Near-infrared Spectroscopy to Indicate Selective Shunt Use During Carotid Endarterectomy

[Open surgical treatment for carotid stenoses]

BACKGROUND

Globally, stroke is considered the second most common cause of death. According to the German Federal Statistical Office, 33.6% of mortality was due to cardiovascular diseases, making them the most prevalent cause of death.

PROBLEM

Specifically, cerebral infarctions were recorded as the cause in over 16,000 cases. These figures underscore the significant role that cerebrovascular diseases play in Germany's mortality statistics. Notably, about 80% of strokes are ischemic. Moreover, one-fifth of all strokes result from extracranial carotid stenosis. The increase in stroke risk with advancing age, especially among men, is particularly striking. This trend highlights the growing importance of efficient stroke prevention and treatment in an aging society.

CONCLUSION

Open surgical therapy, as a crucial treatment method, is increasingly important, especially as an emergency intervention. Its role in modern medicine emphasizes the urgency of prioritizing this life-saving procedure in healthcare and making it widely available.

Can NIRS be a surrogate indicator of elective shunt in carotid endarterectomy? A single-center observational retrospective study says no

BACKGROUND

Neuromonitoring during carotid endarterectomy (CEA) under general anesthesia is desirable and may be useful for preventing brain ischemia, but the selection of the most appropriate method remains controversial.

PURPOSE

To determine the effectiveness of near infrared spectroscopy (NIRS) compared to multimodality intraoperative neuromonitoring (IONM) in indicating elective shunts and predicting postoperative neurological status.

METHODS

This is a retrospective observational study including 86 consecutive patients with CEA under general anesthesia. NIRS and multimodality IONM were performed during the procedure. IONM included electroencephalography (EEG), somatosensory evoked potentials (SSEPs) and transcranial motor-evoked potentials (TcMEPs). Sensitivity, specificity, and positive and negative predictive values (PPV and NPV) were calculated for each neuromonitoring modality.

RESULTS

NIRS presented a sensitivity and a specificity for detecting brain ischemia of 77.7% and 89.6%, respectively (PPV = 46.6% and NPV = 97.2%). In contrast, a 100% sensitivity and specificity for multimodality IONM was determined (PPV and NPV = 100%). No significant difference (in demographical or clinical data) between "true positive" and "false-positive" patients was identified. Among the methods included in multimodality IONM, EEG showed the best results for predicting postoperative outcome after CEA (PPV and NPV=100%).

CONCLUSION

NIRS is inferior to multimodality IONM in detecting brain ischemia and predicting postoperative neurological status during CEA under general anesthesia.

Non-Invasive Tools in Perioperative Stroke Risk Assessment for Asymptomatic Carotid Artery Stenosis with a Focus on the Circle of Willis

This review aims to explore advancements in perioperative ischemic stroke risk estimation for asymptomatic patients with significant carotid artery stenosis, focusing on Circle of Willis (CoW) morphology based on the CTA or MR diagnostic imaging in the current preoperative diagnostic algorithm. Functional transcranial Doppler (fTCD), near-infrared spectroscopy (NIRS), and optical coherence tomography angiography (OCTA) are discussed in the context of evaluating cerebrovascular reserve capacity and collateral vascular systems, particularly the CoW. These non-invasive diagnostic tools provide additional valuable insights into the cerebral perfusion status. They support biomedical modeling as the gold standard for the prediction of the potential impact of carotid artery stenosis on the hemodynamic changes of cerebral perfusion. Intraoperative risk assessment strategies, including selective shunting, are explored with a focus on CoW variations and their implications for perioperative ischemic stroke and cognitive function decline. By synthesizing these insights, this review underscores the potential of non-invasive diagnostic methods to support clinical decision making and improve asymptomatic patient outcomes by reducing the risk of perioperative ischemic neurological events and preventing further cognitive decline.

Prospective single-center study on the reliability of ipsilateral cerebral oximetry using near-infrared spectroscopy as a predictor for selective shunting during carotid endarterectomy

OBJECTIVE

Many techniques are available for the intraoperative assessment of brain perfusion during carotid endarterectomy, such as carotid stump pressure, near-infrared spectroscopy, somatosensory evoked potentials, transcranial Doppler, electroencephalography, and clinical assessment. The decision for selective carotid shunt insertion is dependent on clinical deterioration or the detection of cerebral hypoperfusion after cross-clamping of the internal carotid artery. Monitoring cerebral oximetry using near-infrared spectroscopy is a noninvasive technique for cerebral oxygen saturation measurement, reflecting changes in cerebral blood flow during carotid endarterectomy. The aim of this study was to evaluate the reliability of near-infrared spectroscopy as a predictor of selective shunting during carotid endarterectomy.

METHODS

In total, 47 conventional carotid endarterectomy surgeries were performed at our hospital between March 2016 and December 2021. All surgeries were performed under a regional cervical block supplemented with local infiltration anesthesia. All patients were monitored by cerebral oximetry using bilateral near-infrared spectroscopy probes and clinical assessment through communication with the patient (numerical, visual, and verbal) to indicate a selective shunt. Near-infrared spectroscopy values were recorded before and after internal carotid cross-clamping and after declamping. Any decrease in ipsilateral cerebral oximetry-near-infrared spectroscopy values equal to or more than 20% from the pre-clamping baseline reading associated with deterioration in neurological status (hemiparesis, aphasia, or deterioration in level of consciousness) after internal carotid artery cross-clamping was considered an indication for intraluminal carotid shunting.

RESULTS

After internal carotid artery cross-clamping, 5 of 47 patients (10.6%) developed a significant drop in cerebral oxygen saturation associated with obvious clinical assessment deterioration in verbal communication and weakness in contralateral arm power. A Pruitt-Inahara carotid shunt was subsequently inserted, and 42 patients remained stable throughout surgery. The average decline in ipsilateral near-infrared spectroscopy values was 23.8% in patients with clinical deterioration. The average decline was 8.6% in patients who remained stable.

