Transcranial Doppler Monitoring in Carotid Endarterectomy: A Systematic Review and Meta-analysis

Robotic Assisted Transcranial Doppler Monitoring in Acute Neurovascular Care: A Feasibility and Safety Study

BACKGROUND

Transcranial color Doppler (TCD) is currently the only noninvasive bedside tool capable of providing real-time information on cerebral hemodynamics. However, being operator dependent, TCD monitoring is not feasible in many institutions. Robotic assisted TCD (ra-TCD) was recently developed to overcome these constraints. The aim of this study was to evaluate the safety and feasibility of cerebral monitoring with a novel ra-TCD in acute neurovascular care.

METHODS

This is a two-center prospective study conducted between August 2021 and February 2022 at Padua University Hospital (Padua, Italy) and Kepler University Hospital (Linz, Austria). Adult patients with conditions impacting cerebral hemodynamics or patients undergoing invasive procedures affecting cerebral hemodynamics were recruited for prolonged monitoring (> 30 min) of the middle cerebral artery with a novel ra-TCD (NovaGuide Intelligent Ultrasound, NeuraSignal, Los Angeles, CA). Manual TCD was also performed for comparison by an experienced operator. Feasibility and safety rates were recorded.

RESULTS

A total of 92 patients (age: mean 68.5 years, range 36-91; sex: male 57 [62%]) were enrolled in the two centers: 54 in Padua, 38 in Linz. The examination was feasible in the majority of patients (85.9%); the head cradle design and its radiopacity hindered its use during carotid endarterectomy and mechanical thrombectomy. Regarding safety, only one patient (1.1%) reported a minor local edema due to prolonged probe pressure. Velocity values were similar between ra-TCD and manual TCD.

CONCLUSIONS

This novel ra-TCD showed an excellent safety and feasibility and proved to be as reliable as manual TCD in detecting blood flow velocities. These findings support its wider use for cerebral hemodynamics monitoring in acute neurovascular care. However, further technical improvements are needed to expand the range of applicable settings.

Predictive Factors Driving Positive Awake Test in Carotid Endarterectomy Using Machine Learning

BACKGROUND

Positive neurologic awake testing during the carotid cross-clamping may be present in around 8% of patients undergoing carotid endarterectomy (CEA). The present work aimed to assess the accuracy of an artificial intelligence (AI)-powered risk calculator in predicting intraoperative neurologic deficits (INDs).

METHODS

Data was collected from carotid interventions performed between January 2012 and January 2023 under regional anesthesia. Patients with IND were selected along with consecutive controls without IND in a case-control study design. A predictive model for IND was developed using machine learning, specifically Extreme Gradient Boosting (XGBoost) model, and its performance was assessed and compared to an existing predictive model. Shapley Additive exPlanations (SHAP) analysis was employed for the model interpretation.

RESULTS

Among 216 patients, 108 experienced IND during CEA. The AI-based predictive model achieved a robust area under the curve of 0.82, with an accuracy of 0.75, precision of 0.88, sensitivity of 0.59, and F1Score of 0.71. High body mass index (BMI) increased contralateral carotid stenosis, and a history of limb paresis or plegia were significant IND risk factors. Elevated preoperative platelet and hemoglobin levels were associated with reduced IND risk.

CONCLUSIONS

This AI model provides precise IND prediction in CEA, enabling tailored interventions for high-risk patients and ultimately improving surgical outcomes. BMI, contralateral stenosis, and selected blood parameters emerged as pivotal predictors, bringing significant advancements to decision-making in CEA procedures. Further validation in larger cohorts is essential for broader clinical implementation.

Brazilian Angiology and Vascular Surgery Society Guidelines for the treatment of extracranial cerebrovascular disease

Extracranial cerebrovascular disease has been the subject of intense research throughout the world, and is of paramount importance for vascular surgeons. This guideline, written by the Brazilian Society of Angiology and Vascular Surgery (SBACV), supersedes the 2015 guideline. Non-atherosclerotic carotid artery diseases were not included in this document. The purpose of this guideline is to bring together the most robust evidence in this area in order to help specialists in the treatment decision-making process. The AGREE II methodology and the European Society of Cardiology system were used for recommendations and levels of evidence. The recommendations were graded from I to III, and levels of evidence were classified as A, B, or C. This guideline is divided into 11 chapters dealing with the various aspects of extracranial cerebrovascular disease: diagnosis, treatments and complications, based on up-to-date knowledge and the recommendations proposed by SBACV.

