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.

Near-infrared spectroscopy cerebral oximetry as a predictor of neurological intolerance during carotid artery stenting with proximal protection

Carotid artery stenting (CAS) with proximal protection can expose occlusion intolerance (OI) due to ipsilateral cerebral hemisphere hypoperfusion. Near-infrared spectroscopy (NIRS) cerebral oximetry can monitor regional cerebral oxygenation (rSO₂) in the frontal lobes, and is used during CAS to predict cerebral blood flow insufficiency. The aim of this study was to evaluate rSO₂ as a predictor of OI during CAS. We retrospectively examined 146 patients who underwent CAS with proximal protection. An INVOS® NIRS oximeter was used for rSO₂ measurement, which was compared with stump pressure (SP) measured by a guiding catheter during occlusion of the common carotid artery (CCA) and external carotid artery. For the lesion with OI, distal filter protection was combined with proximal protection if possible, and CCA was intermittently occluded during the procedure. Twenty-seven patients (18%) developed OI. The relative decrease in NIRS oximeter saturation (ΔrSO₂) on the ipsilateral side was significantly lower in the OI group than in the tolerance group (14 ± 5.1% vs. 3.4 ± 3.5, p < 0.001). Using ΔrSO₂ of 8% as the cutoff value for predicting OI, sensitivity was 92% and specificity was 89%. SP was significantly lower in the OI group than in the tolerance group (22 ± 13 mmHg vs. 40 ± 22 mmHg, p < 0.001). Using SP ≤25 mmHg as the cutoff value for predicting OI, sensitivity was 78% and specificity was 77%. ΔrSO₂ was more reliable than SP for predicting OI. Distal filter protection should be combined with proximal protection to prevent prolonged neurological symptoms due to OI.

Safety of perioperative cerebral oxygen saturation during debranching in patients with incomplete circle of Willis

OBJECTIVES

The consequences of common carotid artery (CCA) cross-clamping during debranching before thoracic endovascular aortic repair are unclear. We examined the safety of a simple CCA cross-clamping procedure under regional cerebral oxygen saturation monitoring (rSO2) in patients with a complete or incomplete circle of Willis (CoW) anatomy.

METHODS

Twenty-eight patients with thoracic aneurysm underwent elective debranching thoracic endovascular aortic repair with bilateral frontal rSO2 monitoring at our institution between January 2012 and October 2015. Before CCA cross-clamping, we maintained a systemic mean arterial pressure of >100 mm Hg with a vasopressor. We recorded the bilateral frontal rSO2 before, during and after CCA cross-clamping.

RESULTS

The CoW was incomplete in 11 (39.3%) patients. Of these, 6 patients had a complication of ischaemic potential. The left frontal rSO2 was <50% in 3 patients but did not fall below 40%. Compared with baseline values (mean ± SD 64.6 ± 6.9%), the left frontal rSO2 showed no significant change perioperatively in those with a complete CoW on the left CCA cross-clamping (during: 61.0 ± 7.9%, P = 0.17; after: 65.1 ± 5.9%, P = 0.09). In patients with an incomplete CoW with ischaemic potential, the left frontal rSO2 did not change significantly after cross-clamping (baseline: 59.8 ± 3.2%, during: 55.5 ± 5.0%; P = 0.10) but increased significantly on declamping (62.8 ± 4.5%, P = 0.023). The extent of the changes in the mean left frontal rSO2 on clamping and declamping decreased and increased by 7.3% and 11.7%, respectively, in patients with an incomplete CoW, when compared with 5.3% and 5.8% in those with a complete CoW (P = 0.65 and 0.31, respectively). No perioperative cerebrovascular events were observed.

CONCLUSIONS

Simple CCA cross-clamping during debranching was safe when arterial pressure was supported and rSO2 was monitored, even with an incomplete CoW and ischaemic potential.

Cerebral Neuromonitoring during Carotid Endarterectomy and Impact of Contralateral Internal Carotid Occlusion

BACKGROUND

The aim of this study was to identify the reliability of carotid artery stump pressure (SP) in predicting the neurologic changes and correlation with contralateral internal carotid artery (ICA) occlusion in patients undergoing eversion carotid endarterectomy (CEA). The optimal method for monitoring cerebral perfusion during CEA, performed under either local or general anesthesia, is still controversial.

