Rheological Aspects of Experimental Hypervolemic Hemodilution with Low Molecular Weight Dextran: Relationships of Cortical Blood Flow, Cardiac Output, and Intracranial Pressure to Fresh Blood Viscosity and Plasma Volume

Publisher Website
Google Scholar
Abstract
Significant rheological, cerebrovascular, and cardiovascular alterations from base line conditions in splenectomized dogs were observed after serial intravascular volume expansion with low molecular weight dextran (MW 40,000). Nine dogs received two infusions of dextran within 120 minutes; each infusion equaled 20% of the respective dog's total blood volume (TBV). The plasma volume (PV) increased 48% and then another 40% after the two respective infusions, while the hematocrit (Hct) was obligatorily reduced by 20% and the 9%. The relative fresh blood viscosity at the shear rate of 10 sec−1 decreased initially 27% and then 6%. The blood viscosity correlated inversely with TBV and PV and varied directly with Hct after these dextran infusions. After two respective dextran infusions, cardiac output (CO) increased initially 43% and then 26% without significant alterations in mean arterial blood pressure. In addition, CO correlated negatively with both Hct and blood viscosity. Although the 14% elevation in regional cortical blood flow (rCoBF) in the territory of the middle cerebral artery did not reach statistical significance, rCoBF correlated inversely with both Hct and blood viscosity and was related directly to TBV, PV, and CO after the dextran infusions. Cortical vascular resistance (CVR) decreased initially 6% and then 5% after the two respective dextran infusions. The CVR was related inversely to PV, but its correlation with blood viscosity did not reach statistical significance. Intracranial pressure (ICP) rose 2-fold; correlated positively with TBV, PV, and rCoBF; and varied inversely with CVR. Our data suggest that hypervolemic hemodilution with expansion of PV significantly reduces blood viscosity at relatively low shear rates. Fresh blood viscosity seems to be a major factor determining CO and cerebral perfusion after the administration of low molecular weight dextran. Reductions in blood viscosity may account for the direct relationship between rCoBF and CO observed after intravascular volume expansion with hemodiluting agents. Hypervolemic hemodilution with dextran raises ICP, possibly as a function of increased cerebral blood volume resulting from the reduced CVR and the elevated PV.

This publication has 0 references indexed in Scilit: