Rheological behaviour of red blood cells suspended in hemoglobin solutions. In vitro study comparing dextran-benzene-tetra-carboxylate hemoglobin, stroma free hemoglobin and plasma expanders

Circulating volume expansion for intentional hemodilution and/or resuscitat ion of hemorrhagic shock can be performed with hemoglobin-based oxygen carr iers (HBOC) which, in addition to oxygen transport, have vasoactive effects through poorly documented mechanisms. Among these, the effects of HBOC on red blood cell (RBC) rheology are relatively unknown. The aim of the presen t in vitro study was to measure the rheological effects of human hemoglobin bound to benzene-tetracarboxylate substituted dextran (Dex-BTTC-Hb) as an example of chemically modified hemoglobin. The viscosity was assessed with a capillary and a rotational viscometer for shear rates of 0.5-128 s(-1). E rythrocyte aggregation was determined by analysis of the red light backscat tered in a RBC suspension and with a rheoscope. The deformability was deter mined by the pressure-flow relationship of the RBC suspensions passed throu gh polycarbonate filters. At hematocrit of 0.35 1/1 and at low shear rates, the viscosity of RBC was higher in the presence of Dex-BTC-Hb as compared to free Hb, Dex-BTC, Dextran 40 (Plasmacair (R)), modified fluid gelatin (M FG-Plasmion (R)) or hydroxyethyl starch (HEA-Elohes (R)). The effect on ery throcyte aggregation of Dex-BTC-Hb was greater than that of standard soluti ons, but close to that of MFG or HEA. There was no apparent change in RBC d eformability. Dex-BTC-Hb, unlike free Hb, has a hyperaggregating effect on RBC, similar to that of some clinically used volume expanders. This hyperag gregating effect could influence the in vivo rheological behavior of substi tuted Hb by increasing shear stress. (C) 1999 Elsevier Science Ltd. All rig hts reserved.