Effects of major abdominal operations on human blood rheology.

Serial blood rheological measurements were systematically carried out in 14 patients undergoing major elective abdominal operations for a period up to 10 days after operation. The measurements included blood viscosity over a wide range of shear rates (0.01 to 208 sec.-minus 1), hematological data, and plasma protein concentrations. Significantly elevated plasma viscosity preoperatively accounted for a normal blood viscosity in the presence of anemia. After an initial drop due to hemodilution lasting for 1 to 3 days after operation, blood viscosity returned to normal by the tenth postoperative day. This was the result of an increased plasma viscosity, primarily due to rise in plasma fibrinogen and alpha2- and beta2-globulin concentrations. The red cell deformability of these patients was normal except for one patient who received seven units of transfused blood. The results of this investigation suggest that abnormal rheological properties of blood and plasma should be considered in therapeutic attempts to improve microcirculatory flow and oxygen delivery to tissues.