Risk of perioperative stroke and cerebral autoregulation monitoring: a systematic review

BACKGROUND

Perioperative stroke, delirium, and cognitive impairment could be related to management and to variations in blood pressure control, cerebral hypoperfusion and raised blood volume. Cerebral autoregulation (CAR) is a mechanism to maintain cerebral perfusion through the control of the vascular tone and hemodynamic reactions in the circulation.

OBJECTIVE

The present systematic review addresses the relationship between impaired CAR and perioperative stroke by evaluating the rate of neurological complications after surgery in studies in which perioperative CAR was tested or monitored.

METHODS

We included randomized clinical trials and prospective observational studies. All studies had adjusted the relative risk, hazard ratio or 95% confidence interval (95%CI) values. These estimation effects were tested using random-effects models. Heterogeneity among the selected studies was assessed using the Higgins and Thompson I² statistics.

RESULTS

The Web of Science, PubMed and EMBASE electronic databases were searched to retrieve articles. A total of 4,476 studies published between 1983 and 2019 were analyzed, but only 5 qualified for the data extraction and were included in the final analysis. The combined study cohort comprised 941 patients who underwent CAR monitoring during surgical procedures. All studies provided information about perioperative stroke, which equated to 16% (158 of 941) of the overall patient population.

CONCLUSION

The present meta-analysis showed evidence of the impact of CAR impairment in the risk of perioperative stroke. On the pooled analysis, blood fluctuations or other brain insults large enough to compromise CAR were associated with the outcome of stroke (odds ratio [OR]: 2.26; 95%CI: 1.54-2.98; p < 0.0001).

Application of transcranial Doppler in cerebrovascular diseases

Transcranial Doppler (TCD) is a rapid and non-invasive diagnostic technique that can provide real-time measurements of the relative changes in cerebral blood velocity (CBV). Therefore, TCD is a useful tool in the diagnosis and treatment of clinical cerebrovascular diseases (CVDs). In this review, the basic principles of TCD and its application in CVD were outlined. Specifically, TCD could be applied to evaluate occlusive CVD, assess collateral circulation in patients with ischemic stroke, and monitor cerebral vascular occlusion before and after thrombolysis as well as cerebral vasospasm (VSP) and microembolization signals after aneurysmal subarachnoid hemorrhage (SAH). Moreover, TCD could predict short-term stroke and transient cerebral ischemia in patients with anterior circulation occlusion treated with endovascular therapy and in patients with anterior circulation vascular occlusion. Additionally, TCD not only could monitor blood velocity signals during carotid endarterectomy (CEA) or carotid artery stenting (CAS) but also allowed earlier intervention through early recognition of sickle cell disease (SCD). Presently, TCD is a useful prognostic tool to guide the treatment of CVD. On the one hand, TCD is more commonly applied in clinical research, and on the other hand, TCD has an increasing role in the management of patients. Collectively, we review the principles and clinical application of TCD and propose some new research applications for TCD.

A systematic review & meta-analysis on perioperative cerebral and hemodynamic monitoring methods during carotid endarterectomy

OBJECTIVE

To compare outcomes between different strategies of perioperative cerebral and hemodynamic monitoring during carotid endarterectomy.

DATA SOURCES

MEDLINE, EMBASE, CINAHL, and Cochrane CENTRAL databases were searched.

METHODS

This review was performed according to the PRISMA guidelines and prospectively registered in the international prospective register of systematic reviews (CRD42021241891). The GRADE approach was used to describe the methodological quality of the studies and certainty of the evidence. The primary outcome was 30-day stroke rate. Secondary outcomes measures are 30-day ipsilateral stroke, 30-day mortality, shunt rate and complication rates.

