Intraoperative transcranial Doppler: Limitations of the method

Eversion technique versus traditional carotid endarterectomy with patch angioplasty: a systematic review with meta-analyses and trial sequential analysis

Introduction

The use of an 'eversion' technique is not unequivocally proven to be superior to carotid endarterectomy with patch angioplasty. An up-to-date systematic review is needed for evaluation of benefits and harms of these two techniques.

Methods

RCTs comparing eversion technique versus endarterectomy with patch angioplasty in patients with a symptomatic and significant (≥50 %) stenosis of the internal carotid artery were enrolled. Primary outcomes were all-cause mortality rate, health-related quality of life and serious adverse events. Secondary outcomes included 30-day stroke and mortality rate, (a) symptomatic arterial occlusion or restenosis, and adverse events not critical for decision making.

Results

Four RCTs were included with 1272 surgical procedures for carotid stenosis; eversion technique n = 643 and carotid endarterectomy with patch closure n = 629. Meta-analysis comparing both techniques showed, with a very low certainty of evidence, that eversion technique might decrease the number of patients with serious adverse events (RR 0.47; 95% CI 0.34 to 0.64; p ≤ 0.01). However, no difference was found on the other outcomes. TSA demonstrated that the required information sizes were far from being reached for these patient-important outcomes. All patient-relevant outcomes were at low certainty of evidence according to GRADE.

Conclusions

This systematic review showed no conclusive evidence of any difference between eversion technique and carotid endarterectomy with patch angioplasty in carotid surgery. These conclusions are based on data obtained in trials with very low certainty according to GRADE and should therefore be interpreted cautiously. Until conclusive evidence is obtained, the standard of care according to ESVS guidelines should not be abandoned.

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.

Local versus general anaesthesia for carotid endarterectomy

BACKGROUND

Carotid endarterectomy may significantly reduce the risk of stroke in people with recently symptomatic, severe carotid artery stenosis. However, there are significant perioperative risks that may be minimised by performing the operation under local rather than general anaesthetics. This is an update of a Cochrane Review first published in 1996, and previously updated in 2004, 2008, and 2013.

OBJECTIVES

To determine whether carotid endarterectomy under local anaesthetic: 1) reduces the risk of perioperative stroke and death compared with general anaesthetic; 2) reduces the complication rate (other than stroke) following carotid endarterectomy; and 3) is acceptable to individuals and surgeons.

SEARCH METHODS

We searched CENTRAL, MEDLINE, Embase, and two trials registers (to February 2021). We also reviewed reference lists of articles identified.

SELECTION CRITERIA

Randomised controlled trials (RCTs) comparing the use of local anaesthetics to general anaesthetics for people having carotid endarterectomy were eligible.

DATA COLLECTION AND ANALYSIS

Three review authors independently extracted data, assessed risk of bias, and evaluated quality of evidence using the Grading of Recommendations, Assessment, Development, and Evaluations (GRADE) tool. We calculated a pooled Peto odds ratio (OR) and corresponding 95% confidence interval (CI) for the following outcomes that occurred within 30 days of surgery: stroke, death, ipsilateral stroke, stroke or death, myocardial infarction, local haemorrhage, and arteries shunted.

MAIN RESULTS

We included 16 RCTs involving 4839 participants, of which 3526 were obtained from the single largest trial (GALA). The main findings from our meta-analysis showed that, within 30 days of operation, neither incidence of stroke nor death were significantly different between local and general anaesthesia. Of these, the incidence of stroke in the local and general anaesthesia groups was 3.2% and 3.5%, respectively (Peto odds ratio (OR) 0.91, 95% confidence interval (CI) 0.66 to 1.26; P = 0.58; 13 studies, 4663 participants; low-quality evidence). The rate of ipsilateral stroke under both types of anaesthesia was 3.1% (Peto OR 1.03, 95% CI 0.71 to 1.48; P = 0.89; 2 studies, 3733 participants; low-quality evidence). The incidence of stroke or death in the local anaesthesia group was 3.5%, while stroke or death incidence was 4.1% in the general anaesthesia group (Peto OR 0.85, 95% CI 0.62 to 1.16; P = 0.31; 11 studies, 4391 participants; low-quality evidence). A lower rate of death was observed in the local anaesthetic group but evidence was of low quality (Peto OR 0.61, 95% CI 0.35 to 1.06; P = 0.08; 12 studies, 4421 participants).

AUTHORS' CONCLUSIONS

The incidence of stroke and death were not convincingly different between local and general anaesthesia for people undergoing carotid endarterectomy. The current evidence supports the choice of either approach. Further high-quality studies are still needed as the evidence is of limited reliability.

Carotid endarterectomy with patch angioplasty versus primary closure in patients with symptomatic and significant stenosis: a systematic review with meta-analyses and trial sequential analysis of randomized clinical trials

BACKGROUND

Patch angioplasty in conventional carotid endarterectomy is suggested to reduce the risk of restenosis and recurrent ipsilateral stroke compared with primary closure. A systematic review of randomized clinical trials is needed to compare outcomes (benefits and harms) of both techniques.

METHODS

Searches (CENTRAL, PubMed/MEDLINE, EMBASE, and other databases) were last updated 3rd of January 2021. We included randomized clinical trials comparing carotid endarterectomy with patch angioplasty versus primary closure of the arterial wall in patients with a symptomatic and significant (> 50%) carotid stenosis. Primary outcomes are defined as all-cause mortality and serious adverse events.

RESULTS

We included 12 randomized clinical trials including 2187 participants who underwent 2335 operations for carotid stenosis comparing carotid endarterectomy with patch closure (1280 operations) versus carotid endarterectomy with primary closure (1055 operations). Meta-analysis comparing carotid endarterectomy with patch angioplasty versus carotid endarterectomy with primary closure may potentially decrease the number of patients with all-cause mortality (RR 0.53; 95% CI 0.26 to 1.08; p = 0.08, best-case scenario for patch), serious adverse events (RR 0.73; 95% CI 0.56 to 0.96; p = 0.02, best-case scenario for patch), and the number of restenosis (RR 0.41; 95% CI 0.23 to 0.71; p < 0.01). Trial sequential analysis demonstrated that the required information sizes were far from being reached for these patient-important outcomes. All the patient-relevant outcomes were at low certainty of evidence according to The Grading of Recommendations Assessment, Development, and Evaluation.

