Organ blood supply and tissue oxygenation after limited normovolemic hemodilution with 3% versus 6% Dextran-60

The use of dextran solutions (DX) for hemodilution (HD) is considered being detrimental due to their effects on plasma viscosity.

14 splenectomized beagles (12.7 +/- 1.3 kg) were anesthetized and randomly assigned to HD to 20 vol% hematocrit (hct) with either 3 or 6% DX-60. The effects of HD upon nutritional organ blood flow (radioisotope-labelled microspheres, phi 15 microns), local tissue oxygenation (pO2 multiwire surface electrode), plasma and blood volume (131I-labelled dog albumin distribution), and macrohemodynamics were evaluated with regard to actual changes in hct and plasma viscosity, respectively.

Normovolemic HD with either solution resulted in equivalent changes in macrohemodynamics, and plasma and blood volume. Despite the increase in plasma viscosity associated with HD using 6% DX-60 (up to 1.45 +/- 0.10 mPa.s), blood flow rose in all organs studied (p < 0.05). After HD by means of 3% DX-60, plasma viscosity remained unchanged (1.09 +/- 0.04 mPa.s) but was not associated with higher organ blood flow as compared to 6% DX-60. In both groups, elevated pO2 values on the surface of liver and skeletal muscle (p < 0.01) as well as the shift in the pO2 histograms toward higher pO2 values indicated a more homogeneous tissue perfusion upon HD, independent of the diluent applied.

In comparison to 6% DX-60, the solution of 3% DX-60 is of equivalent efficacy as volume substitute and in the induction of normovolemic HD. The main advantage of 3% DX-60 solution, however, is the fact that twice as much volume can be administered before the recommended maximal daily dose of 1.5 g/kg DX is reached. Of the rheological factors influencing oxygen delivery, hematocrit thus plays the predominant role, while plasma viscosity is of minor importance.