CONCLUSIONS

Monitoring ipsilateral cerebral oximetry using near-infrared spectroscopy is an easy and reliable method for indicating selective shunting during carotid endarterectomy. A 20% decrease in ipsilateral brain tissue oximetry after internal carotid artery cross-clamping provides a reliable cut-off value for selective intraluminal carotid shunting during carotid endarterectomy.

Routine versus selective near-infrared spectroscopy-guided shunting during carotid eversion endarterectomy

OBJECTIVES

The aim of this study was to compare outcomes of routine shunting to near-infrared spectroscopy (NIRS)-guided shunting in patients undergoing eversion endarterectomy (EEA) under general anaesthesia.

METHODS

We retrospectively evaluated data of all patients undergoing EEA of the internal carotid artery (ICA) in our department from January 2011 until January 2019. Included were patients with EEA of the ICA and the patients were divided into 2 groups: selective-shunting group and routine-shunting group. Patients (i) with patch angioplasty during the surgery, (ii) undergoing surgery for restenosis and (ii) stenosis after radiation therapy, (iii) without recorded regional cerebral oxygen saturation trends, (iv) presenting with an emergency treatment indication and (v) operated upon by residents were excluded. In all patients, EEA was performed in general anaesthesia and under NIRS monitoring. One-to-one propensity score matching was used to compare EEA outcomes after routine shunting to NIRS-guided shunting. Primary end points were defined as perioperative stroke and in-hospital mortality after EEA.

RESULTS

Routine and NIRS-guided selective shunting were applied in 340 (34.0%) and 661 (66.0%) patients, respectively. A total of 277 pairs were generated via propensity score matching. Fifty-eight (20.1%) from the selective-shunting group were intraoperatively shunted. Concomitant procedures were more frequently performed in the routine-shunting group [170 (61.4%) vs 47 (17.0%), 180 (65%) vs 101 (36.5%), and 60 (21.7%) vs 6 (2.2%), P < 0.001]. The perioperative stroke rate in the routine-shunting group was higher as well [11 (4.0%) vs 3 (1.1%), P = 0.022]. In-hospital death was overall 0.2% (n = 1). Multivariable logistic regression in the matched patient indicated age (odds ratio 1.050, 95% confidence interval 1.002-1.104, P = 0.046) and routine shunting (odds ratio 2.788, confidence interval 1.119-7.428, P = 0.032) as risk factors for perioperative stroke during EEA of the ICA.

CONCLUSIONS

We found that, during EEA of the ICA, under general anaesthesia, NIRS-guided selective shunting was associated with a lower incidence of perioperative stroke than routine shunting.

Cerebral oximetry monitoring by means of INVOS-4100 as a predictor of ischemic events during carotid endarterectomy

Background

Several methods have been proposed to monitor cerebral perfusion during carotid endarterectomy (CEA), with the purpose of minimizing the risk of perioperative stroke. The INVOS-4100 is able to detect cerebral oxygen saturation providing an intraoperative real-time monitoring system of cerebral oximetry. The aim of this study was to evaluate the performance of the INVOS-4100 in predicting cerebral ischemia during CEA.

Methods

Between January 2020 and May 2022, 68 consecutive patients were scheduled for CEA either under general anesthesia or regional anesthesia with deep and superficial cervical block. Vascular oxygen saturation was recorded continually through INVOS before and during clamping of the ICA. Awake testing was performed in the group of patients undergoing CEA under regional anesthesia.

Results

Sixty-eight patients were included; 43 were males (63.2%). Severe stenosis of the artery was present in 92%. Forty-one (60.3%) patients were monitored by INVOS, while 22 (39.7%) underwent awake testing. Mean clamping time was 20 ± 6.6 min. Patients undergoing awake testing had a lower hospital stay and ICU stay during admission (p = 0.011 and p = 0.007 respectively). Comorbidities correlated with a higher ICU stay (p < 0.05). The INVOS monitoring was able to predict ischemic events with a sensitivity of 98% (AUC = 0.976).

Conclusions

The present study demonstrates that cerebral oximetry monitoring was a strong predictor of cerebral ischemia, although it was not possible to determine the non-inferiority of cerebral oximetry compared to awake testing. Nonetheless, the use of cerebral oximetry evaluates only perfusion in the superficial brain tissue and an absolute rSO2 value corresponding to significant cerebral ischemia has not been established. Therefore, larger prospective studies that correlate cerebral oximetry with neurologic outcomes are needed.

Effect of combined use of cerebral oximetry and electroencephalogram monitoring on the incidence of perioperative neurocognitive disorders in adult cardiac and non-cardiac surgery: A systematic review of randomized and non-randomized trials

Background: There is insufficient evidence to recommend using either intraoperative cerebral oximetry or (processed) electroencephalogram (EEG) alone for preventing perioperative neurocognitive disorders (PNDs). Objective: To evaluate the effectiveness of combined use of cerebral oximetry and electroencephalogram-guided anesthesia on the incidence of PNDs in adult patients undergoing cardiac and non-cardiac interventions. Methods: A PICOS - based systematic review of English articles using Pubmed and Embase (from inception to August 2022) was performed. There were no exclusion criteria regarding the type of the study. Abstract proceedings and new study protocols or ongoing studies were not included. Review articles were analyzed in search of eligible references. All possible terms that were illustrative of PNDs were used. Results: Among the 63 full manuscripts that were analyzed in detail, 15 met the inclusion criteria. We found 2 retrospective, 8 prospective observational and 5 randomized controlled trials of which 1 did not evaluate the use of neuromonitoring in the randomization process. The definition and the methods used to diagnose PNDs were very heterogeneous. Only 8 studies used an algorithm to avoid/treat cerebral oxygen desaturation and/or to treat EEG abnormalities. Overall, there was a tendency towards less PNDs in studies where such an algorithm was used. Conclusions: Our results suggest that integrating information obtained from cerebral oximetry and an EEG monitor may reduce the incidence of PNDs whenever an adapted algorithm is used to improve brain function.