CONCLUSIONS

This systematic review showed no conclusive evidence of a difference between carotid endarterectomy with patch angioplasty versus primary closure of the arterial wall on all-cause mortality, < 30 days mortality, < 30 days stroke, or any other serious adverse events. These conclusions are based on data from 15 to 35 years ago, obtained in trials with very low certainty according to GRADE, and should be interpreted cautiously. Therefore, we suggest conducting new randomized clinical trials patch angioplasty versus primary closure in carotid endarterectomy in symptomatic patients with an internal carotid artery stenosis of 50% or more. Such trials ought to be designed according to the Standard Protocol Items: Recommendations for Interventional Trials statement (Chan et al., Ann Intern Med 1:200-7, 2013) and reported according to the Consolidated Standards of Reporting Trials statement (Schulz et al., 7, 2010). Until conclusive evidence is obtained, the standard of care according to guidelines should not be abandoned.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42014013416 . Review protocol publication 2019 DOI: https://doi.org/10.1136/bmjopen-2018-026419 .

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.

Role of Resistivity Index Analysis in the Prediction of Hemodynamically Significant Venous Sinus Stenosis in Patient With Idiopathic Intracranial Hypertension

BACKGROUND

The resistivity index (RI) in cerebral venous sinus stenosis (VSS) has not been studied in patients with idiopathic intracranial hypertension (IIH).

OBJECTIVE

To evaluate the role of RI measured by quantitative magnetic resonance venogram (QMRV) as a noninvasive tool in the diagnosis of venous hypertension associated with VSS in IIH.

METHODS

Retrospective evaluation of 13 consecutive IIH patients who underwent venous sinus stenting at our institution between 2013 and 2018.

Patients’ demographics, clinical presentation, cerebral mean venous sinus pressure (MVP), and RI both pre- and poststenting were recorded. The baseline RI was also compared to a control group.

RESULTS

Among 13 patients of IIH, 11 had unilateral VSS in dominant sinus, whereas 2 had bilateral VSS. RI was significantly higher in IIH patients compared to the control group in the superior sagittal (SSS) and transverse sinuses (TS) (0.21 vs 0.11, P = .01 and 0.22 vs 0.13, P = .03, respectively). The MVP (in mm Hg) decreased significantly after venous sinus stenting in the SSS (41.9 to 22.5, P &lt; .001) and TS (39.4 to 19.5, P &lt; .001), which was also associated with a significant reduction of the RI (0.22 vs 0.17, P &lt; .01 in SSS and 0.23 vs 0.17, P = .03 in TS) poststenting.

CONCLUSION

RI calculated using QMRV can serve as a noninvasive tool to aid in the diagnosis of hemodynamically significant VSS. The study had a small sample size, and larger multicenter studies would be required to validate the results further.

Quantitative analysis of the effect of end-tidal carbon dioxide on regional cerebral oxygen saturation in patients undergoing carotid endarterectomy under general anaesthesia

AIMS

Regional cerebral oxygen saturation (rSO₂ ) is currently the most used measure in clinical practice to monitor cerebral ischaemia in patients undergoing carotid endarterectomy (CEA). Although end-tidal carbon dioxide (P_ET CO₂ ) is known as a factor that influences rSO₂ , the relationship between P_ET CO₂ and rSO₂ has not been quantitatively evaluated in patients with severe arteriosclerosis. This study aimed to evaluate the effect of P_ET CO₂ on rSO₂ in patients undergoing CEA under general anaesthesia.

METHODS

The intervention to change P_ET CO₂ was conducted between skin incision and clamping of the carotid artery. The rSO₂ values were observed by changing P_ET CO₂ in the range of 25-45 mmHg. The P_ET CO₂ -rSO₂ relationship was characterized by population analysis using a turnover model.

RESULTS

In total, 1651 rSO₂ data points from 30 patients were used to determine the pharmacodynamic characteristics. Hypertension (HTN) and systolic blood pressure (SBP) were significant covariates on the slope factor in the stimulatory effect of P_ET CO₂ on rSO₂ and fractional turnover rate constant (k_out ), respectively. The estimates of the parameters were k_out (min^-1 ): 3.59 for SBP <90 mmHg and 0.491 for SBP ≥90 mmHg, slope: 0.00321 for patients with HTN and 0.00664 for patients without HTN.

CONCLUSION

The presence of HTNattenuates the response of rSO₂ after a change in P_ET CO₂ . When cerebral blood flow is in a state of decline caused by a decrease in SBP to <90 mmHg, the response of rSO₂ to P_ET CO₂ is increased. It is advisable to maintain SBP >90 mmHg in patients with HTNduring CEA.

Carotid Angioplasty and Stenting: Will Periprocedural Transcranial Doppler Monitoring Be Important?

Purpose:

To explore the value of transcranial Doppler (TCD) ultrasonography in the periprocedural monitoring of patients undergoing angioplasty procedures for stenosis of the internal carotid artery.

Methods:

Thirty-two patients were included in the study between April 1991 and September 1995 (6 females, 26 males; average age 66 years). All patients were interrogated before and after angioplasty by a standard TCD examination protocol. Intraprocedurally, TCD was used continuously to monitor cerebral blood flow and supply evidence of embolic particulates. Nineteen patients were treated by percutaneous transluminal angioplasty (PTA) alone; the other 13 underwent primary stent (PS) implantation.

