Acute Neurologic Injury in ICU: Vasomotor Reactivity Testing by Transcranial Doppler (TCD/TCCS)

Cerebral vasoreactivity or vasomotor reactivity is an index of cerebral blood flow or velocity in response after administration of a vasomodulatory stimulus, whether it is a drug (e.g. acetazolamide intravenous), gases (e.g. carbogen), or a manoeuvre that causes changes in PaCO2 (e.g. apnoea or hyperventilation). Breath-hold test, carbogen inhalation and acetazolamide are the most commonly used stimulus. The use of a transcranial Doppler probe holder is essential to minimize the errors, and expired carbon dioxide is also important in vasoreactivity quantification. Worse vasoreactivity has been linked to prognosis in critical care patients. These patients are at higher risk of cerebral ischemic lesions.