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.

Outcomes and role of shunting during carotid endarterectomy for symptomatic patients

OBJECTIVE

Shunt placement during carotid endarterectomy (CEA) is often advocated to protect the ischemic penumbra in patients with symptomatic carotid stenosis. This study assesses the effect of shunt placement on postoperative stroke risk in symptomatic patients undergoing CEA.

METHODS

We queried the American College of Surgeons National Surgical Quality Improvement Program database (2016-2019) for CEA cases with complete CEA procedure-targeted data. Symptomatic patients were identified as having a preoperative diagnosis of stroke on presentation (DS), transient ischemic attack (TIA), amaurosis fugax (AF), or temporary monocular blindness (TMB). DS patients were further analyzed according to the severity of their stroke based on their modified Rankin Scale (mRS). To better assess the effect of shunt placement on stroke rate, we compared cases of CEA with patch angioplasty technique, with and without the use of intraoperative shunt. Patients who underwent carotid eversion or primary closure were excluded. Baseline demographics and perioperative outcomes were compared using Chi-square and Mann-Whitney U test. Multivariate analysis was performed to identify independent risk factors for postoperative stroke and cranial nerve injury.

RESULTS

We identified 4,652 cases of CEA with patch angioplasty in symptomatic patients, including 1,889 (40.6%) with shunt placement and 2,763 (59.4%) without. Age, race, and sex distributions were similar for both procedures. Compared to patients without shunt, those with shunt had significantly higher rates of emergency (9.1% vs 7.0%, P = .010) and non-elective surgery (40.3% vs 37.2%, P = .035), general anesthesia (97.0% vs 86.3%, P < .001), and bleeding disorders (27.2% vs 22.7%, P < .001). Thirty-day incidence of postoperative stroke was similar between patients who had shunt placement (3.2%) and those who did not (2.6%) (P = .219). Additionally, subgroup analysis failed to show any benefit of shunting on postoperative stroke regardless of preoperative symptoms or neurologic disability. In contrast, shunt placement was associated with increased rate of cranial nerve injury (4.1% vs 2.4%, P = .001). Multivariate analysis revealed that non-elective surgery (OR 1.99, 95% CI 1.36-2.91, P < .001) and DS (vs TIA/AF/TMB) (OR 1.64, 95% CI 1.12-2.41, P = .012) were predictive of 30-day postoperative stroke. After adjusting for confounders, shunt placement had no effect on stroke risk at 30 days but remained an independent risk factor for cranial nerve injury (aOR 1.87, 95% CI 1.32-2.64, P < .001).

CONCLUSIONS

In symptomatic patients undergoing CEA with patch angioplasty, shunting is associated with increased risk of cranial nerve injury without reduction in postoperative stroke risk.

Near Infrared Spectroscopy For Cerebral Hemodynamic Monitoring During Carotid Endarterectomy Under General Anesthesia

Background:

Near infrared spectroscopy (NIRS) is a noninvasive method for continuous monitoring of cerebral oxygenation.

Objective:

To describe the intraoperative behavior of NIRS variables used to evaluate hemodynamic response in patients with atherosclerotic disease undergoing carotid endarterectomy under general anesthesia.

Methods:

Fifteen volunteers with atherosclerotic carotid disease with indications for endarterectomy were evaluated. After selection of patients, carotid stenosis was confirmed by appropriate diagnostic methods. NIRS was used for intraoperative monitoring. The variables total hemoglobin (Hb), oxygenated hemoglobin (O2Hb), deoxygenated hemoglobin (HHb), and regional oxygen saturation (rSO2) were evaluated at three intraoperative time points: before, during, and after carotid clamping.

Results and Discussion:

Measurements recorded by NIRS showed that, during the first 5 min of clamp time, patients experienced a decline in O2Hb levels, an increase in HHb levels, and a marked decrease in rSO2. Hb remained constant throughout the procedure. At the post-clamping time point, HHb, O2Hb, and rSO2 returned to patterns similar to those observed before clamping.

Conclusion:

NIRS was able to reliably and accurately identify the three stages of carotid endarterectomy and may predict the risk of cerebral hypoxia during carotid clamping under general anesthesia.

Hybrid Repair with Reversed Sequence Supra-aortic Debranching in Ruptured Arch Aneurysm

Aortic arch pathology in a high-risk patient in whom the resternotomy approach is unfeasible due to treated mediastinitis after ascending aortic replacement presents a unique challenge for hybrid arch repair (HAR) because of the need for supra-aortic debranching from unusual inflow sites other than the ascending aorta. This report describes a "reversed sequence" extra-anatomical supra-aortic debranching procedure as a salvage technique performed to enable HAR. An 83-year-old woman with a history of ascending aortic replacement for type A aortic dissection, mediastinitis complicated by sternal osteomyelitis, and a chest wall reconstructed with a rectus abdominis myocutaneous flap presented with chest pain because of a contained dissecting arch aneurysm rupture. The patient underwent supra-aortic debranching from the bilateral common femoral arteries and thoracic endovascular aortic repair to the ascending aorta under cerebral near-infrared spectroscopy (NIRS) monitoring. Completion imaging by angiography demonstrated successful exclusion of the ruptured aneurysm. The regional cerebral oxygen saturation level, monitored by NIRS, did not change markedly during surgery. The patient was neurologically intact with adequate cerebral blood flow assessed postoperatively by ¹²³ I-IMP single photon emission computed tomography. Total debranching of the supra-aortic vessels from the common femoral artery for inflow is feasible and provides adequate cerebral perfusion. This procedure may offer an alternative treatment option in patients with complex conditions involving aortic arch pathology.