RESULTS

The search identified 3 460 articles. Seventeen RCTs, three prospective observational studies and seven registries were included, reporting on 236 983 patients. The overall pooled 30-day stroke rate is 1.8% (95% CI 1.4 - 2.2%), ranging from 0 - 12.6%. In RCT's the pooled 30-day stroke rate is 2.7% (95% CI 1.6 - 3.7%) compared to 1.3% (95%CI 0.8 - 1.8%) in the registries. The overall stroke risk decreased from 3.7% before the year 2000 to 1.6% after 2000. No significant differences could be identified between different monitoring and shunting strategies, although a trend to higher stroke rates in routine no shunting arms of RCTs was observed. Overall 30-day mortality, myocardial infarction and nerve injury rates are 0.6% (95%CI 0.4 - 0.8), 0.8% (95%CI 0.6-1.0) and 1.3% (95%CI 0.4-2.2), respectively.

CONCLUSIONS

No significant differences between the compared shunting and monitoring strategies are found. However, routine no shunting is not recommended. The available data is too limited to prefer one method of neuromonitoring over another method when selective shunting is applied.

Perioperative stroke during carotid endarterectomy: benefits of multimodal neuromonitoring - a case report

Background

Carotid endarterectomy is routinely performed after ischemic stroke due to carotid stenosis. Perioperative, cerebral blood flow and oxygenation can be monitored in different ways, but there is no clear evidence of a gold standard and a uniform guideline is lacking. Electroencephalography and near-infrared spectroscopy are among the most frequently used methods of neuromonitoring. Clinicians should be aware of their pitfalls and the added value of transcranial doppler.

Case presentation

We present the case of an 85-year old male with perioperative haemodynamic stroke during carotid endarterectomy. Ischemic stroke was caused by suddenly increased carotid stenosis resulting in major neurologic deficit. This was registered only by transcranial doppler, while surface electroencephalography and near-infrared spectroscopy failed to detect any significant change in cerebral perfusion, despite a large perfusion defect on computed tomography. Circulation was restored with endovascular treatment and neurologic deficit quickly resolved.

Conclusion

We strongly advocate the practice of multimodal neuromonitoring including transcranial doppler whenever possible to minimize the risk of persistent neurologic deficit due to perioperative stroke during carotid endarterectomy.

Carotid Endarterectomy Surgeries: A Multimodality Intraoperative Neurophysiological Monitoring Approach

Patients with untreated carotid artery stenosis remain at high risk for stroke. Carotid endarterectomy (CEA) is a surgical procedure for the treatment of symptomatic and severe asymptomatic carotid stenosis. A small percentage of patients who do not have good collateral circulation are at high risk of cerebral ischemia during the cross-clamping of the carotid artery. Aspects of CEA, such as cross-clamping and routine shunting, can also carry the risk of perioperative stroke through dislodgement of emboli causing thrombosis, therefore, selective shunting is highly recommended during the CEA procedure. A multimodality approach of intraoperative neurophysiological monitoring (IONM) techniques such as somatosensory evoked potential (SSEP) and electroencephalography (EEG) can be used to monitor cerebral perfusion throughout the duration of the surgery and to predict the need for a selective shunt after cross-clamping. Additional use of transcranial Doppler (TCD) in the multimodality approach can aid in visualizing the cerebral blood flow and detecting any microemboli that may also cause a stroke. A multimodality IONM approach has been reported as more sensitive and specific for predicting and minimizing any postoperative neurological deficits.

Anesthetic management of carotid endarterectomy: an update from Italian guidelines

BACKGROUND AND AIMS

In order to systematically review the latest evidence on anesthesia, intraoperative neurologic monitoring, postoperative heparin reversal, and postoperative blood pressure management for carotid endarterectomy. The present review is based on a single chapter of the Italian Health Institute Guidelines for diagnosis and treatment of extracranial carotid stenosis and stroke prevention.

METHODS AND RESULTS

A systematic article review focused on the previously cited topics published between January 2016 and October 2020 has been performed; we looked for both primary and secondary studies in the extensive archive of Medline/PubMed and Cochrane library databases. We selected 14 systematic reviews and meta-analyses, 13 randomized controlled trials, 8 observational studies, and 1 narrative review. Based on this analysis, syntheses of the available evidence were shared and recommendations were indicated complying with the GRADE-SIGN version methodology.

