Variability Of Transcranial Doppler Criteria In The Determination Of Cerebral Circulatory Arrest

Introduction: Transcranial Doppler (TCD) is a commonly used testing modality in the diagnosis of cerebral circulatory arrest (CCA). There is currently no consensus in the United States for which vessels must be insonated to establish a CCA diagnosis. We evaluated TCD-CCA studies using four categories of vessel selection to determine which set of criteria would be most restrictive. Methods: We reviewed all TCD studies from our center that were performed for the evaluation of CCA. For each study, two readers determined whether the bilateral middle cerebral arteries (MCA) and the basilar artery demonstrated a pattern typical of CCA. In cases where one or more of these three primary vessels could not be located, specific proximal vessels were evaluated and used as a surrogate. Surrogate vessels for the MCAs included the ipsilateral carotid siphon and the terminal internal carotid artery. Surrogate vessels for the basilar artery required the evaluation of both intracranial vertebral arteries. A diagnosis of CCA was given according to four different criteria: absent diastolic flow in [1] bilateral MCAs and the basilar artery, [2] bilateral MCAs only, [3] the three primary vessels or a surrogate vessel when a primary vessel could not be located, and [4] bilateral MCAs or a surrogate vessel when either MCA could not be located. Results: Fifty-five TCD studies were included in this analysis. Of these, 17 studies were not able to insonate one of the three primary vessels. Seven of these incomplete studies included surrogate vessels for the absent primary vessel. When all three primary vessels were insonated, 17 studies were consistent with CCA. Twenty-four studies met CCA criteria when only the MCAs were evaluated, 19 studies met criteria when the primary vessels or a surrogate vessel were evaluated, and 26 studies met criteria when only the MCAs or their surrogate vessels were evaluated. Conclusion: The results of this analysis suggest that when different criteria for CCA are applied, the rates of CCA diagnosis change considerably. Since CCA is often a critical part of establishing death by neurologic criteria, it is important that national standards for a TCD protocol are established.