Blood viscosity and red cell aggregation changes after hemodilution in vivo and in vitro

Abstract

The viscosity of whole blood (WB), plasma (P), and packed cells (PC) was measured in a Wells-Brookfield cone plate viscometer on blood from dogs undergoing surgical shock and hemodilution with different plasma substitutes and on human ACD-blood diluted in vitro to comparable concentrations of colloids. Erythrocyte sedimentation rate (ESR) and microscopic red cell aggregate count were used as in vitro indices of red cell aggregation. During three hours of intestinal shock WB viscosity increased by 20 %, hematocrit increased from 50.9 to 59. 1 %, P viscosity was unchanged and PC viscosity increased by 6 %. When compared at equal hematocrit drop, Ringer’s acetate decreased WB viscosity more than albumin, ACD-plasma, dextran 70 and gelatin in this order both on blood diluted in vitro and in vivo. Since the duration of volume expansion in vivo after Ringer’s solution was very transient the absolute decrease of viscosity was less than that observed after all other solutions except gelatin. P viscosity increased with dextran 70, was unchanged with ACD-plasma, dextran 40, and gelatin and decreased with albumin and Ringer’s acetate dilution. A marked red cell aggregation occurred with dextran 70 and gelatin with increasing concentration. No aggregation of red cells was seen with dextran 40, albumin, or Ringer’s acetate. It is concluded that lasting hemodilution in vivo is best achieved with albumin and dextran 40 based on their viscosity influences, volume expansion duration and their lack of red cell aggregation properties.