Influence of a recombinant hemoglobin solution on blood rheology

Red cell transfusion is a matter of great concern because of viral infections. Recently, a genetically engineered hemoglobin, rHb 1.1, consisting of two alpha chains and one beta chain, has been developed; it has good oxygen-carrying and -unloading capacity and is devoid of renal toxicity.

An in vitro study of the influence of increasing concentrations of rHb 1.1 on plasma and blood viscosity, red cell aggregation and deformability, and neutrophil deformability was performed.

The rHb 1.1 (50 g/L in phosphate-buffered saline) had a viscosity of 0.80 +/- 0.02 mPa-sec at 37 degrees C, which was lower than that of normal Hb solution at the same Hb concentration (0.93 +/- 0.01 mPa-sec, p < 0.001) or of albumin, a protein with similar molecular weight (0.93 +/- 0.01, p < 0.0001). The admixture of rHb 1.1 to plasma or to red cell suspensions, at constant Hb concentration, led to a dose-dependent decrease in their viscosities. The simulation of replacement therapy during blood loss revealed rheologic properties of rHb 1.1 that were superior to those of all other fluids. The rHb 1.1 did not affect red cell aggregation or the deformability of red cells or white cells, as measured by the cells' transit time through small pores.

These data indicate that rHb 1.1 has excellent rheologic properties and should hold promise not only as an oxygen-carrying therapeutic agent, but probably also as a hemodilutional agent that simultaneously decreases blood viscosity and provides oxygen-carrying capacity.