Hemodilution improves cerebral hemodynamics in internal carotid artery occlusion

Hemodilution may be a useful form of therapy for patients with carotid occlusive disease and hemodynamic ischemia. Accordingly, we evaluated the effects of hemodilution on cerebral hemodynamics and oxygen metabolism in patients with carotid artery occlusion.

Using positron emission tomography, we analyzed regional cerebral blood flow, oxygen extraction fraction, oxygen metabolic rate, and blood volume before and after isovolemic hemodilution in five patients with unilateral internal carotid artery occlusion and minor stroke. Hemodilution was accomplished by phlebotomy of 400 mL and infusion of 400 mL of hydroxyethyl starch.

Before hemodilution, the patients had a significant decrease in blood flow and oxygen transport along with significantly elevated oxygen extraction fraction in the cerebral hemisphere with carotid artery occlusion compared with six control subjects. After hemodilution, the hematocrit and arterial oxygen content decreased from 41.2% and 18.6 mL/dL to 36.3% and 16.5 mL/dL, respectively. Both cerebral blood flow and oxygen transport were increased and oxygen extraction fraction was decreased without any change in oxygen consumption. The degree of increase in blood flow and oxygen transport was positively correlated with the ratio of oxygen extraction fraction to blood volume before hemodilution.

These findings indicate that hemodilution improves oxygen transport as well as blood flow in patients with internal carotid occlusion and decreased perfusion and that this improvement may be more prominent in patients with a severely compromised hemodynamic state. Thus, hemodilution may be useful in patients with hemodynamic ischemia.