Results:

High-intensity transient signals indicative of emboli appeared to be more frequent in the PTA group than in the PS cohort. Preoperative TCD identified 3 (9%) high-risk patients with incompetent collateral pathways through the circle of Willis. Intraoperatively, TCD detected two postdilation carotid occlusions, a sylvian embolism, and one case of arterial spasm. The preprocedural TCD in a patient with contralateral carotid occlusion showed good collateral circulation, providing reassurance during conversion to endarterectomy when an undeployed stent obstructed blood flow. Postoperatively, TCD confirmed restored intracerebral circulation and identified one hyperperfusion syndrome.

Conclusions:

TCD is a simple, relatively inexpensive examination that can preprocedurally identify carotid stenosis patients at high risk for intraoperative cerebral ischemia in whom PTA might be preferable to surgery. During the procedure, TCD can document the benefits of endovascular treatment and offer early detection of ischemic complications.

Local versus general anaesthesia for carotid endarterectomy

BACKGROUND

Carotid endarterectomy may significantly reduce the risk of stroke in people with recently symptomatic, severe carotid artery stenosis. However, there are significant perioperative risks that may be reduced by performing the operation under local rather than general anaesthetic. This is an update of a Cochrane Review first published in 1996, and previously updated in 2004 and 2008.

OBJECTIVES

To determine whether carotid endarterectomy under local anaesthetic: (1) reduces the risk of perioperative stroke and death compared with general anaesthetic; (2) reduces the complication rate (other than stroke) following carotid endarterectomy; and (3) is acceptable to patients and surgeons.

SEARCH METHODS

We searched the Cochrane Stroke Group Trials Register (September 2013), MEDLINE (1966 to September 2013), EMBASE (1980 to September 2013) and Index to Scientific and Technical Proceedings (ISTP) (1980 to September 2013). We also handsearched relevant journals, and searched the reference lists of articles identified.

SELECTION CRITERIA

Randomised trials comparing the use of local anaesthetic to general anaesthetic for carotid endarterectomy were considered for inclusion.

DATA COLLECTION AND ANALYSIS

Three review authors independently assessed trial quality and extracted data. We calculated a pooled Peto odds ratio (OR) and corresponding 95% confidence interval (CI) for the following outcomes that occurred within 30 days of surgery: stroke, death, stroke or death, myocardial infarction, local haemorrhage, cranial nerve injuries, and shunted arteries.

MAIN RESULTS

We included 14 randomised trials involving 4596 operations, of which 3526 were from the single largest trial (GALA). In general, reporting of methodology in the included studies was poor. All studies were unable to blind patients and surgical teams to randomised treatment allocation and for most studies the blinding of outcome assessors was unclear. There was no statistically significant difference in the incidence of stroke within 30 days of surgery between the local anaesthesia group and the general anaesthesia group. The incidence of strokes in the local anaesthesia group was 3.2% compared to 3.5% in the general anaesthesia group (Peto OR 0.92, 95% CI 0.67 to 1.28). There was no statistically significant difference in the proportion of patients who had a stroke or died within 30 days of surgery. In the local anaesthesia group 3.6% of patients had a stroke or died compared to 4.2% of patients in the general anaesthesia group (Peto OR 0.85, 95% CI 0.63 to 1.16). There was a non-significant trend towards lower operative mortality with local anaesthetic. In the local anaesthesia group 0.9% of patients died within 30 days of surgery compared to 1.5% of patients in the general anaesthesia group (Peto OR 0.62, 95% CI 0.36 to 1.07). However, neither the GALA trial or the pooled analysis were adequately powered to reliably detect an effect on mortality.

AUTHORS' CONCLUSIONS

The proportion of patients who had a stroke or died within 30 days of surgery did not differ significantly between the two types of anaesthetic techniques used during carotid endarterectomy. This systematic review provides evidence to suggest that patients and surgeons can choose either anaesthetic technique, depending on the clinical situation and their own preferences.

Cerebral hemodynamics and incident depression: the Rotterdam Study

BACKGROUND

According to the vascular depression hypothesis, subclinical cerebrovascular disease can cause depression in older adults. To test this hypothesis, several cross-sectional studies have assessed structural brain parameters, but few have examined hemodynamic alterations in the brain.

METHODS

From the Rotterdam Study, we studied a cohort of 1494 participants (65+ years of age) free of depression, dementia, and stroke at baseline. In the middle cerebral artery blood flow velocities and vasomotor reactivity were measured with transcranial Doppler ultrasonography. All participants were repeatedly assessed for depressive symptoms with Centre for Epidemiological Studies-Depression scale (CES-D). Participants with depressive symptoms (CES-D ≥16) had a semi-structured interview, to classify the depression according to DSM-IV criteria. All analyses were adjusted for sociodemographic data, vascular risk factors, and incident stroke.

RESULTS

Lower peak-systolic, end-diastolic, and mean blood flow velocities at baseline were associated with higher CES-D scale scores at follow-up. Mean blood flow velocity predicted incident depressive symptoms (odds ratio [OR]: .74, 95% confidence interval [CI]: .60-.91, p = .004) and depressive disorders (OR: .83, 95% CI: .69-.98, p = .032), whereas decreased baseline vasomotor reactivity predicted incident depressive disorders only (OR: .66, 95% CI: .53-.83, p < .001).

CONCLUSIONS

Lower blood flow velocity, indicating reduced cerebral metabolism, predicted depressive symptoms and depressive disorders. Reduced vasomotor reactivity, which might indicate cerebral microangiopathy, predicted depressive disorders only, in healthy older adults. These findings provide prospective evidence for vascular depression hypothesis.

Perioperative transorbital Doppler flow imaging offers an alternative to transcranial Doppler monitoring in those patients without a temporal bone acoustic window

Transcranial Doppler has been used to identify microembolic signals before, during and after carotid endarterectomy, but 10% to 15% of patients are reported not to have suitable temporal bone window. The aim of this study was to assess the feasibility of transorbital Doppler monitoring of patients with absent temporal bone acoustic window. Between 2005 and 2008, those patients with absent temporal bone acoustic window were assessed for a transorbital acoustic window. During the study period, 318 carotid endarterectomy were performed. In the 29 (9.1%) with absent temporal bone acoustic window, 25 (86%) had satisfactory transorbital acoustic windows, consequently only four (1.2%) of patients could not be monitored postoperatively. One patient required postoperative transorbital acoustic windows directed glycoprotein IIb/IIIa receptor antagonist infusion due to excessive carotid microembolisation to prevent stroke. This is the first description of the use of transorbital flow imaging to determine postoperative cerebral blood flow, microembolic load and to direct the use of intravenous antiplatelet agents.

