Transcranial Doppler examination on effect of hemodynamics on cerebral autoregulation in acute cerebral infarct

Abstract

We treated 24 patients suffering from an acute ischemic stroke of the middle cerebral artery, with a hypervolemic hemodilution combined with dopamine/dobutamine. 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). 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 11%. Mean flow velocity remained nearly constant. The pulsatility index (PI) increased simultaneously by 46% in the affected and 47% in the unaffected hemisphere. 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.