Comparison of monitoring techniques for intraoperative cerebral ischemia

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

OBJECTIVE

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

DATA SOURCES

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Intraoperative Cerebral Hemodynamic Monitoring during Carotid Endarterectomy via Diffuse Correlation Spectroscopy and Near-Infrared Spectroscopy

Objective: This pilot study aims to show the feasibility of noninvasive and real-time cerebral hemodynamic monitoring during carotid endarterectomy (CEA) via diffuse correlation spectroscopy (DCS) and near-infrared spectroscopy (NIRS). Methods: Cerebral blood flow index (CBFi) was measured unilaterally in seven patients and bilaterally in seventeen patients via DCS. In fourteen patients, hemoglobin oxygenation changes were measured bilaterally and simultaneously via NIRS. Cerebral autoregulation (CAR) and cerebrovascular resistance (CVR) were estimated using CBFi and arterial blood pressure data. Further, compensatory responses to the ipsilateral hemisphere were investigated at different contralateral stenosis levels. Results: Clamping of carotid arteries caused a sharp increase of CVR (~70%) and a marked decrease of ipsilateral CBFi (57%). From the initial drop, we observed partial recovery in CBFi, an increase of blood volume, and a reduction in CVR in the ipsilateral hemisphere. There were no significant changes in compensatory responses between different contralateral stenosis levels as CAR was intact in both hemispheres throughout the CEA phase. A comparison between hemispheric CBFi showed lower ipsilateral levels during the CEA and post-CEA phases (p < 0.001, 0.03). Conclusion: DCS alone or combined with NIRS is a useful monitoring technique for real-time assessment of cerebral hemodynamic changes and allows individualized strategies to improve cerebral perfusion during CEA by identifying different hemodynamic metrics.

Monitoring in carotid endarterectomy

Cerebral ischemia during carotid endarterectomy occurs via several mechanisms: inadequate collateral blood flow during carotid cross-clamping, thromboembolism due to carotid manipulation, and/or rethrombosis at the surgical site. Perioperative strokes increase not only the morbidity of endarterectomy but also its short- and long-term mortality. However, while several predictors of cerebral ischemia have been identified, precise individual risk is hard to assess. Since nonselective shunting during carotid cross-clamping is neither risk-free nor eliminates perioperative stroke, it is advisable to apply intraoperative monitoring techniques for detection and reversal of cerebral ischemia, which may occur at various stages of the procedure. This chapter addresses the methods available for monitoring, with an emphasis on neurophysiologic techniques, which are preferable given their direct assessment of how a decrease in cerebral blood flow impacts brain function. These include electroencephalography, somatosensory evoked potentials, and transcranial motor evoked potentials. Details regarding the methodology, advantages, disadvantages, and interpretation of these tests will be discussed within the anatomic, physiologic, surgical, and anesthetic contexts.

Processed Multiparameter Electroencephalogram-Guided General Anesthesia Management Can Reduce Postoperative Delirium Following Carotid Endarterectomy: A Randomized Clinical Trial

Background: Patients undergoing carotid endarterectomy (CEA) for severe carotid stenosis are vulnerable to postoperative delirium, a complication frequently associated with poor outcome. This study investigated the impact of processed electroencephalogram (EEG)-guided anesthesia management on the incidence of postoperative delirium in patients undergoing CEA.

Methods: This single-center, prospective, randomized clinical trial on 255 patients receiving CEA under general anesthesia compared the outcomes of patient state index (PSI) monitoring [SEDLine Brain Function Monitor (Masimo, Inc, Irvine, CA)] (standard group, n = 128) with PSI combined with density spectral array(DSA) -guided monitoring (intervention group, n = 127) to reduce the risk of intraoperative EEG burst suppression. All patients were monitored by continuous transcranial Doppler ultrasound (TCD) and near-infrared spectroscopy (NIRS) to avoid perioperative cerebral hypoperfusion or hyperperfusion. According to the surgical process, EEG suppression time was calculated separately for three stages: S₁ (from anesthesia induction to carotid artery clamping), S₂ (from clamping to declamping), and S₃ (from declamping to the end of surgery). The primary outcome was incidence of postoperative delirium according to the Confusion Assessment Method algorithm during the first 3 days post-surgery, and secondary outcomes were other neurologic complications and length of hospital stay.