Local versus general anaesthesia for carotid endarterectomy

BACKGROUND

Carotid endarterectomy reduces the risk of stroke in people with recently symptomatic, severe carotid artery stenosis. However, there are significant perioperative risks which may be lessened by performing the operation under local rather than general anaesthetic. This is an update of a Cochrane review first published in 1996, and previously updated in 2004.

OBJECTIVES

To assess the risks of endarterectomy under local compared with general anaesthetic.

SEARCH STRATEGY

We searched the Cochrane Stroke Group Trials Register (last searched December 2007), MEDLINE (1966 to April 2007) EMBASE (1980 to April 2007) and Index to Scientific and Technical Proceedings (ISTP, 1980 to April 2007). We also handsearched six relevant journals to April 2007, and searched the reference lists of articles identified. For the previous version of this review we handsearched a further seven journals to 2002 and in August 2001 advertised the review in Vascular News, a newspaper for European vascular specialists.

SELECTION CRITERIA

Randomised trials and non-randomised studies comparing carotid endarterectomy under local versus general anaesthetic.

DATA COLLECTION AND ANALYSIS

Two review authors assessed trial quality and extracted the data independently.

MAIN RESULTS

Nine randomised trials involving 812 operations, and 47 non-randomised studies involving 24,181 operations were included. Meta-analysis of the randomised studies showed that there was no evidence of a reduction in the odds of operative stroke, but the use of local anaesthetic was associated with a significant reduction in local haemorrhage (odds ratio 0.30, 95% confidence interval 0.12 to 0.77) within 30 days of the operation. However, the randomised trials were too small to allow reliable conclusions to be drawn, and in some studies intention-to-treat analyses were not possible because of exclusions. Meta-analsis of the non-randomised studies showed that the use of local anaesthetic was associated with significant reductions in the odds of stroke (38 studies), death (42 studies), stroke or death (27 studies), myocardial infarction (27 studies), and pulmonary complications (seven studies), within 30 days of the operation. The methodological quality of the non-randomised trials was questionable. Thirteen of the non-randomised studies were prospective and 36 reported on a consecutive series of patients. In eleven non-randomised studies the number of arteries, as opposed to the number of patients, was unclear.

AUTHORS' CONCLUSIONS

There is insufficient evidence from randomised trials comparing carotid endarterectomy performed under local and general anaesthetic. Non-randomised studies suggest potential benefits with the use of local anaesthetic, but these studies may be biased.

Comparison of monitoring techniques for intraoperative cerebral ischemia

OBJECTIVE

To prospectively compare somatosensory evoked potentials, electroencephalography (EEG) and transcranial Doppler ultrasound (TCD) for detection of cerebral ischemia during carotid endarterectomy (CEA).

METHODS

Somatosensory evoked potentials and EEG recordings were attempted in 156 consecutive CEAs and TCD was also attempted in 91 of them. Recordings from all three modalities were obtained for at least 10 minutes before CEA, during CEA and for at least 15 minutes after CEA. Somatosensory evoked potentials peak-to-peak amplitude decrease of >50%, EEG amplitude decrease of >75%, and ipsilateral middle cerebral artery mean blood flow velocity (mean VMCAi) decrease >75% persisting for the entire period of internal carotid artery occlusion were individually considered to be diagnostic of cerebral ischemia. Clinical neurological examination was performed immediately prior to surgery and following recovery from general anaesthesia.

RESULTS

Somatosensory evoked potentials, EEG, and TCD were successfully obtained throughout the entire period of internal carotid artery occlusion in 99%, 95%, and 63% of patients respectively. Two patients (1.3%) suffered intraoperative cerebral infarction detected by clinical neurological examination and subsequent magnetic resonance imaging. Somatosensory evoked potentials accurately predicted intraoperative cerebral infarction in both instances without false negatives or false positives, EEG yielded one false negative result and no false positive results and VMCAi one true positive, four false positive and no false negative results. Transcranial Doppler ultrasound detection of emboli did not correlate with postoperative neurological deficits. Nevertheless the sensitivity and specificity of each test was not significantly different than the others because of the small number of disagreements between tests.

CONCLUSION

A >50% decrease in the cortically generated P25 amplitude of the median somatosensory evoked potentials, which persisted during the entire period of internal carotid artery occlusion, appears to be the most reliable method of monitoring for intraoperative ischemia in our hands because it accurately detected both intraoperative strokes with no false positive or false negative results.

Local versus general anaesthesia for carotid endarterectomy

BACKGROUND

Carotid endarterectomy reduces the risk of stroke in people with recently symptomatic, severe carotid artery stenosis. However, there are significant perioperative risks which may be lessened by performing the operation under local rather than general anaesthetic.

OBJECTIVES

The aim of this review was to assess the risks of endarterectomy under local compared with general anaesthetic.

SEARCH STRATEGY

We searched the Stroke Group trials register (April 2003), MEDLINE (1966 to April 2003), EMBASE (1980 to 2002), and Index to Scientific and Technical Proceedings (1980 to 1994). We handsearched 13 relevant journals up to 2002, and searched the reference lists of articles identified. We also advertised the review in Vascular News (a newspaper for European vascular specialists) in August 2001.

SELECTION CRITERIA

Randomised trials and non-randomised studies comparing carotid endarterectomy under local versus general anaesthetic.

DATA COLLECTION AND ANALYSIS

One reviewer selected studies for inclusion and another independently checked the decisions. Two reviewers assessed trial quality and independently extracted the data.