CONCLUSIONS

From this up-to-date analysis, it has emerged that any type of anesthesia and neurological monitoring method is related to a better outcome after carotid endarterectomy. In addition, insufficient evidence was found to justify reversal or no-reversal of heparin at the end of surgery. Furthermore, despite a low evidence level, a suggestion for blood pressure monitoring in the postoperative period was formulated.

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

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.

Overview and Diagnostic Accuracy of Near Infrared Spectroscopy in Carotid Endarterectomy: A Systematic Review and Meta-analysis

OBJECTIVE

Carotid endarterectomy is recommended for the prevention of ischaemic stroke due to carotid stenosis. However, the risk of stroke after carotid endarterectomy has been estimated at 2% - 5%. Monitoring intra-operative cerebral oxygenation with near infrared spectroscopy (NIRS) has been assessed as a strategy to reduce intra- and post-operative complications. The aim was to summarise the diagnostic accuracy of NIRS to detect intra-operative ischaemic events, the values associated with ischaemic events, and the relative contribution of external carotid contamination to the NIRS signal in adults undergoing carotid endarterectomy.

DATA SOURCES

EMBASE, MEDLINE, Cochrane Centre Register of Controlled Trials, and reference lists through May 2019 were searched.

REVIEW METHODS

Non-randomised and randomised studies assessing NIRS as an intra-operative monitoring tool in carotid endarterectomy were included. Studies using NIRS as the reference were excluded. Risk of bias was assessed using the Newcastle Ottawa Scale, RoB-2, and QUADAS-2.

RESULTS

Seventy-six studies were included (n = 8 480), under local (n = 1 864) or general (n = 6 582) anaesthesia. Seven studies were eligible for meta-analysis (n = 524). As a tool for identifying intra-operative ischaemia, specificity increased with more stringent NIRS thresholds, while there was unpredictable variation in sensitivity across studies. A Δ20% threshold under local anaesthesia resulted in pooled estimates for sensitivity and specificity of 70.5% (95% confidence interval, CI, 54.1 - 82.9) and 92.4% (95% CI 85.5 - 96.1) compared with awake neurological monitoring. These studies had low or unclear risk of bias. NIRS signal consistently dropped across clamping and recovered to pre-clamp values upon de-clamp in most studies, and larger decreases were observed in patients with ischaemic events. The contribution of extracranial signal to change in signal across clamp varied from 3% to 50%.

CONCLUSION

NIRS has low sensitivity and high specificity to identify intra-operative ischaemia compared with awake monitoring. Extracranial signal contribution was highly variable. Ultimately, data from high quality studies are desperately needed to determine the utility of NIRS.

Intraoperative Cerebral Monitoring During Carotid Surgery: A Narrative Review

BACKGROUND

Intra-operative neurological monitoring (IONM) during carotid endarterectomy (CEA) aims to reduce neurological morbidity of surgery.

OBJECTIVE

This narrative review analyses the role and results of different methods of IONM.

METHODS

review articles on PUBMED and Cochrane Library, by searching key words related to IONM and CEA, from 2000 up to date.

RESULTS

regional anesthesia in some centers represents the "gold standard". The most often used alternative techniques are: stump pressure, electroencephalogram, somatosensory evoked potentials, transcranical doppler ultrasound, near infrared spectroscopy and routine shunting. Every technique shows limitations. Regional anesthesia can make difficult prompt intubation when needed. Stump pressure shows a wide operative range. Electroencephalogram is unable to detect ischemia in sub-cortical regions of the brain. Somatosensory evoked potentials certainly demonstrate the presence of cerebral ischemia, but are no more specific or sensitive than the electroencephalogram. Transcranical doppler monitoring is undoubtedly operator-dependent and suffers from the limitations that the probe has to be placed relatively near to the surgical site and may impede the operator, especially if it needs constant adjustments; moreover, an acoustic window may not be found in 10% -20% of the subjects. Near infrared spectroscopy appears to have a high negative predictive value for cerebral ischemia, but has a poor positive predictive value and low specificity, because predominantly estimates venous oxygenation as this makes up about 80% of cerebral blood volume. The data on the use of Routine Shunting (RS) from RCTs are limited.

