Cardiovascular and hemorheological effects of three modified human hemoglobin solutions in hemodiluted rabbits

The cardiovasculareffects of human albumin (Alb) and three human hemoglobin(Hb) solutions, dextran-benzene-tetracarboxylate Hb,-crosslinked Hb, ando-raffinose-polymerized Hb werecompared in anesthetized rabbits undergoing acute isovolemichemodilution with Hct reduction from 41.4 ± 2.7 to 28.8 ± 1.6%. The impact of the vasoconstricting properties of Hb was examinedby measuring heart rate (HR), mean arterial pressure (MAP), abdominalaortic, and femoral arterial blood flow, vascular resistance (VR), and aortic distension during the first 3 h after hemodilution. The impactof the hemorheological parameters was assessed by measurements ofhemodiluted blood viscosity. In contrast to Alb, the Hb solutions elicited an immediate increase in MAP (20-38%). The effects of Alb and Hb solutions on HR, as well as on aortic and femoral arterial blood flow, were similar. VR decreased with Alb (20-28%) andincreased with all three Hb solutions (30-90%), but the MAP andVR rising trends were different with each Hb solution. Aorticdistension decreased in Hb groups compared with the Alb group for thefirst 60 min. The viscosity of hemodiluted blood was similar for all groups at high shear rates but was dependent on the viscosity of thesolutions at low shear rates. We conclude that the vasoconstriction elicited by the Hb solutions overrides the vasodilation associated withviscosity changes due to hemodilution and would be the major factorresponsible to the cardiovascular changes.