MAIN RESULTS

Seven randomised trials involving 554 operations, and 41 non-randomised studies involving 25622 operations were included. The methodological quality of the non-randomised trials was questionable. Eleven of the non-randomised studies were prospective and 29 reported on a consecutive series of patients. In nine non-randomised studies the number of arteries, as opposed to the number of patients, was unclear. Meta-analysis of the non-randomised studies showed that the use of local anaesthetic was associated with significant reductions in the odds of death (35 studies), stroke (31 studies), stroke or death (26 studies), myocardial infarction (22 studies), and pulmonary complications (7 studies), within 30 days of the operation. Meta-analysis of the randomised studies showed that the use of local anaesthetic was associated with a significant reduction in local haemorrhage (OR = 0.31, 95% CI = 0.12 to 0.79) within 30 days of the operation, but there was no evidence of a reduction in the odds of operative stroke. However, the trials were too small to allow reliable conclusions to be drawn, and in some studies intention-to-treat analyses were not possible because of exclusions.

REVIEWERS' CONCLUSIONS

There is insufficient evidence from randomised trials comparing carotid endarterectomy performed under local and general anaesthetic. Non-randomised studies suggest potential benefits with the use of local anaesthetic, but these studies may be biased. More randomised studies are needed.

Physiological advantages of cerebral blood flow during carotid endarterectomy under local anaesthesia. A randomised clinical trial

OBJECTIVE

to examine the effects of type of anaesthesia on cerebral blood flow during carotid endarterectomy (CEA).

DESIGN

prospective randomised study.

METHODS

thirty-four CEA procedures under local anaesthesia (LA) are compared to 33 procedures under general anaesthesia (GA). Mean middle cerebral artery velocity (MCAV(mean)) was monitored using Transcranial Doppler (TCD) and mean arterial pressure (MAP) assessed by continuous intra-arterial blood pressure transducer.

RESULTS

pre-op MCAV(mean) and MAP were similar in both groups. Pre-clamp MCAV(mean) was similar in both groups and did not differ from pre-op values. With carotid clamping the MCAV(mean) significantly dropped in both groups. The post-clamp MCAV(mean) was significantly less in the GA group (p < 0.05), and the percentage reduction in MCAV(mean) significantly more for GA procedures (p < 0.05). Pre-clamp MAP was significantly elevated in LA procedures and significantly lowered in GA procedures. Pre-clamp MAP was significant less for GA procedures (p < 0.001). Post clamp MAP did not differ from pre-clamp levels in either group. There was no correlation between MCAV(mean) and MAP. Complication rate, combined death/stroke rates were similar in each group.

CONCLUSION

LA CEA is associated with better preservation of the ipsilateral cerebral circulation and increased tolerance of the effects of carotid clamping. Changes in MCAV(mean) cannot be explained by variations in blood pressure between the two techniques.

Middle cerebral artery circulation during carotid surgery. A transcranial Doppler study

OBJECTIVE

Perioperative carotid cross-clamping might induce low stump pressures as well as hypoperfusion of the middle cerebral artery. In this study blood flow velocities in the middle cerebral artery were compared with intraoperative measurements of the poststenotic carotid blood pressure.

DESIGN

Forty-one patients with internal carotid artery stenosis were operated on without shunting, under general anesthesia. Poststenotic carotid pressures and middle cerebral artery flow velocities were measured before and during cross-clamping. The hemodynamic responses to preoperative carotid compressions and intraoperative cross-clamping were evaluated.

RESULTS

In seven patients the poststenotic carotid blood pressure decreased on clamping despite unchanged or even increased middle cerebral artery blood flow velocities. In all other patients, pressure changes were significantly correlated to the decrease in middle cerebral artery blood flow velocities. Autoregulatory blood flow velocity responses after preoperative common carotid artery compression were not reproducible by cross-clamping.

CONCLUSIONS

Stump blood pressure measurements may not reflect middle cerebral artery perfusion in about 20% of thrombendarterectomies performed under general anesthesia. A possible explanation might be dimished cerebral autoregulation and changes in collateral flow distributions.

Hemodynamic evaluation by using near infrared spectroscopy during carotid endarterectomy

To evaluate the hemodynamic changes during carotid endarterectomy, we compared changes in oxyhemoglobin levels with changes in the internal carotid artery flow and the somatosensory evoked potential (SEP). In 40 of 42 patients, the oxyhemoglobin level, measured in the frontal area on the operated side using near infrared spectroscopy (NIRS), decreased immediately after cross-clamping the internal carotid artery and returned to the preclamping level after the clamp was removed. There was no linear relationship between the internal carotid flow and the decrement in the oxyhemoglobin level after carotid clamping. Nineteen patients (45%) had a large internal carotid flow (> or =90 mL/min), but a small decrease in the oxyhemoglobin level (<0.04 in index); presumably these patients had adequate collateral circulation. Eight patients (19%) had a large internal carotid flow and a marked decrease in the oxyhemoglobin level (> or =0.04); presumably these patients had insufficient collateral circulation. The changes in oxyhemoglobin and SEP after carotid clamping agreed in 77.5% of the patients; however, in the other 22.5%, the disparity between the two factors indicated different causes of cerebral ischemia following carotid clamping. A marked decrease in oxyhemoglobin without a significant change in SEP suggests ischemia predominantly in the frontal area, whereas a small decrease in oxyhemoglobin and a significant change in SEP suggest ischemia predominantly in the somatosensory pathway or cortex. In conclusion, the relationship between the internal carotid flow and the change in HbO(2) provides information about the collateral circulation. Simultaneous monitoring of NIRS and SEP is useful for assessing of the pattern of cerebral ischemia during carotid clamping.

Continuous intraoperative monitoring of middle cerebral artery blood flow velocities and electroencephalography during carotid endarterectomy. A comparison of the two methods to detect cerebral ischemia

BACKGROUND AND PURPOSE

Intraoperative monitoring of brain function may influence the outcome of carotid endarterectomy (CEA).