METHODS

We prospectively analyzed 118 consecutive patients undergoing eversion CEA under local anesthesia. We had 78 symptomatic (66%) and 40 asymptomatic patients (33.9%). Selective shunting was performed in patients who developed neurologic changes after carotid clamping regardless of SP. Correlation of preoperative symptom status, a degree of stenosis, status of contralateral ICA, arterial blood pressure, SP value, and the intraoperative need for shunting due to neurologic changes was evaluated for both groups: shunted and nonshunted.

RESULTS

Selective shunting was performed in 12 patients (10%). There was no significant difference among the groups regarding the demographic characteristics. Mean carotid clamping time was 14.57 minutes. We had no perioperative mortality, stroke, or myocardial infarction. None of the patients required conversion to general anesthesia. We found a mean SP of 31 mm Hg as a reliable threshold for shunting (P < .001; sensitivity 92.3%; specificity 91.3%). Contralateral carotid occlusion was correlated with the significantly lower SP (27 ± 13 mm Hg; P = .001) and the higher need for shunt (50%).

CONCLUSIONS

SP measurement is a reliable and simple method for monitoring the collateral cerebral perfusion and can predict the need for shunting during CEA. Patients with the contralateral ICA occlusion showed significantly lower SP, although it did not have impact on the outcome.

Anesthetic Considerations for Carotid Endarterectomy: A Postgraduate Educational Review

Carotid endarterectomy (CEA) has shown a significant benefit in preventing ipsilateral stroke when it is compared to conservative management. Surgical morbidity and mortality must be kept to a minimum to achieve this benefit. Neurological status of the CEA patients can be monitored easily during regional anesthesia depending on the awake testing (neurocognitive assessment) method of the CEA patients. In addition, specific parameters can help us to monitor and to predict the neurological status of the CEA patients during the procedures such as regional cerebral oxygen saturation (rSO₂) and middle cerebral artery velocity (MCAv) changes. We conducted a computerized literature search involving humans, published in English until December 2017, and indexed through Medical Databases; MEDLINE/PubMed, EMBASE, and Web of Science. We reviewed articles performed for prospective and other types of studies related to CEA procedures and techniques which can predict patient's status during the procedure. Searching relevant articles and discussing the results to allow meaningful rate comparison, and to conclude a result view which benefits the CEA patients and the medical staff during the CEA procedures. In total, studies observed cerebral rSO₂ and MCAv have significant value during CEA procedures. Patients with neurological symptoms during the procedures showed changes of cerebral rSO₂ and MCAv more than the patients without neurological symptoms. Mentioned parameters (cerebral rSO₂ and MCAv) showed significant increasing right after the procedure. Mostly, CEA surgeries under local anesthesia were observed, for monitoring patients' consciousness status and comparing it to patients who undergo general anesthesia, to view the reliability of these techniques during CEA procedures, and to predict and avoid intraoperative neurological symptoms.

Quantifying cerebral hypoxia by near-infrared spectroscopy tissue oximetry: the role of arterial-to-venous blood volume ratio

Tissue oxygenation estimated by near-infrared spectroscopy (NIRS) is a volume-weighted mean of the arterial and venous hemoglobin oxygenation. In vivo validation assumes a fixed arterial-to-venous volume-ratio (AV-ratio). Regulatory cerebro-vascular mechanisms may change the AV-ratio. We used hypotension to investigate the influence of blood volume distribution on cerebral NIRS in a newborn piglet model. Hypotension was induced gradually by inflating a balloon-catheter in the inferior vena cava and the regional tissue oxygenation from NIRS ( rStO 2 , NIRS ) was then compared to a reference ( rStO 2 , COX ) calculated from superior sagittal sinus and aortic blood sample co-oximetry with a fixed AV-ratio. Apparent changes in the AV-ratio and cerebral blood volume (CBV) were also calculated. The mean arterial blood pressure (MABP) range was 14 to 82 mmHg. PaCO 2 and SaO 2 were stable during measurements. rStO 2 , NIRS mirrored only 25% (95% Cl: 21% to 28%, p < 0.001 ) of changes in rStO 2 , COX . Calculated AV-ratio increased with decreasing MABP (slope: ? 0.007 · mmHg ? 1

S100B concentrations increase perioperatively in jugular vein blood despite limited metabolic and inflammatory response to clinically uneventful carotid endarterectomy

Our aim was to test the hypothesis that metabolic and inflammatory responses of the brain perioperatively during carotid endarterectomy (CEA) might affect blood brain barrier (BBB) integrity.