Carotid Endarterectomy

Stroke is the second leading cause of death worldwide. One of the main causes of stroke is carotid artery stenosis. Stenosis with atherosclerosis in the carotid artery can cause stroke by hemodynamic ischemia or artery to artery embolism. A most common surgical intervention for carotid artery stenosis is carotid endarterectomy (CEA). Many studies on CEA have been reported and suggested medical indications. For symptomatic carotid stenosis, generally, CEA may be indicated for patients with more than 50% stenosis and is especially beneficial in men, patients aged 75 years or older, and patients who underwent surgery within 2 weeks of their last symptoms. For asymptomatic carotid stenosis, CEA may be indicated for those with more than 60% stenosis, though each guideline has different suggestions in detail. In order to evaluate the indication for CEA in each case, it is important to assess risks for CEA carefully including anatomical factors and comorbidities, and to elaborate each strategy for each operation based on preoperative imaging studies including carotid ultrasonography, magnetic resonance imaging and angiography. In surgery there are many tips on operative position, procedure, shunt usage and monitoring to perform a safe and smooth operation. Now that carotid artery stenting has been rapidly developed, better understanding for CEA is required to treat carotid artery stenosis adequately. This chapter must be a good help to understand CEA well.

Clamped Carotid Dissection Can Reduce Postoperative Stroke After Carotid Endarterectomy

Background: The outcomes of carotid endarterectomy (CEA) are constantly reported in a multitude of studies; however, the specific causes of perioperative stroke have been scarcely investigated. The aim of the present study was to analyze and categorize the causes of perioperative strokes after CEA. Methods: All CEAs performed from 2006 to 2019 in a single center were collected. CEA was routinely performed under general anesthesia, with routine shunting and patching, using cerebral near-infrared spectroscopy monitoring. Carotid exposure technique was classified as either clamped-dissection (CD) or preclamping-dissection (PCD) if the carotid bifurcation was dissected after or prior to carotid clamping. Perioperative and 30-day strokes and their possible mechanisms were evaluated according to preoperative symptoms and surgical technique adopted. Results: Among 1760 CEAs performed, 30 (1.7%) perioperative strokes occurred. 14 (47%) were identified upon emergence from general anesthesia, and 16 (53%) were noted in the first 30 days following intervention. Stroke etiology was categorized as follows: technical (acute thrombosis or intimal flap or due to intraoperative complications), embolic (no recognized technical defect), hemorrhagic, or contralateral. Symptomatic patients had a significantly higher rate of any type of stroke than asymptomatic patients (3.8% vs 0.9%, P = .0001). CD was protective for postoperative stroke (0.9% vs 3.1%, P = .001) in both symptomatic and asymptomatic patients (2.5% vs 5.9%, P = .05; 0.4% vs 1.9%, P = .005), particularly for the cohort in which symptomatic patients (0.7% vs 3.2%, P = .04) suffered postoperative embolic stroke. Conclusion: Perioperative stroke in CEA may be multifactorial in etiology, including a result of technical errors. A CD technique may help reduce the incidence of perioperative stroke.

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.

Variation in perioperative cerebral and hemodynamic monitoring during carotid endarterectomy

BACKGROUND

Hemodynamic disturbances cause half of the perioperative strokes following carotid endarterectomy (CEA). Guidelines strongly recommend strict pre- and postoperative blood pressure (BP) monitoring in CEA patients, but do not provide firm practical recommendations. Although in the Netherlands 50 centres perform CEA, no national protocol on perioperative hemodynamic, and cerebral monitoring exists. To assess current monitoring policies of all Dutch CEA-centres, a national survey was conducted.

METHODS

Between May and July 2017 all 50 Dutch CEA-centres were invited to complete a 42-question survey addressing perioperative hemodynamic and cerebral monitoring during CEA. Nonresponders received a reminder after 1 and 2 months. By November 2017 the survey was completed by all centres.

RESULTS

Preoperative baseline BP was based on a single bilateral BP-measurement at the outpatient-clinic in the majority of centres (n = 28). In 43 centres (86%) pre-operative monitoring (transcranial Doppler (TCD, n = 6), electroencephalography (EEG, n = 11), or TCD + EEG (n = 26)) was performed as a baseline reference. Intraoperatively, large diversity for type of anaesthesia (general: 45 vs. local [LA]:5) and target systolic BP (>100 mm hg - 160 mm hg [n = 12], based on preoperative outpatient-clinic or admission BP [n = 18], other [n = 20]) was reported. Intraoperative cerebral monitoring included EEG + TCD (n = 28), EEG alone (n = 13), clinical neurological examination with LA (n = 5), near-infrared spectroscopy with stump pressure (n = 1), and none due to standard shunting (n = 3). Postoperatively, significant variation was reported in standard duration of admission at a recovery or high-care unit (range 3-48 hr, mean:12 hr), maximum accepted systolic BP (range >100 mm hg - 180 mm Hg [n = 32]), postoperative cerebral monitoring (standard TCD [n = 16], TCD on indication [n = 5] or none [n = 24]) and in timing of postoperative cerebral monitoring (range directly postoperative - 24 hr postoperative; median 3 hr).

CONCLUSIONS

In Dutch centres performing CEA the perioperative hemodynamic and cerebral monitoring policies are widely diverse. Diverse policies may theoretically lead to over- or under treatment. The results of this national audit may serve as the baseline dataset for development of a standardized and detailed (inter)national protocol on perioperative hemodynamic and cerebral monitoring during CEA.

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 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.

