ASNM and ASN joint guidelines for transcranial Doppler ultrasonic monitoring: An update

Abstract

Today, it seems prudent to reconsider how ultrasound technology can be used for providing intraoperative neurophysiologic monitoring that will result in better patient outcomes and decreased length and cost of hospitalization. An extensive and rapidly growing literature suggests that the essential hemodynamic information provided by transcranial Doppler (TCD) ultrasonography neuromonitoring (TCDNM) would provide effective monitoring modality for improving outcomes after different types of vascular, neurosurgical, orthopedic, cardiovascular, and cardiothoracic surgeries and some endovascular interventional or diagnostic procedures, like cardiac catheterization or cerebral angiography.Understanding, avoiding, and preventing peri-or postoperative complications, including neurological deficits following abovementioned surgeries, endovascular intervention, or diagnostic procedures, represents an area of great public and economic benefit for society, especially considering the aging population. The American Society of Neurophysiologic Monitoring and American Society of Neuroimaging Guidelines Committees formed a joint task force and developed updated guidelines to assist in the use of TCDNM in the surgical and intensive care settings. Specifically, these guidelines define (1) the objectives of TCD monitoring; (2) the responsibilities and behaviors of the neurosonographer during monitoring; (3) instrumentation and acquisition parameters; (4) safety considerations; (5) contemporary rationale for TCDNM; (6) TCDNM perspectives; and (7) major recommendations.

Carotid Endarterectomy Surgeries: A Multimodality Intraoperative Neurophysiological Monitoring Approach

“…Patients with poor collateral circulation have a lesser degree of circulation in cases of blockage. The presence of more than one HITS per minute may be predictive of an impending stroke, and the surgeon should be alerted [13]. Previous literature has shown a significant correlation between the presence of more than 10 emboli and peri-and postoperative cerebral complications and warrants notifying the surgeon [13].…”

“…Transcranial Doppler (TCD) ultrasound provides a rapid, noninvasive, real-time measure of cerebrovascular function. TCD can be used to measure blood flow velocity in the basal arteries of the brain to assess relative changes in flow, diagnose focal vascular stenosis, or detect embolic signals within these arteries [ 13 ]. TCD can also be used to assess the physiologic health of vascular territory by measuring blood flow responses to changes in blood pressure (cerebral autoregulation), changes in end-tidal CO 2 (cerebral vasoreactivity), or cognitive and motor activation (neurovascular coupling or functional hyperemia) [ 13 ].…”

“…TCD utilizes ultrasonic 2 MHz probes which can be fixed to the temporal window for middle cerebral artery monitoring to examine the circle of Willis’ perfusion (Figure 5 ) [ 13 ]. Optimal visualization of TCD signals requires a high-pass filter (HPF) for minimization of vessel motion artifact, and in some cases, HPF may need to be disabled in cases of low cerebral blood flow (CBF) velocity (Figure 6 ) [ 13 ]. High-intensity transient signals (HITS) have an amplitude above 3 dB, duration less than 300 ms, with a unidirectional acoustic sound such as a snap (Figure 7 ).…”

“…Cross clamping may show a decrease in CBF with a more than 85% decrease denoting severe ischemia, and a 60-85% decrease denoting moderate ischemia. TCD monitoring should be used continuously throughout the procedure for measuring CBF velocity and detecting possible embolic signals [ 13 , 14 ].…”

“…The presence of more than one HITS per minute may be predictive of an impending stroke, and the surgeon should be alerted [ 13 ]. Previous literature has shown a significant correlation between the presence of more than 10 emboli and peri- and postoperative cerebral complications and warrants notifying the surgeon [ 13 ]. The limitations of using TCD are the need for an experienced TCD technologist and the difficulty in using it on patients without a good window.…”