Acute hemoconcentration during psychological stress: assessment of hemorheologic factors.

In this study, we examined the effects of acute psychological stress on hemorheology and hemoconcentration in humans and the associations between stress-induced cardiovascular reactivity and hemorheological changes. Stress-induced changes in hemorheology and hemorheological changes were assessed by measuring plasma viscosity, calculated plasma volume, and total plasma protein. Cardiovascular, hemorheologic, and hematologic variables were assessed in 29 healthy men during a 30-min baseline period and a 5-min speech task. Results indicated that the speech task produced a significant increase in plasma viscosity and total plasma protein and a significant decrease in calculated plasma volume. Significant correlations were observed between changes in blood pressure and heart rate and changes in plasma viscosity, total plasma protein, and calculated plasma volume. These results provide direct evidence that acute psychological stress can produce significant changes in hemorheology and hemoconcentration. The most likely mechanism for the stress-induced hemoconcentration effect is a fluid shift from the vascular to the interstitial spaces through increased blood pressure.