Near-Infrared Spectroscopy (NIRS) for Cerebral and Tissue Oximetry: Analysis of Evolving Applications

THE USE OF NEAR-INFRARED SPECTROSCOPY (NIRS) has increased significantly worldwide in the past decade. This technology, first described more than 40 years ago, is based on the fact that near-infrared light is able to penetrate biologic tissue and can obtain real-time, noninvasive information on tissue oxygenation and metabolism. In the clinical setting, NIRS has been able to provide clinicians potentially valuable information in patients with impaired microcirculations (systemic and cerebral). Near-infrared spectroscopy has progressed beyond assessment of brain oxygenation to monitor local tissue and muscle oxygenation and perfusion. This review analyzes the published data and provides the clinician a comprehensive account of the perioperative utility of NIRS in cardiac, vascular and thoracic surgery, as well as its increasing role in tissue/muscle oxygenation monitoring.

The Anatomy of the Circle of Willis Is Not a Strong Enough Predictive Factor for the Prognosis of Cross-Clamping Intolerance during Carotid Endarterectomy

Carotid endarterectomy (CEA) is safe and effective in reducing the risk of stroke in symptomatic severe carotid artery stenosis. Having information about cross-clamping (CC) intolerance before surgery may reduce the complication rate. The purpose of this study was to assess the usefulness of magnetic resonance angiography (MRA) and magnetic resonance angiography perfusion (P-MR) in determining the risk of CC intolerance during CEA. Material and methods: 40 patients after CEA with CC intolerance were included in Group I, and 15 with CC tolerance in Group II. All patients underwent MRA of the circle of Willis (CoW), P-MR with or without Acetazolamide; P(A)-MR in the postoperative period. Results: CoW was normal in the MRA in three cases (7.5%) in Group I, and in eight (53%) in Group II. We found P-MR abnormalities in all patients from Group I and in 40% from Group II. Using a calculated cut-off point of 0.322, the patients were classified as CC tolerant with 100% sensitivity or as CC intolerant with 95% specificity. After evaluating P-MR or MRA alone, the percentage of false negative results significantly increased. Conclusion: The highest value in predicting cross-clamping intolerance is achieved by using analysis of P(A)-MR and MRA of the CoW in combination.

[Near-infrared spectroscopy : Technique, development, current use and perspectives]

Near-infrared spectroscopy (NIRS) has been available in research and clinical practice for more than four decades. Recently, there have been numerous publications and substantial developments in the field. This article describes the clinical application of NIRS in relation to current guidelines, with a focus on pediatric and cardiac anesthesia. It discusses technical and physiological principles, pitfalls in clinical use and presents (patho)physiological influencing factors and derived variables, such as fractional oxygen extraction (FOE) and the cerebral oxygen index (COx). Recommendations for the interpretation of NIRS values in connection with influencing factors, such as oxygen transport capacity, gas exchange and circulation as well as an algorithm for cardiac anesthesia are presented. Limitations of the method and the lack of comparability of values from different devices as well as generally accepted standard values are explained. Technical differences and advantages compared to pulse oxymetry and transcranial Doppler sonography are illuminated. Finally, the prognostic significance and requirements for future clinical studies are discussed.

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.

Ocular blood flow by laser speckle flowgraphy to detect cerebral ischemia during carotid endarterectomy

Laser speckle flowgraphy (LSFG) is a noninvasive technique that can measure relative blood flow velocity in the optic fundus contributed by the ophthalmic artery, the main first branch originating from the internal carotid artery (ICA). The aim of this study was to assess the feasibility of ocular blood flow measurement by LSFG to detect ischemic stress due to carotid clamping during carotid endarterectomy (CEA). Nineteen patients undergoing CEA with ocular blood flow measurement by LSFG and intraoperative monitoring (IOM) were prospectively enrolled between August 2016 and March 2019. The mean blur rate (MBR) of ocular blood flow by LSFG, representing relative blood flow of the branch of the retinal artery originating from the optic nerve head, was compared between before and after carotid clamping during CEA. The correlation between the reduction ratio of MBR and the regional saturation oxygen (rSO₂) index by near infrared spectroscopy was investigated. Ocular blood flow measurement by LSFG could not be performed in one patient with a severe cataract. In the other 18 patients, LSFG could be performed in all 106 sessions during surgery. The MBR reduction ratio between before and after carotid clamping ranged from - 12 to 100%. The MBR reduction ratio was positively correlated with the rSO₂ index (r = 0.694, 95% confidence interval: 0.336-0.877, p = 0.001). The MBR reduction ratio of ocular blood flow by LSFG after carotid clamping was significantly correlated with the rSO₂ index. The ocular blood flow by LSFG could be considered an adjunct modality for evaluating cerebral ischemic tolerance during CEA.

Near-infrared spectroscopy as a predictor of cerebral ischaemia during carotid endarterectomy in awake patients

Objectives

The aim of our study was to evaluate the near-infrared spectroscopy monitoring system to detect cerebral ischaemia, find indications for selective shunting during carotid endarterectomy and compare it with an internal carotid artery stump pressure monitoring technique in patients operated under local anaesthesia.

Methods

During January 2015 and November 2018, 131 patients undergoing carotid endarterectomy under local anaesthesia were prospectively included in the study. Near-infrared spectroscopy as intraoperative monitoring was applied and compared with stump pressure.

Results

Carotid endarterectomy was performed successfully in 106 patients operated under local anaesthesia. Meanwhile, 25 patients developed neurological changes (motor or consciousness impairment, weakness of extremities, cognitive decline) during clamping, and all of them received a shunt. ΔrSO2, stump pressure and rSO2 (–11 ± 8%, 31 ± 6mmHg, 58 ± 11) values were smaller in the group of shunted subjects versus non-shunted group subjects (–2 ± 5%, 61 ± 17 mmHg, 64 ± 8) after 1 min of internal carotid artery clamping ( p < 0.05). Statistical analysis showed a sensitivity of 90% (95% CI: 0.85–0.95) and a specificity of 70% (95% CI: 0.62–0.78) for a ≥10% drop in ΔrSO2 to predict ischaemia symptoms during carotid clamping. Using stump pressure with a cut-off value of ≤40 mmHg for predicting symptoms, the sensitivity was 82% and specificity 54%.

