Improvement in blood flow through a critical arterial stenosis by defibrination with ancrod

Using electromagnetic flow probes, cardiac output and hind limb blood flow were measured in dogs in which one hind limb had been rendered ischemic. Four dogs served as controls; seven were defibrinated by intravenous infusion of ancrod, 1 unit/kg, over a 30-minute period. In both groups, hematocrit readings remained constant, but cardiac output fell (this was attributed to barbiturate anesthesia), as did flow in the normal hind limb. In the controls after three hours, flow in the ischemic hind limb had decreased by 34%, but in the treated animals it had increased by 20%. The difference was statistically significant (P less than .001). The selective increase in blood flow in the ischemic limb may be explained by the greater reduction in blood viscosity at low shear rates achieved by defibrination.