Results: There were no episodes of cerebral hypoperfusion or hyperperfusion according to TCD and NIRS monitoring in either group during surgery. The incidence of postoperative delirium within 3 days post-surgery was significantly lower in the intervention group than the standard group (7.87 vs. 28.91%, P < 0.01). In the intervention group, the total EEG suppression time and the EEG suppression time during S2 and S3 were shorter (Total, 0 “0” vs. 0 “1.17” min, P = 0.04; S₂, 0 “0” vs. 0 “0.1” min, P < 0.01; S₃, 0 “0” vs. 0 “0” min, P = 0.02). There were no group differences in incidence of neurologic complications and length of postoperative hospital stay.

Conclusion: Processed electroencephalogram-guided general anesthesia management, consisting of PSI combined with DSA monitoring, can significantly reduce the risk of postoperative delirium in patients undergoing CEA. Patients, especially those exhibiting hemodynamic fluctuations or receiving surgical procedures that disrupt cerebral perfusion, may benefit from the monitoring of multiple EEG parameters during surgery.

Clinical Trial Registration:www.ClinicalTrials.gov, identifier: NCT03622515.

Unanticipated Disturbance in Somatosensory Evoked Potentials in a Patient in Park-Bench Position

Perioperative neuropathy is a known complication of malpositioning during anaesthesia. Somatosensory evoked potentials are used for detecting such a complication in selected surgeries. Most reports of intraoperative nerve injuries due to malpositioning are limited to injuries to the peripheral nervous system, and there have been no previously reported cases of somatosensory evoked potential monitoring disturbance attributable to position-related cerebral ischemia in the park-bench position. We present the case of a patient with glioblastoma in the park-bench position whose somatosensory evoked potential waveforms disappeared after head and neck repositioning. A prompt diagnosis of this complication and elimination of the underlying cause led to the return of somatosensory evoked potential waveforms, and there was no relevant neurologic deficit at the end of the surgery.

Monitoring cerebral ischemia during carotid endarterectomy and stenting

Current therapy for carotid stenosis mainly includes carotid endarterectomy and endovascular stenting, which may incur procedure-related cerebral ischemia. Several methods have been employed for monitoring cerebral ischemia during surgery, such as awake neurocognitive assessment, electroencephalography, evoked potentials, transcranial Doppler, carotid stump pressure, and near infrared spectroscopy. However, there is no consensus on the gold standard or the method that is superior to others at present. Keeping patient awake for real time neurocognitive assessment is effective and essential; however, not every surgeon adopts it. In patients under general anesthesia, cerebral ischemia monitoring has to rely on non-awake technologies. The advantageous and disadvantageous properties of each monitoring method are reviewed.

[Complications after supra-aortic reconstruction]

BACKGROUND

Surgical interventions on the supra-aortic vessels are common procedures to avoid cerebral ischemia or arm pain during exercise. The safety and efficacy has been confirmed by clinical studies. Complications are rare but have serious consequences.

OBJECTIVES

What special indications and recommendations are there for the diagnostics and treatment in the perioperative phase?

METHODS

The current article is a literature-based review that considers international studies, guidelines and personal experiences.

RESULTS

There is a broad range of complications. A simple systematic physical examination is often sufficient to give indications of the problem. Confirming clinical apparative examinations are mostly intraoperative angiography or sonography, whereas postoperative procedures include color-coded duplex sonography (FKDS) and angiography computed tomography (angio-CT). Important basic principles and aspects of operative procedures are presented. Evidence-based differences between the treatment options with resulting complications are mostly unknown; therefore, clinical management mostly relies on expert recommendations.

CONCLUSION

There are several modern treatment options for invasive therapy. Despite a decrease in previous complication rates, typical perioperative complications must be considered. The diagnosis and therapy is carried out according to established strategies.

Stratification of intraoperative ischemic impact by somatosensory evoked potential monitoring, diffusion-weighted imaging and magnetic resonance angiography in carotid endarterectomy with routine shunt use

BACKGROUND

Routine shunting to minimize ischemia during carotid endarterectomy (CEA) is controversial. The aim of this study was to stratify the ischemic parameters associated with CEA and evaluate the effect of routine shunting in attempting to mitigate those ischemia.