Conclusions

Near-infrared spectroscopy is a suitable non-invasive cerebral oxygenation monitoring method during carotid endarterectomy. A 10% decrease of ΔrSO2 had a good correlation with clinical cerebral ischaemia signs and matched well with the stump pressure cut-off value of ≤40 mmHg. There is a possibility of near-infrared spectroscopy to replace stump pressure in cerebral oxygenation monitoring during carotid endarterectomy. However, we need larger prospective multicentre studies to identify the optimal threshold for shunt requirement.

Effects of remote ischemic preconditioning on regional cerebral oxygen saturation in patients in the beach chair position during shoulder surgery: A double-blind randomized controlled trial

STUDY OBJECTIVE

The beach chair position for shoulder surgery induces cerebral hypoperfusion. We evaluated the effects of remote ischemic preconditioning (RIPC) prior to surgery to ameliorate cerebral desaturation in a double-blind randomized fashion.

DESIGN

Blinded, prospective, randomized study.

SETTING

Operating room & postoperative recovery room, tertiary university hospital.

PATIENTS

Seventy patients scheduled for shoulder surgery were recruited. After excluding 7 patients according to the exclusion criteria, 63 patients were randomized into two groups (control and RIPC).

INTERVENTIONS

Remote ischemic preconditioning was applied by briefly inflating a tourniquet on the thigh three times just after inducing anesthesia in the RIPC group.

MEASUREMENTS

The changes in regional cerebral oxygen saturation, hemodynamic values, laboratory values, and serum levels of cytokines including interleukin (IL)-1β, IL-6, IL-10 and transforming growth factor-β were measured.

MAIN RESULTS

The remote ischemic preconditioning group had higher regional cerebral oxygen saturation just after establishment of the beach chair position (P = 0.002) and lower cerebral desaturation (P = 0.007) during operation than the control group. Hemodynamic and laboratory values did not differ between the groups. There were no significant intergroup differences in cytokine levels.

CONCLUSION

Remote ischemic preconditioning before surgery ameliorates cerebral desaturation in patients in the beach chair position during shoulder surgery. Trial Registry Number: KCT0001384 (http://cris.nih.go.kr).

Comparison of the effect of sevoflurane or propofol anesthesia on the regional cerebral oxygen saturation in patients undergoing carotid endarterectomy: a prospective, randomized controlled study

Background

The monitoring of regional cerebral oxygen saturation (SrO₂) using near-infrared spectroscopy is useful method to detect cerebral ischemia during. Sevoflurane and propofol decrease cerebral metabolic rate (CMRO₂) in a similar manner, but the effects on the cerebral blood flow (CBF) are different. We hypothesized that the effects of sevoflurane and propofol on SrO₂ were different in patients with deficits of CBF. This study compared the effect of sevoflurane and propofol on SrO₂ of patients undergoing cerebral endarterectomy (CEA).

Method

Patients undergoing CEA were randomly assigned to the sevoflurane or propofol group (n = 74). The experiment was preceded in 2 stages based on carotid artery clamping. The first stage was from induction of anaesthesia to immediately before clamping of the carotid artery, and the second stage was until the end of the operation after clamping of the carotid artery. Oxygen saturation (SrO₂, SpO₂), haemodynamic variables (blood pressure, heart rate), respiratory parameters (end-tidal carbon dioxide tension, inspired oxygen tension), concentration of anesthetics, and anesthesia depth (bispectral index score) were recorded.

Results

During stage 1 period (before carotid artery clamping), the mean value of the relative changes in SrO₂ was higher (P = 0.033) and the maximal decrease in SrO₂ was lower in the sevoflurane group compared with the propofol group (P = 0.019) in the contralateral (normal) site. However, there is no difference in ipsilateral site (affected site). SrO₂ decreased after carotid artery clamping and increased after declamping, but the difference was not significant between two groups. Changes in mean arterial blood pressure was lower in sevoflurane group than propofol group after the carotid artery declamping (P = 0.048).

Conclusion

Propofol-remifentanil anesthesia was comparable with sevoflurane-remifentanil anesthesia in an aspect of preserving the SrO₂ in patients undergoing carotid endarterectomy.

Trial registration

Clinical Trials.gov identifier: NCT02609087, retrospectively registered on November 18, 2015.

The effect of cerebral oximeter use on the shunt placement concerning carotid endarterectomy surgery

Background:

During carotid arterial endarterectomy (CAE) surgery, an intraluminal shunt is used to prevent hypoperfusion, which can be caused by a cross-clamping cerebral ischemia. However, routine shunt use is not recommended. Various cerebral monitoring techniques are used to determine the need for shunt placement. In this study, retrospective analysis of data on the efficacy of cerebral oximetry in the decision of shunt use during elective CAE surveys was planned.

Materials and Methods:

We collected data on 68 patients operated under general anesthesia between December 2016 and December 2017. Patients were evaluated for near infrared spectrometry (NIRS) and stump pressure values and whether shunt was placed or not.

Results:

Eight (11.7%) patients were shunting. NIRS value after cross-clamping was lower in patients with shunt. Stump pressure values were below 40 mmHg.

Conclusions:

Cerebral monitoring in elective CAE operations has great importance in determining the necessity of using intraluminal shunt to reduce the complications that may occur.

Real-world experience of extracranial carotid artery interventions for atherosclerotic disease during a 10-year period

BACKGROUND

The aim of this study was to assess the long-term outcome of carotid disease treatment with endarterectomy or stenting (CEA or CAS) in a real-world setting during a 10-year period.

METHODS

A single center retrospective study with prospectively collected data including patients (symptomatic or asymptomatic) being treated with CEA or CAS. Survival, restenosis, stroke and major adverse cardiac events (MACE) were the outcomes.

