Correlation Between Transcranial Doppler Ultrasonography and Regional Cerebral Blood Flow in Experimental Intracranial Hypertension

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Abstract
Background and Purpose Transcranial Doppler ultrasonography (TCD) provides useful information on cerebral circulation even under raised intracranial pressure. This study was designed to evaluate the correlation between cerebral blood flow (CBF) and TCD parameters under conditions of boundary intracranial hypertension that can cause brain death. Methods Intracranial pressure was raised by inflation of a supratentorial epidural balloon in cats. Blood flow velocity of the middle cerebral artery was measured transorbitally with microvascular Doppler sonography, and intracranial pressure and CBF were evaluated. Results In this study, four characteristic flow patterns were observed, appearing in the following order with progressive increases in intracranial pressure: sharp wave, systolic flow, systolic spike, and no flow. These flow patterns showed a significant correlation with flow velocity, CBF, the pulsatility index, and cerebral perfusion pressure. The systolic-spike and no-flow patterns and pulsatility index over 4.0 indicated decreased CBF, under 10% of control values. Conclusions The critical level of brain circulation can be detected by Doppler sonography, indicating that TCD is available as a tool for the assessment of cerebral circulatory arrest in brain death.