Area of Science:
- Physiology
- Cardiovascular Research
Background:
- Hypothermia affects physiological functions.
- Understanding hemodynamic changes during hypothermia is crucial.
Purpose of the Study:
- To investigate hemodynamic functions and blood viscosity changes in dogs during hypothermia.
- To determine the factors contributing to increased blood viscosity and flow resistance.
Main Methods:
- Surface cooling of 14 pentobarbital-anesthetized dogs to a core temperature of approximately 25°C.
- Measurement of blood viscosity, plasma viscosity, hemoconcentration, systemic flow resistance, and pulmonary flow resistance.
- Monitoring of mixed venous oxygen saturation.
Main Results:
- Blood viscosity increased to 173% of normal at 25°C, driven by low temperature, hemoconcentration, and a low-flow state.
- Systemic flow resistance increased to 271% of control, equally influenced by blood viscosity and vascular hindrance.
- Pulmonary flow resistance was also significantly increased by blood viscosity.
Conclusions:
- The low-flow state significantly contributes to increased blood viscosity during hypothermia.
- Elevated blood viscosity and vascular hindrance are key factors in increased systemic and pulmonary resistance.
- Cardiac output appears adequate to meet metabolic demands in hypothermia based on mixed venous oxygen saturation.
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