Use of Transcranial Doppler (TCD) Ultrasound in the Neurocritical Care Unit

Transcranial Doppler (TCD) is a bedside procedure that measures linear cerebral blood flow velocity (CBFV) through the intracranial circulation and pulsatility index (PI). Several different disease processes can lead to intracerebral vasospasm, for example after subarachnoid hemorrhage, and traumatic brain injury. Intracerebral vasospasm will be represented by abnormally high CBFV. The PI’s changes can be used for evaluation of high intracranial pressure (ICP). The PI is the reflection of downstream resistance and will be affected by abnormally high ICP. TCD can be used for detection of cerebral vessel occlusion and estimation of cerebrovascular reactivity. Contrast TCD is used for the diagnosis of right to left cardiac shunts, for patients with cryptogenic stroke. TCD is the unique standard for the detection of microembolic signals in real-time. TCD has high accuracy to confirm total cerebral circulatory arrest and has been used as an ancillary test to support clinical diagnosis of brain death.