Acute hemoconcentration during psychological stress: Assessment of hemorheologic factors

In this study, we examined the effects of acute psychological stress on hem orheology and hemoconcentration in humans and the associations between stre ss-induced cardiovascular reactivity and hemorheological changes. Stress-in duced changes in hemorheology and hemoconcentration were assessed by measur ing plasma viscosity, calculated plasma volume, and total plasma protein. C ardiovascular, hemorheologic, and hematologic variables were assessed in 29 healthy men during a 30-min baseline period and a 5-min speech task. Resul ts indicated that the speech task produced a significant increase in plasma viscosity and total plasma protein and a significant decrease in calculate d 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 eviden ce that acute psychological stress can produce significant changes in hemor heology and hemoconcentration The most likely mechanism for the stress-indu ced hemoconcentration effect is a fluid shift from the vascular to the inte rstitial spaces through increased blood pressure.