Influence of hemodynamics on cerebral autoregulation in acute stroke measured by TCD

Aim: We treated 24 patients suffering from an acute ischemic stroke of the middle cerebral artery, with a hypervolemic hemodilution combined with dopamine/dobutamine. Method: The influence of blood pressure and cardiac output on the blood flow velocity in the middle cerebral artery was measured using transcranial Doppler sonography (TCD). Results: Under the hypervolemic hemodilution supported with dopamine/dobutamine, a dosage-dependent increase of 12% in blood pressure and a 53% increase in cardiac output was observed. In the affected hemisphere, flow velocity was one fourth lower (significance p < 0.05) than in the unaffected hemisphere. With therapy, the systolic flow velocity was increased in the unaffected hemisphere by 27%, on the side of the lesion only by 11%. Mean flow velocity remained nearly constant. The pulsatility index (PI) increased simultaneously by 46% in the affected and 47% in the unaffected hemisphere. Conclusion: Similar effects on TCD-flow velocity and PI under comparable slight increases in blood pressure are not known. The increase in cerebrovascular resistance can be ascribed to a counter-regulation of the cerebral autoregulation, triggered by an increase of cardiac output.