RESULTS

A total of 413 patients (mean age of 69±3.5 years; 80%, 333/413 males) were treated with CEA (83.7%, 346/413) or CAS (16.3%, 67/413). Most of the patients were asymptomatic (60%, 248/413). The incidence of in-hospital stroke and death was 0.5% (2/413) and 0.7% (3/413), respectively. The survival rate at 1, 3 and 5 years was 98%, 94.7% and 90.6%, respectively. The freedom of re-stenosis at 1, 3 and 5 years was 99%, 98% and 90.5%, respectively. The freedom of any stroke at 1, 3 and 5 years was 99%, 97% and 94.8%, respectively. The freedom of MACE at 1, 3 and 5 years was 97.6%, 91.5% and 86.3%, respectively. Symptomatic presentation was associated with higher rates of restenosis after CEA and higher rate of mortality (P=0.025) and MACE (P=0.022) after CAS.

CONCLUSIONS

Carotid interventions remain durable treatment methods of carotid disease. Long-term outcomes regarding mortality, restenosis, and risk of stroke or MACE are similar between CAS and CEA for asymptomatic patients. Symptomatic presentation may be associated with higher rates of restenosis after CEA and higher rate of mortality and MACE after CAS, however larger studies are needed to clarify this issue.

Near-Infrared Spectroscopy versus Transcranial Doppler-Based Monitoring in Carotid Endarterectomy

Background

Proper monitoring of cerebral perfusion during carotid artery surgery is crucial for determining if a shunt is needed. We compared the safety and reliability of near-infrared spectroscopy (NIRS) with transcranial Doppler (TCD) for cerebral monitoring.

Methods

This single-center, retrospective review was conducted on patients who underwent carotid endarterectomy (CEA) using selective shunt-based TCD or NIRS at Daegu Catholic University Medical Center from November 2009 to June 2016. Postoperative complications were the primary outcome, and the distribution of risk factors between the 2 groups was compared.

Results

The medical records of 74 patients (45 TCD, 29 NIRS) were reviewed. The demographic characteristics were similar between the 2 groups. One TCD patient died within the 30-day postoperative period. Postoperative stroke (n=4, p=0.15) and neurologic complications (n=10, p=0.005) were only reported in the TCD group. Shunt usage was 44.4% and 10.3% in the TCD and NIRS groups, respectively (p=0.002).

Conclusion

NIRS-based selective shunting during CEA seems to be safe and reliable for monitoring cerebral perfusion in terms of postoperative stroke and neurologic symptoms. It also reduces unnecessary shunt usage.

Simultaneous functional near-infrared spectroscopy and electroencephalography for monitoring of human brain activity and oxygenation: a review

Multimodal monitoring has become particularly common in the study of human brain function. In this context, combined, synchronous measurements of functional near-infrared spectroscopy (fNIRS) and electroencephalography (EEG) are getting increased interest. Because of the absence of electro-optical interference, it is quite simple to integrate these two noninvasive recording procedures of brain activity. fNIRS and EEG are both scalp-located procedures. fNIRS estimates brain hemodynamic fluctuations relying on spectroscopic measurements, whereas EEG captures the macroscopic temporal dynamics of brain electrical activity through passive voltages evaluations. The "orthogonal" neurophysiological information provided by the two technologies and the increasing interest in the neurovascular coupling phenomenon further encourage their integration. This review provides, together with an introduction regarding the principles and future directions of the two technologies, an evaluation of major clinical and nonclinical applications of this flexible, low-cost combination of neuroimaging modalities. fNIRS-EEG systems exploit the ability of the two technologies to be conducted in an environment or experimental setting and/or on subjects that are generally not suited for other neuroimaging modalities, such as functional magnetic resonance imaging, positron emission tomography, and magnetoencephalography. fNIRS-EEG brain monitoring settles itself as a useful multimodal tool for brain electrical and hemodynamic activity investigation.

Brain Oxygen Supply Parameters in the Risk Assessment of Cerebral Complications During Carotid Endarterectomy

OBJECTIVE

To determine whether preoperative regional cerebral oxygen saturation (rSO₂) and the decrease in rSO₂ during carotid clamping were predictive of the risk for neurologic complications in carotid endarterectomy and to determine the cutoff values of the studied parameters.

DESIGN

Cohort, prospective, nonrandomized trial.

SETTING

Research Institute of Circulation Pathology, Novosibirsk, Russia.

PARTICIPANTS

The study comprised 466 adults who underwent carotid endarterectomy since 2012.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Patient characteristics, postoperative complications, and brain oxygen supply during carotid endarterectomy were analyzed. The primary endpoints were the perioperative and early postoperative neurologic complications. Ischemic stroke was diagnosed in 1.5% of patients, and cognitive disorders were reported in 2.6% of patients. Preoperative rSO₂ of 50% was the cutoff value for the prediction of stroke outcome after carotid endarterectomy, with a sensitivity of 90.7% and specificity of 66.7%. A 20% decrease in rSO₂ during temporary carotid clamping was the cutoff value for the prediction of stroke, with a sensitivity of 86.0% and specificity of 57.1%, and for the prediction of cognitive disorders, with a sensitivity of 88.1% and specificity of 58.3%. Preoperative rSO₂ less than 50% and a decrease in rSO₂ of at least 20% during temporary carotid artery clamping caused a significant increase in the hospitalization period.

CONCLUSIONS

A 20% or more decrease in rSO₂ during temporary internal carotid artery clamping during carotid endarterectomy caused a 10-fold increased risk of ischemic stroke and an 8-fold increased risk of cognitive disorders, whereas preoperative rSO₂ less than 50% resulted in a 6-fold increased risk of ischemic stroke in the perioperative and early postoperative periods of carotid endarterectomy.

Effects of intravenously administered indocyanine green on near-infrared cerebral oximetry and pulse oximetry readings

Background

Intravenously administered indocyanine green (ICG) may cause misreadings of cerebral oximetry and pulse oximetry in patients undergoing carotid endarterectomy under general anesthesia. The present study determined the effects of two different doses (12.5 mg vs. 25 mg) of ICG on regional cerebral tissue oxygen saturation (SctO₂) and percutaneous peripheral oxygen saturation (SpO₂).