CONCLUSIONS

currently, with no clear consensus on monitoring technique, choice should be guided by local expertise and complication rates. With reflection, best practice may dictate that a standard technique is selected as suggested above and this remains the default position for individual practice. Nevertheless, current techniques for monitoring cerebral perfusion during CEA are associated with false negative and false positive resulting in inappropriate shunt insertion.

Cerebral Perfusion and Brain Oxygen Saturation Monitoring with: Jugular Venous Oxygen Saturation, Cerebral Oximetry, and Transcranial Doppler Ultrasonography

Accumulating evidence indicates that cerebral desaturation in the perioperative period occurs more frequently than recognized. Combining monitoring modalities that reflect different aspects of cerebral perfusion status, such as near-infrared spectroscopy, jugular bulb saturation, and transcranial Doppler ultrasonography, may provide an extended window for prevention, early detection, and prompt intervention in ongoing hypoxic/ischemic neuronal injury and, thereby, improve neurologic outcome. Such an approach would minimize the impact of limitations of each monitoring modality, while individual components complement each other, enhancing the accuracy of acquired information. Current literature has failed to demonstrate any clear-cut clinical benefit of these modalities on outcome prognosis.

The Diagnostic Accuracy of Intra-Operative Near Infrared Spectroscopy in Carotid Artery Endarterectomy Under Regional Anaesthesia: Systematic Review and Meta-Analysis

OBJECTIVE

Intra-operative near infrared spectroscopy (NIRS) is a non-invasive tool used to monitor regional cerebral oxygen saturation during carotid endarterectomy (CEA), for which accuracy remains unclear. Therefore, this systematic review and meta-analysis aimed to determine the diagnostic accuracy of NIRS in patients undergoing CEA under regional anaesthesia (RA).

DATA SOURCES

MEDLINE, Scopus, and Web of Science were searched for studies that compared NIRS with the "awake test" in patients undergoing CEA under RA.

REVIEW METHODS

Bivariable random effects meta-analysis was performed to determine the diagnostic accuracy of NIRS to detect cerebral ischaemia. Meta-regression was performed to explore causes of heterogeneity. Meta-analysis of proportions was also performed to determine the accuracy of NIRS in predicting 30 day stroke. Study quality was evaluated using the QUADAS-2 criteria.

RESULTS

Eleven primary studies were included, assessing 1 237 participants. The meta-analysis obtained a partial area under the summary receiver operating characteristic curve for diagnosing brain ischaemia of 0.646, with a summary sensitivity of 72.0% (95% confidence interval [CI] 58.1 - 82.7; I² = 48.6%) and a specificity of 84.1% (95% CI 78.5-88.4; I² = 48.6%). In meta-regression analysis, the frequency of hypertension (p = .011) and patients with symptomatic carotid stenosis (p = .031) were significant effect modifiers. Higher frequency of arterial hypertension (z score = -2.15; p = .032) and diabetes (z score = -2.12; p = .034) were associated with lower summary sensitivity, while a higher frequency of symptomatic carotid stenosis (z score = 2.11; p = .035) was associated with higher summary sensitivity. Point estimate sensitivity and specificity for predicting 30 day stroke occurrence were 41% (95% CI 19.5 - 66.6; I² = 0%) and 81.4% (95% CI 74.4 - 86.9, I² = 65.6%), respectively.

CONCLUSION

The results of this study suggest that NIRS as a cerebral monitoring technique does not have sufficiently high sensitivity or specificity to be used alone in the neurological monitoring of patients undergoing CEA under RA.

