Transcranial Doppler ultrasound: Physical principles and principal applications in Neurocritical care unit

Abstract

Transcranial Doppler (TCD) ultrasonography is a noninvasive ultrasound study, which has been extensively applied on both outpatient and inpatient settings. It involves the use of a low-frequency (≤2 MHz) transducer, placed on the scalp, to insonate the basal cerebral arteries through relatively thin bone windows and to measure the cerebral blood flow velocity and its alteration in many different conditions. In neurointensive care setting, TCD is useful for both adults and children for day-to-day bedside assessment of critical conditions including vasospasm in subarachnoid hemorrhage, traumatic brain injury, acute ischemic stroke, and brain stem death. It also allows to investigate the cerebrovascular autoregulation in setting of carotid disease and syncope. In this review, we will describe physical principles underlying TCD, flow indices most frequently used in clinical practice and critical care applications in Neurocritical Unit care.

Cerebral Hemodynamic Changes to Transcranial Doppler in Asymptomatic Patients with Fabry’s Disease

“…Changes in RI reflect a disease pattern similar to that observed in case of abnormal PI. Namely, RI values > 0.8 indicate increased downstream resistance, while hyperemia, arteriovenous malformation, vasospasm, and rewarming following hypothermia can lead to decreased RI [58,59]. Vasodilation stimulation via breath-holding and CO 2 -induced hypercapnia can detect impaired cerebral vasomotor reserve and predict the risk of stroke [54].…”

Point of Care Cranial Ultrasound in a Hemicraniectomy Patient

“…Point-of-care ultrasound allows for the assessment of midline shift, brainstem, and ventricles, and Doppler allows visualization of cerebral perfusion patterns. 1 , 2 Patients with a hemicraniectomy have better temporal windows available since a portion of their skull has been removed. In such patients, ultrasound can provide a non-invasive method to serially assess midline shift, intracranial hematomas, and focal ischemia at the bedside.…”

Transcranial colour‐coded duplex of the intracranial large arteries

“…TCCD can be useful in detecting and monitoring the changes in flow velocities associated with vasospasm . Detection of vasospasm helps with the timing and need for neurosurgical or endovascular therapies and can subsequently assist in monitoring the efficacy of interventions …”