Relation between blood viscosity and hematocrit in rabbits subjected to repeated treatment with endotoxin

Blood rheology was studied in rabbits repeatedly treated with endotoxin at a dose of 0.1 mg administered 3 times, at intervals of 3 days. On the 7th day after the last endotoxin injection, blood was sampled 3 times from the femoral artery under anesthesia using pentobarbital sodium. Blood viscosity was determined at a shear rate of 150 s-1 at 37 degrees C using a cone-plate viscometer. Plasma fluidity was determined using the filtration method. Hematocrit and whole blood viscosity showed no significant differences between the untreated rabbits (Group A) and rabbits treated with endotoxin (Group B). Plasma fluidity was significantly lowered in Group B. Whole blood viscosity correlated well with hematocrit in Group A, but there was no correlation in Group B. The ratio of hematocrit to whole blood viscosity, which is considered to be the index of oxygen delivery from the blood rheological point of view, indicated no significant difference between the two groups. The optimal hematocrit to oxygen delivery, however, was higher in Group B than in Group A. These data suggest that the high hematocrit rather becomes an advantage to oxygen delivery in endotoxicosis because the hematocrit-viscosity relation is disturbed.