Cerebral Emboli Monitoring Using Transcranial Doppler Ultrasonography in Adults and Children: A Review of the Current Technology and Clinical Applications in the Perioperative and Intensive Care Setting

Transcranial Doppler (TCD) ultrasonography is the only noninvasive bedside technology for the detection and monitoring of cerebral embolism. TCD may identify patients at risk of acute and chronic neurologic injury from gaseous or solid emboli. Importantly, a window of opportunity for intervention-to eliminate the source of the emboli and thereby prevent subsequent development of a clinical or subclinical stroke-may be identified using TCD. In this review, we discuss the application of TCD sonography in the perioperative and intensive care setting in adults and children known to be at increased risk of cerebral embolism. The major challenge for evaluation of emboli, especially in children, is the need to establish the ground truth and define true emboli identified by TCD. This requires the development and validation of a predictive TCD emboli monitoring technique so that appropriately designed clinical studies intended to identify specific modifiable factors and develop potential strategies to reduce pathologic cerebral embolic burden can be performed.

Cerebral ischemia detection using artificial intelligence (CIDAI)-A study protocol

BACKGROUND

The onset of cerebral ischemia is difficult to predict in patients with altered consciousness using the methods available. We hypothesize that changes in Heart Rate Variability (HRV), Near-Infrared Spectroscopy (NIRS), and Electroencephalography (EEG) correlated with clinical data and processed by artificial intelligence (AI) can indicate the development of imminent cerebral ischemia and reperfusion, respectively. This study aimed to develop a method that enables detection of imminent cerebral ischemia in unconscious patients, noninvasively and with the support of AI.

METHODS

This prospective observational study will include patients undergoing elective surgery for carotid endarterectomy and patients undergoing acute endovascular embolectomy for cerebral arterial embolism. HRV, NIRS, and EEG measurements and clinical information on patient status will be collected and processed using machine learning. The study will take place at Sahlgrenska University Hospital, Gothenburg, Sweden. Inclusion will start in September 2020, and patients will be included until a robust model can be constructed. By analyzing changes in HRV, EEG, and NIRS measurements in conjunction with cerebral ischemia or cerebral reperfusion, it should be possible to train artificial neural networks to detect patterns of impending cerebral ischemia. The analysis will be performed using machine learning with long short-term memory artificial neural networks combined with convolutional layers to identify patterns consistent with cerebral ischemia and reperfusion.

DISCUSSION

Early signs of cerebral ischemia could be detected more rapidly by identifying patterns in integrated, continuously collected physiological data processed by AI. Clinicians could then be alerted, and appropriate actions could be taken to improve patient outcomes.

Surgical Technique for Carotid Endarterectomy: Current Methods and Problems

Over the last 60 years, many reports have investigated carotid endarterectomy (CEA) and techniques have thus changed and improved. In this paper, we review the recent literature regarding operational maneuvers for CEA and discuss future problems for CEA. Longitudinal skin incision is common, but the transverse incision has been reported to offer minimal invasiveness and better cosmetic effects for CEA. Most surgeons currently use microscopy for dissection of the artery and plaque. Although no monitoring technique during CEA has been proven superior, multiple monitors offer better sensitivity for predicting postoperative neurological deficit. To date, data are lacking regarding whether routine shunt or selective shunt is better. Individual surgeons thus need to select the method with which they are more comfortable. Many surgical techniques have been reported to obtain distal control of the internal carotid artery in patients with high cervical carotid bifurcation or high plaque, and minimally invasive techniques should be considered. Multiple studies have shown that patch angioplasty reduces the risks of stroke and restenosis compared with primary closure, but few surgeons in Japan have been performing patch angioplasty. Most surgeons thus experience only a small volume of CEAs in Japan, so training programs and development of in vivo training models are important.

Cerebral monitoring during transcarotid artery revascularization with flow reversal via transcranial doppler ultrasound examination

OBJECTIVE

Transcarotid artery revascularization (TCAR) is a hybrid technique for carotid artery revascularization that relies on proximal carotid occlusion with flow reversal for distal embolic protection. The hemodynamic response of the intracranial circulation to flow reversal is unknown. In addition, the rate and pattern of cerebral embolization during flow reversal has yet to be investigated. The aim of this study was to characterize cerebral hemodynamic and embolization patterns during TCAR.

METHODS

A single-institution retrospective study of patients with carotid artery stenosis undergoing TCAR with intraoperative transcranial Doppler (TCD) monitoring of the middle cerebral artery (MCA) was performed. Primary outcomes included changes in MCA velocity and MCA embolic signals observed throughout TCAR.

