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Effects of hemodilution on skin microcirculation
S Mirhashemi1, G A Breit, R H Chavez Chavez
1Department of Applied Mechanics and Engineering Sciences, University of California, San Diego, La Jolla 92093.
The American Journal of Physiology
|March 1, 1988
Summary
Normovolemic hemodilution increased capillary red blood cell (RBC) velocity and decreased capillary hematocrit (Hctcap) without altering RBC flux or arteriolar diameter in hamsters. Systemic parameters normalized as hematocrit recovered.
Area of Science:
- Physiology
- Microcirculation Research
- Hemodynamics
Background:
- Understanding microcirculatory responses to hemodilution is crucial for managing conditions involving altered blood viscosity.
- Normovolemic hemodilution is a technique used to reduce blood viscosity and improve flow.
- Previous studies have not fully elucidated the specific microvascular adaptations during progressive hemodilution.
Purpose of the Study:
- To investigate the effects of normovolemic hemodilution on red blood cell (RBC) velocity, capillary hematocrit (Hctcap), RBC flux, and arteriolar diameter in the hamster skinfold preparation.
- To assess the immediate and short-term recovery responses of microcirculatory parameters following hemodilution.
Main Methods:
- Experiments were conducted in unanesthetized Syrian hamsters using the skinfold window preparation.
- Successive normovolemic hemodilutions were performed using 6% Dextran 70.
- Systemic arterial pressure, heart rate, and systemic hematocrit were continuously monitored.
- Capillary RBC velocity, Hctcap, RBC flux, and arteriolar diameter were measured at various levels of hemodilution.
Main Results:
- Red blood cell flux remained unchanged up to 50% hemodilution (systemic hematocrit 25% ± 4).
- Capillary RBC velocity significantly increased by 60%, while Hctcap significantly decreased by 30%.
- Arteriolar diameter showed no significant change during hemodilution; systemic parameters recovered proportionally with hematocrit reestablishment.
Conclusions:
- Normovolemic hemodilution primarily alters capillary RBC velocity and Hctcap, rather than RBC flux or arteriolar diameter, in this microcirculation model.
- The microvasculature demonstrates adaptive changes in RBC distribution and velocity to maintain flow during reduced systemic hematocrit.
- These findings provide insights into the compensatory mechanisms within the microcirculation during hemodilution and potential therapeutic implications.