METHOD

Data from 248 CEAs with routine shunting were retrospectively evaluated. Our assessment included somatosensory evoked potential (SSEP) amplitude reduction more than 50 % and longer than 5 min (SSEP<50%, >5 min), new postoperative diffusion-weighted imaging lesions (new DWI lesions), and severe stenosis as indicated by reduced ipsilateral middle cerebral artery (MCA) signal on preoperative magnetic resonance angiography (MRA asymmetry), as surrogates of hypoperfusion, microembli, and hemodynamic impairment, respectively.

RESULTS

SSEP<50%, >5 min occurred in 15 % of CEAs during cross-clamping, and shunting reversed the SSEP changes. New DWI lesions were observed in 4.1 %. Pre-clamping the common and external carotid artery during dissection (pre-clamp method) decreased the rate of new DWI lesions compared to without pre-clamping (3.5 % vs. 7.5 %, P = 0.22). Occlusion time was significantly longer in the pre-clamp method than without pre-clamping (P < 0.0001). However, the incidence of SSEP<50%, >5 min was not increased with the pre-clamp method (p = 1.0) when using information regarding SSEP and collaterals to modify the speed of shunt manipulation. MRA asymmetry was identified in 39 CEAs (15.8 %) with correction of asymmetry postoperatively. MRA asymmetry correlated with symptomatic hyperperfusion (P = 0.0034). Only three CEAs had symptomatic hyperperfusion (1.2 %) with minimal symptoms. Ten CEAs sustained transient ischemia, symptomatic hyperperfusion, or 30-day-stroke (composite postoperative ischemic symptoms). Logistic regression analysis confirmed that SSEP<50%, >5 min (p = 0.009), new DWI lesions (p = 0.004) and MRA asymmetry (p = 0.042) were independent predictors of　composite postoperative ischemic symptoms.

CONCLUSIONS

SSEP<50%, >5 min, new DWI lesions, and MRA asymmetry were able to stratify the ischemic impacts in CEA. Meticulous routine shunting could mitigate those appropriately.

Subclinical ischemia verified by somatosensory evoked potential amplitude reduction during carotid endarterectomy: negative effects on cognitive performance

OBJECT

Although the mechanisms underlying neurocognitive changes after carotid endarterectomy (CEA) are poorly understood, intraoperative ischemia and postoperative hemodynamic changes may play a role.

METHODS

Data from 81 patients who underwent unilateral CEA with routine shunt use for carotid artery stenosis were retrospectively evaluated. These patients underwent neuropsychological examinations (NPEs), including assessment by the Wechsler Adult Intelligence Scale-Third Edition and the Wechsler Memory Scale-Revised before and 6 months after CEA. results of NPEs were converted into z scores, from which pre- and postoperative cognitive composite scores (CSpre and CSpost) were obtained. The association between the change of CS between pre- and postoperative NPEs (that is, CSpost - CSpre [CSpost - pre]) and various variables was assessed. These latter variables included ischemic or hemodynamic parameters such as 1) intraoperative hypoperfusion detected by somatosensory evoked potential (SSEP) change-that is, an SSEP amplitude reduction more than 50% and longer than 5 minutes (SSEP< 50%, > 5 min); 2) new lesions on postoperative diffusion-weighted imaging studies; and 3) preexisting hemodynamic impairment. Paired t-tests of the NPE scores were performed to determine the net effect of these factors on neurocognitive function at 6 months.

RESULTS

A significant CSpost - pre decrease was observed in patients with SSEP< 50%, > 5 min when compared with those without SSEP< 50%, > 5 min (-0.225 vs 0.018; p = 0.012). Multiple regression analysis demonstrated that SSEP< 50%, > 5 min independently and negatively correlated with CSpost - pre (p = 0.0020). In the group-rate analysis, postoperative NPE scores were significantly improved relative to preoperative scores.

CONCLUSIONS

Hypoperfusion during cross-clamping, as verified by SSEP amplitude reduction, plays a significant role in the subtle decline in cognition following CEA. However, this detrimental effect was small, and various confounding factors were present. Based on these observations and the group-rate analysis, the authors conclude that successful unilateral CEA with routine shunt use does not adversely affect postoperative cognitive function.

