Persistence of isolated flow in the internal carotid artery in brain death

The criteria for the confirmation of brain death (BD) using transcranial Doppler ultrasonography (TCD) state that flow should not be observed in the internal carotid artery (ICA). In 94 brain-dead patients examined by TCD, 19 (20%) had flow in the ICA despite cerebral circulatory arrest. There was no difference in the clinical characteristics of patients with or without isolated flow in the ICA. Shunting of blood from the ICA into the external carotid system or the arrest of blood flow at a higher level than the carotid siphon may explain our findings. Our results show that the current TCD criteria can result in a high rate of false negatives. We suggest that the TCD criteria for the diagnosis of brain death should be reviewed.