Twenty patients with >70% stenosis of internal carotid artery (ICA) were prospectively included. Surgery was performed under general anaesthesia. Blood was sampled from ipsilateral internal jugular vein and radial artery: just before, during, and after ICA clamping S100B protein, glucose, lactate, 20 amino acids, and key cytokines were analysed.

Jugular vein S100B increased during clamping and reperfusion, while a marginal systemic increase was recorded, unrelated to stump pressure during clamping. Glucose increased during clamping in jugular vein blood and even more systemically, while jugular lactate values were higher than systemic values initially. Most amino acids did not differ significantly between jugular vein and systemic levels: glutamic acid and aspartic acid decreased during surgery while asparagine increased. Jugular vein interleukin (IL)-6 showed a transient non-significant increase during clamping and decreased systemically. IL-8 and IL-10 increased over time.

Rising jugular vein S100B concentrations indicated reduced BBB integrity, and marginal secondary increase of S100B systemically. Limited ischaemic effects on the brain during cross-clamping, unrelated to S100B concentrations, were confirmed by lower brain glucose levels and higher lactate levels than in systemic blood. The lack of increased jugular vein glutamic acid disproves any major ischaemic brain injury following CEA. The inflammatory response was limited, did not differ greatly between jugular and systemic blood, and was unrelated to S100B.

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.

Carotid endarterectomy using a "home-constructed" shunt for patients intolerant to cross-clamping

PURPOSES

There is a small minority of patients with occlusive carotid artery disease, who are at high-risk for general anesthesia because of their intolerance to carotid flow blockage, even if only for seconds, without neurologic deficit. Even <30 s of temporary clamping of the carotid arteries to deploy a shunt may prove eventful in this patient group. We define safe carotid endarterectomy after the insertion of a novel shunt that we made from simple medical equipment in this patient population.

METHODS

Among 65 patients who underwent carotid endarterectomy between March 2010 and December 2012, 5 (7.7 %; 3 men and 2 women; age range 56-77 years) could not tolerate carotid clamping. We used an alternative carotid shunt, made by us from simple equipment in our clinic, during surgery for these patients.

RESULTS

Two patients had bilateral lesions and the remainder had unilateral disease. The degree of stenosis ranged from 70 to 95 %. Temporary carotid clamping resulted in neurologic events, such as loss of consciousness in all and tremor in one, in <10 s (range, from immediately to 8 s after clamping). Full neurologic function was regained 15-30 s after releasing the clamps. All of the patients tolerated the procedures well with the support of our novel shunt. Shunt flow was adequate in all patients and no neurologic deterioration occurred after carotid clamping. The mean carotid clamp time was 28.11 ± 14.19 min. There was no mortality and all patients were followed up for a mean period of 9.3 ± 3.6 months, uneventfully.

CONCLUSIONS

An alternative, simple shunt, which is easily constructed in the operating room or clinic, using an angiocatheter, a three-way stopcock, and a serum line can provide adequate cerebral flow and permit safe carotid endarterectomy for those rare patients with carotid artery stenosis, who cannot tolerate even seconds of carotid occlusion.

Systematic review of near-infrared spectroscopy determined cerebral oxygenation during non-cardiac surgery