RESULTS

Eleven patients underwent TCAR with TCD monitoring of the ipsilateral MCA. The average MCA velocity at baseline was 50.6 ± 16.4 cm/s. MCA flow decreased significantly upon initiation of flow reversal (50.5 ± 16.4 cm/s vs 19.1 ± 18.4 cm/s; P = .02). The reinitiation of antegrade flow resulted in a significant increase in the number of embolic events compared with baseline (P = .003), and embolic events were observed in two patients during flow reversal.

CONCLUSIONS

TCD monitoring of patients undergoing TCAR revealed that the initiation of flow reversal results in a decrement in ipsilateral MCA velocity. Furthermore, embolic events can occur during flow reversal and are significantly associated with the reinitiation of antegrade flow in the internal carotid artery. However, both of these hemodynamic events were well-tolerated in our cohort. These findings suggest that TCAR remains a safe neuroprotective strategy for carotid revascularization.

Cesarean section under general anesthesia for antepartum reversible cerebral vasoconstriction syndrome: A case report

Reversible cerebral vasoconstriction syndrome (RCVS) is characterized by acute and usually severe headache related to multifocal vasoconstriction of cerebral arteries, reversible within 3 months. About 10% of RCVS are pregnancy-related, but only three cases of antepartum RCVS have been described. We report the case of a 26-year-old pregnant woman who presented at 36 weeks gestation with antepartum RCVS. Delivery was managed by cesarean section under general anesthesia. Though she developed focal neurologic deficits on the first postoperative day, these resolved at hospital discharge. This case highlights pre- and post-partum multidisciplinary management including cesarean section under general anesthesia.

Reproducibility of Transcranial Doppler ultrasound in the middle cerebral artery

BACKGROUND

Transcranial Doppler ultrasound remains the only imaging modality that is capable of real-time measurements of blood flow velocity and microembolic signals in the cerebral circulation. We here assessed the repeatability and reproducibility of transcranial Doppler ultrasound in healthy volunteers and patients with symptomatic carotid artery stenosis.

METHODS

Between March and August 2017, we recruited 20 healthy volunteers and 20 patients with symptomatic carotid artery stenosis. In a quiet temperature-controlled room, two 1-h transcranial Doppler measurements of blood flow velocities and microembolic signals were performed sequentially on the same day (within-day repeatability) and a third 7-14 days later (between-day reproducibility). Levels of agreement were assessed by interclass correlation co-efficient.

RESULTS

In healthy volunteers (31±9 years, 11 male), within-day repeatability of Doppler measurements were 0.880 (95% CI 0.726-0.950) for peak velocity, 0.867 (95% CI 0.700-0.945) for mean velocity, and 0.887 (95% CI 0.741-0.953) for end-diastolic velocity. Between-day reproducibility was similar but lower: 0.777 (95% CI 0.526-0.905), 0.795 (95% CI 0.558-0.913), and 0.674 (95% CI 0.349-0.856) respectively. In patients (72±11 years, 11 male), within-day repeatability of Doppler measurements were higher: 0.926 (95% CI 0.826-0.970) for peak velocity, 0.922 (95% CI 0.817-0.968) for mean velocity, and 0.868 (95% CI 0.701-0.945) for end-diastolic velocity. Similarly, between-day reproducibility revealed lower values: 0.800 (95% CI 0.567-0.915), 0.786 (95% CI 0.542-0.909), and 0.778 (95% CI 0.527-0.905) respectively. In both cohorts, the intra-observer Bland Altman analysis demonstrated acceptable mean measurement differences and limits of agreement between series of middle cerebral artery velocity measurements with very few outliers. In patients, the carotid stenoses were 30-40% (n = 9), 40-50% (n = 6), 50-70% (n = 3) and > 70% (n = 2). No spontaneous embolisation was detected in either of the groups.

CONCLUSIONS

Transcranial Doppler generates reproducible data regarding the middle cerebral artery velocities. However, larger studies are needed to validate its clinical applicability.

TRIAL REGISTRATION

ClinicalTrial.gov (ID NCT 03050567), retrospectively registered on 15/05/2017.