Early deleterious hemorheologic changes following acute experimental coronary occlusion and salutary antihyperviscosity effect of hemodilution with stroma-free hemoglobin.

Viscometric measurements were made on the blood of anesthetized dogs before and following acute occlusion of the left anterior descending coronary artery. Within an hour of the occlusion, the low-shear viscosity of whole blood was significantly increased and continued to rise thereafter. This was accompanied by significant increments in the yield-shear stress of whole blood, suggesting accelerated tendencies in aggregation and plasma viscosity. In another group of dogs, 1 hour after coronary occlusion, rapid isovolemic hemodilution was performed with an 8% solution of stroma-free hemoglobin, reducing the hematocrit to 24%. This was followed by marked reduction of whole blood viscosity at all shear rates, abolition of the yield-shear stress, and reduction of plasma viscosity. These findings suggest that a hyperviscosity state develops early in acute myocardial ischemia which is detrimental to collateral perfusion of the marginal zone of ischemic myocardium. Such hyperviscosity syndrome can be blocked by hemodilution with stroma-free hemoglobin.