Near-infrared spectroscopy (NIRS) is used to monitor regional cerebral oxygenation (rScO₂) during cardiac surgery but is less established during non-cardiac surgery. This systematic review aimed (i) to determine the non-cardiac surgical procedures that provoke a reduction in rScO₂ and (ii) to evaluate whether an intraoperative reduction in rScO₂ influences postoperative outcome. The PubMed and Embase database were searched from inception until April 30, 2013 and inclusion criteria were intraoperative NIRS determined rScO₂ in adult patients undergoing non-cardiac surgery. The type of surgery and number of patients included were recorded. There was included 113 articles and evidence suggests that rScO₂ is reduced during thoracic surgery involving single lung ventilation, major abdominal surgery, hip surgery, and laparoscopic surgery with the patient placed in anti-Tredelenburg's position. Shoulder arthroscopy in the beach chair and carotid endarterectomy with clamped internal carotid artery (ICA) also cause pronounced cerebral desaturation. A >20% reduction in rScO₂ coincides with indices of regional and global cerebral ischemia during carotid endarterectomy. Following thoracic surgery, major orthopedic, and abdominal surgery the occurrence of postoperative cognitive dysfunction (POCD) might be related to intraoperative cerebral desaturation. In conclusion, certain non-cardiac surgical procedures is associated with an increased risk for the occurrence of rScO₂. Evidence for an association between cerebral desaturation and postoperative outcome parameters other than cognitive dysfunction needs to be established.

Use of the vascu-guard bovine pericardium patch for arteriotomy closure in carotid endarterectomy. Early and long-term results

BACKGROUND

To report the early and long-term results of Vascu-Guard bovine pericardium (BP) for patch angioplasty in carotid endarterectomy (CEA).

METHODS

We retrospectively analyzed the data of 256 CEAs with BP patch closure performed in 238 patients during the past 12 years in our department. Patch-related complications (restenosis, infection, and aneurysm formation) and early and late (12 to 144 months follow-up) clinical outcomes were recorded and statistically analyzed.

RESULTS

Thirty-day postoperative stroke rate was 1.2% (3/256) with zero mortality. Major complications occurred in 3.5% (9 of 256) of the procedures and cranial nerve injury in 4.3% (11 of 256). At 12 years, cumulative estimates of freedom from any stroke, stroke-free survival, and freedom from restenosis were 88.4% (standard error [SE]: 3.3%), 60% (SE: 7.8%), and 98.3% (SE: 0.8%), respectively. No patient experienced patch infection or aneurysm formation.

CONCLUSIONS

This series shows the efficacy, safety, and durability of CEA with BP patch closure, in both the short and long term. BP combines the advantages of vein and synthetic patches, representing a suitable option when performing CEA.

Research studies that have influenced practice of neuroanesthesiology in recent years: A literature review

Through evolving research, recent years have witnessed remarkable achievements in neuromonitoring and neuroanesthetic techniques, with a huge body of literature consisting of excellent studies in neuroanaesthesiology. However, little of this work appears to be directly important to clinical practice. Many controversies still exist in care of patients with neurologic injury. This review discusses studies of great clinical importance carried out in the last five years, which have the potential of influencing our current clinical practice and also attempts to define areas in need of further research. Relevant literature was obtained through multiple sources that included professional websites, medical journals and textbooks using key words “neuroanaesthesiology,” “traumatic brain injury,” “aneurysmal subarachnoid haemorrhage,” “carotid artery disease,” “brain protection,” “glycemic management” and “neurocritical care.” In head injured patients, administration of colloid and pre-hospital hypertonic saline resuscitation have not been found beneficial while use of multimodality monitoring, individualized optimal cerebral perfusion pressure therapy, tranexamic acid and decompressive craniectomy needs further evaluation. Studies are underway for establishing cerebroprotective potential of therapeutic hypothermia. Local anaesthesia provides better neurocognitive outcome in patients undergoing carotid endarterectomy compared with general anaesthesia. In patients with aneurysmal subarachnoid haemorrhage, induced hypertension alone is currently recommended for treating suspected cerebral vasospasm in place of triple H therapy. Till date, nimodipine is the only drug with proven efficacy in preventing cerebral vasospasm. In neurocritically ill patients, intensive insulin therapy results in substantial increase in hypoglycemic episodes and mortality rate, with current emphasis on minimizing glucose variability. Results of ongoing multicentric trials are likely to further improvise our practice.

Neurophysiologic monitoring in neurosurgery

This article focuses on the application of neurophysiologic monitoring in uniquely neurosurgical procedures. Neurophysiologic monitoring provides functional testing and mapping to identify neural structures. Once identified, the functionality of the central and peripheral nervous system areas at risk for neurosurgical injury can be monitored. It discusses the use of motor-evoked potentials, sensory evoked potentials, electromyography and electroencephalography to assess neurologic change.