[Intraoperative electrophysiological monitoring with evoked potentials]

During the last 30 years intraoperative electrophysiological monitoring (IOEM) has gained increasing importance in monitoring the function of neuronal structures and the intraoperative detection of impending new neurological deficits. The use of IOEM could reduce the incidence of postoperative neurological deficits after various surgical procedures. Motor evoked potentials (MEP) seem to be superior to other methods for many indications regarding monitoring of the central nervous system. During the application of IOEM general anesthesia should be provided by total intravenous anesthesia with propofol with an emphasis on a continuous high opioid dosage. When intraoperative MEP or electromyography guidance is planned, muscle relaxation must be either completely omitted or maintained in a titrated dose range in a steady state. The IOEM can be performed by surgeons, neurologists and neurophysiologists or increasingly more by anesthesiologists. However, to guarantee a safe application and interpretation, sufficient knowledge of the effects of the surgical procedure and pharmacological and physiological influences on the neurophysiological findings are indispensable.

Cerebral monitoring during carotid endarterectomy using near-infrared diffuse optical spectroscopies and electroencephalogram

Intraoperative monitoring of cerebral hemodynamics during carotid endarterectomy (CEA) provides essential information for detecting cerebral hypoperfusion induced by temporary internal carotid artery (ICA) clamping and post-CEA hyperperfusion syndrome. This study tests the feasibility and sensitivity of a novel dual-wavelength near-infrared diffuse correlation spectroscopy technique in detecting cerebral blood flow (CBF) and cerebral oxygenation in patients undergoing CEA. Two fiber-optic probes were taped on both sides of the forehead for cerebral hemodynamic measurements, and the instantaneous decreases in CBF and electroencephalogram (EEG) alpha-band power during ICA clamping were compared to test the measurement sensitivities of the two techniques. The ICA clamps resulted in significant CBF decreases (-24.7 ± 7.3%) accompanied with cerebral deoxygenation at the surgical sides (n = 12). The post-CEA CBF were significantly higher (+43.2 ± 16.9%) than the pre-CEA CBF. The CBF responses to ICA clamping were significantly faster, larger and more sensitive than EEG responses. Simultaneous monitoring of CBF, cerebral oxygenation and EEG power provides a comprehensive evaluation of cerebral physiological status, thus showing potential for the adoption of acute interventions (e.g., shunting, medications) during CEA to reduce the risks of severe cerebral ischemia and cerebral hyperperfusion syndrome.

[The carotid artery as recipient vessel: troubleshooting for free jejunal transfer after esophagectomy in preradiated patients]

BACKGROUND

In the treatment of esophageal cancer neoadjuvant radiotherapy often leads to vascular damage of the usual recipient arteries for free jejunal transfer. End-to-side anastomosis to the carotid artery could be a potential alternative.

PATIENTS AND METHODS

A total of 70 patients with locally advanced carcinoma of the esophagus underwent esophagectomy after neoadjuvant radiochemotherapy. In all patients reconstruction was carried out with a free jejunal transfer. Smaller vessels could be used for anastomoses in 54 of these patients and in 16 cases the jejunal flap artery was attached to the carotid artery.

RESULTS

Out of 54 patients 9 (17%) with microvascular anastomoses to the smaller vessels needed surgical intervention for ischemia. In 16 patients with anastomosis to the carotid artery no significant failure of perfusion occurred.

CONCLUSION

The carotid artery as recipient vessel in free jejunal transfer seems to be a safe therapeutic option for intestinal reconstruction of preradiated esophageal cancer with good functional results.

Electrophysiology and neuronal integrity following systemic arterial hypotension in a rat model of unilateral carotid artery occlusion