Methods

Twenty-six patients receiving ICG for videoangiography were divided into two groups according to the dosage (12.5 mg and 25 mg, n = 13 in each group). Heart rate, arterial blood pressure, SctO₂, and SpO₂ were measured before and after an intravenous bolus administration of ICG.

Results

Following the dye administration, no changes in heart rate or arterial blood pressure were noted in either group. SctO₂ was increased in both groups; however, the magnitude of the increase was greater (21.6 ± 5.8% vs. 12.6 ± 4.1%, P < 0.0001) and more prolonged (28.4 ± 9.6 min vs. 13.8 ± 5.2 min, P < 0.0001) in the 25 mg group than in the 12.5 mg group. In contrast, SpO₂ was decreased in both groups; the magnitude of the decrease was greater in the 25 mg group than in the 12.5 mg group (4.0 ± 0.8% vs. 1.6 ± 1.0%, P < 0.0001). There were no differences in the time to reach the peak SctO₂ or to reach the nadir SpO₂ between the two groups.

Conclusions

In patients given ICG for videoangiography, a 25 mg bolus results in a greater and more prolonged increase in SctO₂ and a greater reduction in SpO₂ than a 12.5 mg bolus, with no differences in the time to reach the peak SctO₂ or to reach the nadir SpO₂.

Cerebral oxygenation and processed EEG response to clamping and shunting during carotid endarterectomy under general anesthesia

Clamping and shunting during carotid endarterectomy (CEA) surgery causes changes in cerebral blood flow. The purpose of this study was to assess and compare, side by side, the cerebral oxygenation (rSO2) and processed electroencephalogram (EEG) response bilaterally to carotid artery clamping and shunting in patients undergoing CEA under general anesthesia. With institutional approval and written informed consent, patients undergoing CEA under general anesthesia and routine carotid artery shunting were recorded bilaterally, simultaneously and continuously with an rSO2 and processed EEG monitor. The response of the monitors during carotid artery clamping and shunting were assessed and compared between monitors and bilaterally within each monitor. Sixty-nine patients were included in the study. At clamping the surgical-side and contralateral-side rSO2 dropped significantly below the baseline incision value (-17.6 and -9.4% respectively). After shunting, the contralateral-side rSO2 returned to baseline while the surgical-side rSO2 remained significantly below baseline (-9.0%) until the shunt was removed following surgery. At clamping the surgical-side and contralateral-side processed EEG also dropped below baseline (-19.9 and -20.6% respectively). However, following shunt activation, the processed EEG returned bilaterally to baseline. During the course of this research, we found the rSO2 monitor to be clinically more robust (4.4% failure rate) than the processed EEG monitor (20.0% failure rate). There was no correlation between the rSO2 or processed EEG changes that occurred immediately after clamping and the degree of surgical side stenosis measured pre-operatively. Both rSO2 and processed EEG respond to clamping and shunting during CEA. Cerebral oximetry discriminates between the surgical and contralateral side during surgery. The rSO2 monitor is more reliable in the real-world clinical setting. Future studies should focus on developing algorithms based on these monitors that can predict clamping-induced cerebral ischemia during CEA in order to decide whether carotid artery shunting is worth the associated risks. From the practical point of view, the rSO2 monitor may be the better monitor for this purpose.

Cerebral oxygenation using near-infrared spectroscopy in the beach-chair position during shoulder arthroscopy under general anesthesia

PURPOSE

To examine the risks of shoulder arthroscopy in the beach-chair position (BCP) as opposed to the lateral decubitus position. The challenge during general anesthesia, particularly with the patient in the BCP, has been to ascertain the lower limit of blood pressure autoregulation, correctly measure mean arterial pressure, and adequately adjust parameters to maintain cerebral perfusion. There is increasing concern about the BCP and its association with intraoperative cerebral desaturation events (CDEs). Assessment of CDEs intraoperatively remains difficult; the emerging technology near-infrared spectroscopy (NIRS) may provide noninvasive, inexpensive, and continuous assessment of cerebral perfusion, offering an "early warning" system before irreversible cerebral ischemia occurs.

METHODS

A systematic review was undertaken to determine the incidence of intraoperative CDEs as measured by NIRS and whether it is possible to risk stratify patients for intraoperative CDEs, specifically the degree of elevation in the BCP.

RESULTS

Searching Medline, Embase, and the Cochrane Central Register of Controlled Trials from inception until December 30, 2013, we found 9 studies (N = 339) that met our search criteria. The Level of Evidence was III or IV.

CONCLUSIONS

There remains a paucity of high-level data. The mean incidence of CDEs was 28.8%. We found a strong positive correlation between CDEs and degree of elevation in the BCP (P = .056). Emerging evidence (Level IV) suggests that we may be able to stratify patients on the basis of age, history of hypertension and stroke, body mass index, diabetes mellitus, obstructive sleep apnea, and height. The challenge remains, however, in defining the degree and duration of cerebral desaturation, as measured by NIRS, required to produce measureable neurocognitive decline postoperatively.

LEVEL OF EVIDENCE

Level IV, systematic review of Level III and IV studies.

Intraoperative management of carotid endarterectomy

First reports on surgical treatment of cerebrovascular atherosclerosis date to the early 1950s. With advancements in surgical technique, carotid endarterectomy (CEA) has become the treatment of choice for patients with both symptomatic and asymptomatic severe carotid stenosis. Given the benefits that surgery offers beyond medical management, the number of CEA procedures continues to increase. The intraoperative management of patients undergoing CEA is challenging because of the combination of patient and surgical factors. This article explores and reviews the literature on anesthetic management and considerations of patients undergoing CEA.