METHODS

We performed transcranial Doppler (TCD) monitoring of middle cerebral artery blood flow velocities (VMCAs) and eight-channel electroencephalographic (EEG) recording simultaneously in 82 patients undergoing CEA. Thiopental narcosis limited EEG interpretation in 11 patients, thus allowing direct comparison of both methods in 71 patients.

RESULTS

There was a significant correlation between VMCA decrease and the frequency of EEG changes after carotid clamping (P < .001). Eight patients (11%) showed a VMCA decrease exceeding 60%, accompanied by EEG changes in 7 patients. Altogether, 16 patients (22%) showed severe or moderate EEG changes. Stenosis or occlusion of the contralateral carotid artery led to an increase of abnormal findings with both monitoring methods, which was, however, significant only for TCD (P < .05). Four patients (4.8%) suffered intraoperative transient ischemic attacks. In 3 of these patients, there were no abnormal findings with either of the methods. The events were thus unpredictable and probably of embolic origin. The fourth patient showed VMCA decrease to 0 and severe EEG changes. Nine patients had severe or moderate EEG changes without significant VMCA decrease and without complications. EEG monitoring alone in these would have led to unnecessary use of a shunt with the increased risk of embolism.

CONCLUSION

EEG and TCD monitoring are complementary techniques. Their results showed a good overall correlation but with marked differences in the individual patient. TCD monitoring alone was sensitive enough to prevent ischemic intraoperative complications. EEG findings are of limited value when barbiturates are used.

Intraoperative transcranial Doppler sonography monitoring during carotid surgery under locoregional anaesthesia

OBJECTIVES

Studies comparing transcranial Doppler ultrasonography (TCD) with other intraoperative monitoring techniques for detecting clamping ischaemia during carotid endarterectomy under general anaesthesia suggest that a reduction of > two-thirds in the mean middle cerebral artery velocity (mMCAv) or a reduction of > 0.4 in the preclamping mMCAv: clamping mMCAv ratio warrants cerebral protection. Our aim was to study the relationship between mMCAvs and clamping ischaemia during carotid endarterectomy in awake patients.

MATERIALS AND METHODS

In a consecutive series of 57 patients undergoing carotid endarterectomy under locoregional anaesthesia 51 were monitored by intraoperative TCD, continuous EEG, and neurologic awake testing.

RESULTS

Five of the 51 (9.8%) patients had transient clamping ischaemia, which carotid shunting reversed. TCD showed that these five patients had significant lower mean mMCAvs than the other 46 patients, who had no deficits (1.8 +/- 1.1 cm/s vs. 26.2 +/- 8.5, p = 0.0003). Current TCD criteria indicated that four other patients (7.8%) should have been shunted. All four had significantly higher clamping mMCAvs than the five shunted patients (11.5 +/- 1.9 vs. 1.8 +/- 1.1, p = 0.0012).

CONCLUSIONS

Intraoperative TCD detected cerebral ischaemia and yielded no false-negative. An mMCAv of 10 cm/s or less may indicate the risk of clamping ischaemia better than the higher threshold currently proposed. This would avoid unnecessary shunting due to false-positives.

Arterial pressure and neurologic morbidity during carotid surgery under peridural anesthesia

In 163 carotid reconstructions under peridural anesthesia performed from 1988 to 1991, we routinely measured residual systemic and carotid artery pressure during clamping. Seventy-nine patients (48.5%) were asymptomatic and 84 (51.5%) had a history of neurologic manifestations in the form of transient ischemic attacks (28%) or stroke (13.5%). None of the patients died perioperatvely. Eight patients (4.9%) had strokes, with complete recovery in five. A shunt was placed in 22 patients (13.5%) because of neurologic evidence that carotid clamping was poorly tolerated. This study showed a distinct association between residual pressure in the internal carotid artery and systemic arterial pressure and intraoperative neurologic morbidity. Using a cutoff value of 35 mm Hg for residual pressure, the sensitivity was 77% and specificity 81%. Using a cutoff of 80 mm Hg, the sensitivity was 60% and specificity 86%. There was no correlation between mean systemic arterial pressure and residual carotid artery pressure. The use of a shunt was the only factor with predictive value for postoperative neurologic complications. These findings suggest that measurement of systemic arterial pressure and residual carotid artery pressure is useful during carotid surgery, but further study is needed before this information can be extrapolated to carotid surgery under general anesthesia.

The role of intraoperative transcranial Doppler monitoring in carotid artery surgery

Of 135 carotid artery reconstructions performed under general anesthesia in 127 patients (mean age 68 years), 119 were performed with continuous intraoperative Doppler recording of the middle cerebral artery. This investigation was impossible in nine (6.7%) cases because of the absence of a visible temporal window, and results were deemed uninterpretable in six (4.5%) additional cases. The goals of this study were to test the feasibility and reliability of transcranial Doppler monitoring in the evaluation of intracranial perfusion and to determine the risk of cerebral ischemia during carotid artery clamping. The two outcome parameters measured were mean velocity and percentage of decreased flow in the middle cerebral artery during clamping. Patients were divided into four groups based on variations in these parameters. Groups I and IIA (low risk) represented 69.7% of cases, group IIB (significant risk) represented 21.9%, and group III (major risk) represented 8.4%. Transcranial Doppler monitoring appears to be a reliable means of observing middle cerebral artery flow during carotid surgery and in our opinion provides objective criteria for determining the need for an indwelling shunt. Accordingly, in this study no neurologic complications imputable to clamping were observed. Transcranial Doppler monitoring can also be used to ensure correct functioning of the shunt and to detect intraoperative embolic complications.

