ORGAN BLOOD-SUPPLY AND TISSUE OXYGENATION AFTER LIMITED NORMOVOLEMIC HEMODILUTION WITH 3-PERCENT VERSUS 6-PERCENT DEXTRAN-60

Background: The use of dextran solutions (DX) for hemodilution (HD) is considered being detrimental due to their effects on plasma viscosity . Methods: 14 splenectomized beagles (12.7 +/- 1.3 kg) were anesthetiz ed 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 (r adioisotope-labelled microspheres, empty set 15 mum), local tissue oxy genation (pO2 multiwire surface electrode), plasma and blood volume (I -131-labelled dog albumin distribution), and macrohemodynamics were ev aluated with regard to actual changes in hct and plasma viscosity, res pectively. Results: Normovolemic HD with either solution resulted in e quivalent changes in macrohemodynamics, and plasma and blood volume. D espite 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 org an blood flow as compared to 6% DX-60. In both groups, elevated pO2 va lues 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. Conclusion: 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 rheol ogical factors influencing oxygen delivery, hematocrit thus plays the predominant role, while plasma viscosity is of minor importance.