Effects of Hemodilution on Peripheral Circulation

Abstract

In 7 anesthetized dogs the authors produced anemia by exchanging isovo lemic blood with plasma substitute and thus reducing hemoglobin gradually from 17.9 ± 0.7 to 8.5 ± 0.7 gr/dL in three steps. Samples were taken from pe ripheral blood at the animals' normal hemoglobin and at different degrees of hemodilution for the determination of Hb, viscosity, fibrinogen, venous blood lactate and pyruvate, pH, pO₂, and oxygen saturation, while cardiac output, heart rate, and aortic pressure were measured. Total peripheral resistance, oxy gen content, and oxygen transport were calculated. Progressive hemodilution resulted in a significant increase in cardiac output from 2.5±0.1 to 4.2±0.2 L/min (p < 0.001), while peripheral resistance decreased clearly parallel with the whole blood viscosity (from 2.2±0.1 to 1.2±0.1 mm Hg/mL/sec, p < 0.001). The value of arterial oxygen content was decreased from 22.6±1.1 to 10.1 ±0.7 mL/dL of blood (p < 0.001), but the systemic oxygen transport was completely compensated at hemodilution step A, and moderately at steps B and C, because of the increased cardiac output. Oxygen consumption was slightly decreased, while aortic pressure, pH, pO₂, and oxygen saturation did not change. These data support the concept that moderate normovolemic hemodilution improves the peripheral circulation and does not jeopardize tissue oxygenation.