Cerebral oxygen saturation, transcranial Doppler ultrasonography and stump pressure in carotid surgery

Transcranial Doppler ultrasonography (TCD) of the middle cerebral artery (MCA), light-reflective cerebral oximetry and measurement of internal carotid artery stump pressure were compared as methods of monitoring cerebral perfusion during carotid surgery in 33 patients. Median cerebral oxygen saturation was 70 (range 62-85) per cent and TCD-measured mean blood velocity 42 (range 19-91) cm/s before carotid cross-clamping, falling to 68 (53-83) per cent and 16 (0-50) cm/s respectively on application of the clamps (P < 0.001). Stump pressure correlated closely with MCA blood velocity 30 s after the start of cross-clamping (rs = 0.58, P < 0.001), but not with cerebral oxygen saturation. A fall of 5 per cent or more in cerebral oxygen saturation following cross-clamp application was predicted by a decrease in mean MCA blood velocity of at least 60 per cent. Changes in cerebral oxygen saturation correlated significantly with systolic blood pressure throughout the perioperative period (rs = 0.41, P < 0.001). Significant falls in cerebral oxygenation were not predicted by low stump pressure but were associated with large reductions in the mean MCA blood velocity measured by TCD.

Carotid endarterectomy in awake patients: its safety, acceptability, and outcome

PURPOSE

The purpose of this study was to determine the safety and efficacy of performing carotid endarterectomy procedures with the patient receiving cervical block anesthetic.

METHODS

Over the last 14 years, 654 carotid endarterectomy procedures were performed with patients receiving regional anesthetic. Intraluminal shunts were placed on demand, if neurologic changes with clamping of the carotid artery developed in the patient. During the same period, 419 cases were done with the patients receiving general anesthetic. Choice of anesthetic was based on surgeon and patient preference.

RESULTS

In the regional anesthetic group the indications for operation included transient ischemic attack (311), asymptomatic hemodynamically significant stenosis (146), amaurosis fugax (106), stroke (86), restenosis (3), and aneurysm (2). Shunts were used in 46 of 654 cases (7%). Conversion from regional to general anesthetic was required in seven patients (1.1%). The operative mortality rate was 0.76% (5 of 654). Permanent nonfatal neurologic deficits occurred in 0.76% (5 of 654), and temporary neurologic deficits occurred in 1.07% (7 of 654).

CONCLUSIONS

On the basis of these results, we believe regional cervical block anesthetic is an acceptable option to the routine use of shunts performed with the patient receiving general anesthetic during carotid endarterectomy. In addition, the ability to continuously assess the awake patient receiving cervical block may contribute to a decrease in perioperative stroke and mortality rates while simplifying functional cerebral monitoring during carotid endarterectomy.

Blood flow velocity in the middle cerebral artery and carotid artery stump pressure during carotid endarterectomy

Twenty-one patients undergoing carotid endarterectomy were investigated by simultaneous intra-operative measurements of carotid stump pressure (CSP) and transcranial Doppler (TCD) flow velocity in the middle cerebral artery. The relationship between the two methods was evaluated as well as the potential benefits of the intraoperative transcranial Doppler monitoring technique. Clamping of the carotid artery resulted in a significant decrease in TCD flow velocity in the ipsilateral middle cerebral artery as well as in CSP. There was no correlation between relative change in CSP and the simultaneously obtained relative change in TCD flow velocity during carotid clamping (r = 0.31, p = 0.26). The insertion of an intra-operative shunt was followed by an increase in flow velocity compared to the clamping value. One patient with clear TCD signs of a re-occlusion (a sudden decrease in flow velocity) during closure of the wound, demonstrated a thrombosis at re-exploration. TCD gives information of the collateral cerebral circulation during carotid clamping and is an alternative monitoring technique during carotid endarterectomy. The method is useful intraoperatively for detecting embolic events as well as thrombosis during wound closure. Further studies are necessary to clarify the critical change in flow velocity during clamping when the use of a peroperative shunt is indicated.

EEG monitoring of carotid endarterectomy with routine patch-graft angioplasty: an experience in a large series

Four hundred and thirty-nine carotid endarterectomies (CEAs) with routine use of patchgraft angioplasty were performed in 375 patients; the indwelling shunt was used only in patients showing clamp-related EEG abnormalities. Five patients showed EEG abnormalities just after head positioning, which reversed after removal of head hyperextension; three cases suffered EEG flattening due to severe bradycardia or cardiac arrest before carotid clamping, which promptly reversed after treatment. Clamp-related EEG abnormalities appeared in 106 operations (24.2%) and all reversed after the insertion of the indwelling shunt; patients with occlusion of the contralateral internal carotid artery showed a 68.8% rate of EEG clamp-related changes. The short term follow-up (one month after the operation) showed six minor strokes with complete recovery (1.37%), one intraoperative stroke (0.23%), three delayed major strokes (0.69%) and three neurological deaths (0.69%). The long-term follow-up over an average of 42 months showed a 3.7% rate of relevant neurological complications (ie permanent deficits + death) and a 3.16% rate significant restenosis or occlusion of the operated carotid artery. Our results show that the routine use of EEG monitoring and patch-graft angioplasty allow to perform CEAs with a very high degree of safety, improving the clinical course of the disease.

Risks and benefits of shunting in carotid endarterectomy. The International Transcranial Doppler Collaborators

BACKGROUND AND PURPOSE

Controversy continues about the pathogenesis of perioperative stroke in carotid endarterectomy and the use of shunting. The purpose of this study was to determine, using transcranial Doppler ultrasonography, the severity of ischemia during clamping of the carotid artery as a basis for analysis of complications in patients operated on with and without shunting.

METHODS

In a retrospective study, 11 centers contributed 1,495 carotid endarterectomies monitored with transcranial Doppler. The cases were divided into groups with severe, mild, and no ischemia, and each group was subdivided according to shunt use. The perioperative rate of severe stroke attributable to intraoperative ischemia, in addition to total perioperative stroke, was determined for each subgroup.

RESULTS

Severe ischemia occurred in 7.2% of our cases but cleared spontaneously in about half of these. In those with persisting ischemia the rate of severe stroke was very high, while shunting protected against stroke in such cases. If ischemia did not occur, the stroke rate was higher with shunting, although not so high as in unshunted cases with severe ischemia. Slightly more than one third of the severe strokes were due to postoperative cerebral hemorrhage or carotid thrombosis, unrelated to clamp-induced ischemia or shunting.