Patients with carotid artery stenosis may be particularly susceptible to hypotension-associated cerebral ischemia and subsequent neurological sequelae. Measuring somatosensory evoked potentials (SEP), electroencephalogram (EEG), direct current (DC) potential, and histology, we compared the temporal evolution of cortical functional perturbations as well as neuronal integrity in a model of unilateral carotid artery occlusion and systemic hypobaric hypotension (HH) at the lower limit of cerebral blood flow autoregulation (50 mm Hg). Serial measurements of EEG power spectra as well as SEP-amplitudes and latencies of N10.3 were performed before, during, and up to 60 min after 30 min-HH (n=7) or the control condition (n=7) in male Wistar rats. In two additional groups (with [n=7] or without [n=7] HH), cortical spreading depressions (CSD) were elicited to ascertain their contribution to brain injury. Hematoxilin-Eosin (H&E) staining was used to assess neuronal cell death at 5 days after surgery. Relative to baseline, HH attenuated ipsilateral EEG power spectrum (by maximally 62%), increased SEP-latencies (by approximately 6-10%) and amplitudes (by approximately 57-70%), and induced selective neuronal cell death in the cerebral cortex and hippocampus (P<0.05 vs. contralateral). Spontaneous CSD occurred in approximately 30% of HH-animals. Repolarization of the DC-potential during HH was significantly prolonged relative to normotensive conditions (10.3+/-11.5 min, P<0.001). Our model may help to understand underlying pathophysiology and improve outcome in a clinical subset of patients with carotid artery stenosis and transient systemic hypotension.

Experience of 500 cases of neurophysiological monitoring in carotid endarterectomy

BACKGROUND

Experience with Intraoperative monitoring using neurophysiological and haemodynamic indices in 500 operations for carotid endarterectomy is reported.

METHODS

Transcranial Doppler technique (TCD), electroencephalogram (EEG) and bilateral median somatosensory evoked potentials (SEP) were performed. Latency and amplitude of SEP, spectral analysis of EEG signal and blood flow velocity in the medial cerebral artery (MCA) were continuously measured.

FINDINGS

After two consecutive drops of N20/P25 complex of more than 50%, a warning was given, and when the decrease continued, an the alarm raised. Abnormal EEG changes, if any, appeared after a significant decrease in the N20/P25 amplitude. A mean blood flow velocity drop below 40% of the reference value after cross clamping was rated as a significant warning event.A warning as a result of a decrease in N20/P25 amplitude occurred in 80 operations (16.0%), after an spectral edge frequency decrease in 2 cases (0.4%) and after a V(mean) decrease in 21 cases (4.2%). False negative results were experienced in 2 patients (0.4%). A shunt was inserted in 2.8% of the operations. The overall mortality/morbidity rate was 2.4%.

CONCLUSION

A decrease of more than 50% in the amplitude of the thalamocortical somatosensory evoked potential complex N20/P25 proved to be the most reliable warning of danger of ischaemia during carotid endarterectomy.

Staged anesthesia for combined carotid and coronary artery revascularization: a different approach

OBJECTIVE

Combined coronary artery bypass graft (CABG) surgery and carotid endarterectomy (CEA) are performed in an attempt to reduce the risk of postoperative stroke after CABG surgery in patients with significant or symptomatic carotid artery stenosis. The choice between regional and general anesthesia for CEA is still under debate. Regional anesthesia offers an excellent monitoring technique of the neurologic status of the awake patient during carotid clamping. In an attempt to improve monitoring of the neurologic status and avoid the use of temporary shunting in patients undergoing the combined procedure, a different approach is described combining regional anesthesia for CEA followed immediately by general anesthesia for CABG surgery.

DESIGN

Prospective nonrandomized case series.

SETTING

University hospital.

PARTICIPANTS

Twenty patients scheduled for combined CEA and CABG surgery underwent a "staged" anesthetic approach from January to December 2004.

INTERVENTIONS

Pulmonary, femoral artery, and urinary catheters were inserted under local anesthesia. A deep cervical plexus block was then performed and supplemented by a superficial cervical plexus block. The patient was draped for standard combined CEA and CABG surgery. CEA was then performed using standard techniques. Without altering the surgical field, general anesthesia was given and endotracheal intubation performed following the successful CEA. Coronary revascularization was then completed.

MEASUREMENTS AND MAIN RESULTS

CEA and CABG surgery were completed successfully in all patients. There was no need for conversion from local to general anesthesia. Endotracheal intubation was easily performed in all patients. There was no hospital mortality in this series. No neurologic events were observed during the CEA. A reversible ischemic stroke, ipsilateral to the CEA, occurred postoperatively on awakening from CABG surgery in 1 patient.

CONCLUSIONS

This staged anesthetic approach for combined CABG and CEA surgery is an alternative in this complex subset of patients.