The variability of blood pressure due to small changes of hematocrit.
The hematocrit (Hct) of awake hamsters was lowered to 90% of baseline by isovolemic hemodilution using hamster plasma to determine the acute effect of small changes in Hct and blood viscosity on systemic hemodynamics. Mean arterial blood pressure increased, reaching a maximum of about 10% above baseline (8.6 +/- 5.5 mmHg) when Hct decreased 8.4 +/- 1.9% (P < 0.005). Cardiac output increased continuously with hemodilution. These conditions were reached at approximately 60 min after exchange transfusion and remained stationary for 1 h. Peripheral vascular resistance was approximately constant up to a decrease of Hct of about 10% and then fell continuously with lowering Hct. Vascular hindrance or vascular resistance independent of blood viscosity increased by about 20% and remained at this level up to an Hct decrease of 20%, indicating that the vasculature constricted with the lowered Hct. The results for the initial 2-h period are opposite but continuous with previous findings with small increases in Hct. In conclusion, limited acute anemic conditions increase mean arterial blood pressure during the initial period of 2 h, an effect that is quantitatively similar but opposite to the acute increase of Hct during the same period.
Vázquez
Beatriz Y Salazar
BY
Faculty of Medicine, Universidad Juárez del Estado de Durango, Victoria de Durango, Durango, Mexico.
Martini
Judith
J
Tsai
Amy G
AG
Johnson
Paul C
PC
Cabrales
Pedro
P
Intaglietta
Marcos
M
D000740:Anemia / Q000503:physiopathology*; D000818:Animals; D001794:Blood Pressure / Q000502:physiology*; D001809:Blood Viscosity / Q000502:physiology; D001810:Blood Volume / Q000502:physiology; D006224:Cricetinae; D006400:Hematocrit; D006438:Hemodilution; D006439:Hemodynamics / Q000502:physiology*; D008647:Mesocricetus