CONCLUSIONS

Carotid endarterectomy complications might be reduced by selectively shunting only for severe persisting ischemia. Monitoring of cerebral ischemia would be essential to selective shunting.

Relation between middle cerebral artery blood flow velocity and stump pressure during carotid endarterectomy

BACKGROUND AND PURPOSE

Many patient monitoring techniques have been used for detecting cerebral hypoperfusion during carotid endarterectomy. We compared middle cerebral artery blood flow velocities with carotid artery stump pressures to evaluate the indications for common carotid artery cross-clamp shunting and the probable hemodynamic causes of cerebrovascular complications.

METHODS

Blood flow velocities were monitored with transcranial Doppler ultrasound and carotid stump pressures were measured at the time of common carotid artery cross-clamping during 97 carotid endarterectomy procedures. Stump pressures measured with the gauge zero reference at the common carotid artery level were correlated with the percentage change of velocities.

RESULTS

Middle cerebral artery blood flow velocities usually decreased upon common carotid artery cross-clamping, depending on collateral availability and the autoregulation response. The best fit of the data was to an exponential function concave to the pressure axis, with velocity as a percentage of the pre-cross-clamp value reaching zero at 15 mm Hg stump pressure (r = 0.85 and p less than 0.001).

CONCLUSIONS

There is a less critical margin of error with percentage middle cerebral artery blood flow velocity decreases than with stump pressure measurements. This relation establishes changes in middle cerebral artery blood flow velocities as a reliable parameter for judging the effects of carotid cross-clamping on cerebral blood flow and providing an excellent indicator as to the necessity for shunting.

Transcranial Doppler for detection of cerebral ischaemia during carotid endarterectomy

We evaluated transcranial Doppler sonography (TCD) for the detection of cerebral ischaemia during carotid endarterectomy in 30 male and 14 female patients with ipsilateral focal cerebro-vascular symptoms. Surgery was performed during halothane-nitrous oxide anaesthesia with moderate hypocapnia. Eight patients had a temporary shunt owing to contralateral occlusion or a stump pressure below 40 mmHg, and/or EEG flattening. Transcranial Doppler sonography was followed intra-operatively together with electro-encephalography (EEG), internal carotid artery (ICA) pressures and cerebral blood flow (CBF). Middle cerebral artery mean flow velocity (Vmean) was 38 (22-96) cm s-1 (median and range) and decreased during cross-clamping to 28 (10-60) cm s-1 (p less than 0.0001). After removal of the clamp it increased to 42 (20-102) cm s-1 (p less than 0.0001). AVmean clamp of less than 30 cm s-1 together with a Vmean clamp: Vmean pre-clamp ratio of less than 0.6 showed an accuracy with respect to CBF below 20 ml 100 g-1 min-1 of 89%. AVmeanclamp:Vmean pre-clamp ratio below 0.4 detected all all patients with EEG flattening (n = 3) (accuracy 97%). The corresponding level of accuracy obtained with stump pressure was 80%. The results indicate that middle cerebral flow velocity enables an increase in the accuracy of detecting cerebral ischaemia during carotid endarterectomy.

Changes in middle cerebral artery flow velocity and pulsatility index after carotid endarterectomy

Transcranial Doppler sonography (TCD) was used in 33 patients undergoing carotid endarterectomy (CEA). Mean flow velocity (MCA MV) and the pulsatility index in the middle cerebral artery (MCA PI) were measured pre- and on six occasions postoperatively. The MCA MV was reduced by anaesthesia but was increased postoperatively (+43%, p less than 0.001) compared to the preoperative value and was still increased at late follow-up after several months. The MCA PI, which was lower preoperatively than normally reported in this age group, was not changed by anaesthesia but then rose and remained elevated, i.e. within normal limits 72 h postoperatively (+30%, p less than 0.01) as well as at late follow-up. No significant changes in MCA MV or MCA PI were noted on the contralateral side. The results from this study support earlier findings from invasive studies showing that CEA results in an increased flow in the middle cerebral artery on the operated side and an increased MCA PI suggests an increased resistance on the operated side. The findings are compatible with an increased cerebral blood flow during the first days after CEA and with the operated side supplying a greater part of the cerebral blood flow even several months after surgery.

Pre- and intraoperative transcranial Doppler: prediction and surveillance of tolerance to carotid clamping

We report 91 patients (mean age 70 years) operated upon, prospectively for a total of 100 carotid revascularizations (nine bilateral). Eighty-five of these patients had pre-, intra-, and postoperative transcranial Doppler investigations. Preoperatively, these 85 patients (92 procedures) were classified into two groups based on the results of their Doppler examinations: Group A (65 patients, 72 procedures), those who did not require an intraoperative indwelling shunt and Group B (20 patients, 20 procedures), those who did. The shunt was inserted only when the mean stump (back) pressure was less than 50 mmHg after cross-clamping. Group A all had satisfactory collaterality with a functional anterior and one or two posterior communicating arteries. Group B had no communicating arteries (anterior or posterior) identified by transcranial Doppler. In 17 of 20 patients in this group, the stump pressure was less than 50 mmHg and a shunt was placed. The overall prediction based on Doppler examination of whether or not patients would need a shunt during operation for the two groups A and B (i.e., 92 procedures) was correct in 95.6% (88/92) of cases. Moreover, six hemodynamically significant stenoses (four in the cavernous portion, two in the middle cerebral artery) were disclosed. Sensitivity and specificity of transcranial Doppler as correlated with arteriographic findings were 70 and 90%. Preoperative transcranial Doppler can measure the velocities of the principal cerebral arteries and the collateral capacity of the circle of Willis, and can forecast tolerance to carotid cross-clamping. Intraoperatively, the velocity of flow in the middle carotid artery was correlated with stump pressure, which allowed for surveillance of the shunt.