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

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.

Effect of Extracerebral Contamination on Near-infrared Spectroscopy as Revealed during Organ Donation: A Prospective Observational Study in Brain-dead Organ Donors

BACKGROUND

Near-infrared spectroscopy (NIRS) has been utilized widely in anesthesia and intensive care to monitor regional cerebral oxygen saturation (rScO2). A normal oxygenation of extracerebral tissues may overlay and thereby mask cerebral desaturations, a phenomenon known as extracerebral contamination. The authors investigated the effect of a cessation of extracerebral tissue perfusion on rScO2 in patients with anoxic brains.

METHODS

In a single-center, prospective, observational study, brain-dead adults undergoing organ donation were investigated. rScO2 was measured bifrontally using the INVOS 5100C/7100 as well as the ForeSight Elite system. To achieve an efficient conservation of organs and to prevent a redistribution of the perfusion fluid to other tissues, the aorta was clamped before organ perfusion. rScO2 was monitored until at least 40 min after aortic clamping. The primary outcome was the amount of extracerebral contamination as quantified by the absolute decrease in rScO2 after aortic clamping. Secondary outcomes were the absolute rScO2 values obtained before and after clamping.

RESULTS

Twelve organ donors were included. Aortic clamping resulted in a significantly (P < 0.001) greater absolute decrease in rScO2 when comparing the INVOS (43.0 ± 9.5%) to the ForeSight (27.8 ± 7.1%) monitor. Before aortic clamping, near-normal rScO2 values were obtained by the INVOS (63.8 ± 6.2%) and the ForeSight monitor (67.7 ± 6.5%). The rScO2 significantly (P < 0.001) dropped to 20.8 ± 7.8% (INVOS) and 39.9 ± 8.1% (ForeSight) 30 min after clamping, i.e., a condition of a desaturation of both extracerebral and cerebral tissues.

CONCLUSIONS

The abrupt end of extracerebral contamination, caused by aortic clamping, affected both NIRS monitors to a considerable extent. Both the INVOS and the ForeSight monitor were unable to detect severe cerebral hypoxia or anoxia under conditions of normal extracerebral oxygenation. While both NIRS monitors may guide measures to optimize arterial oxygen supply to the head, they should not be used with the intention to detect isolated cerebral desaturations.

EDITOR’S PERSPECTIVE

Combined Arterial Hypertension and Ischemic Stroke Exaggerate Anesthesia-Related Hypotension and Cerebral Oxygenation Deficits: A Preclinical Study

BACKGROUND

Intraoperative arterial hypotension (IOH) is a common side effect of general anesthesia (GA), associated with poor outcomes in ischemic stroke. While IOH is more prevalent with hypertension, it is unknown whether IOH may differ when GA is induced during ischemic stroke, versus other clinical settings. This is important given that many stroke patients receive GA for endovascular thrombectomy.

METHODS

We evaluate the cardiovascular responses to volatile GA (isoflurane in 100% o2 ) before and during middle cerebral artery occlusion stroke in rats instrumented to record blood pressure (BP) and cerebral tissue oxygenation (p o2 ) in the projected penumbra, in clinically relevant cohorts of normotensive (Wistar rat, n = 10), treated hypertensive (spontaneously hypertensive [SH] + enalapril, n = 12), and untreated hypertensive (SH rat, n = 12).

RESULTS

During baseline induction of GA, IOH was similar in normotensive, treated hypertensive, and untreated hypertensive rats during the induction phase (first 10 minutes) (-24 ± 15 vs -28 ± 22 vs -48 ± 24 mm Hg; P > .05) and across the procedure (-24 ± 13 vs -30 ± 35 vs -39 ± 27 mm Hg; P > .05). Despite the BP reduction, cerebral p o2 increased by ~50% in all groups during the procedure. When inducing GA after 2 hours, all stroke groups showed a greater magnitude IOH compared to baseline GA induction, with larger falls in treated (-79 ± 24 mm Hg; P = .0202) and untreated(-105 ± 43 mm Hg; P < .001) hypertensive rats versus normotensives (-49 ± 21 mm Hg). This was accompanied by smaller increases in cerebral p o2 in normotensive rats (19% ± 32%; P = .0144 versus no-stroke); but a decrease in cerebral p o2 in treated (-11% ± 19%; P = .0048) and untreated (-12% ± 15%; P = .0003) hypertensive rats. Sham animals (normotensive and hypertensive) showed similar magnitude and pattern of IOH when induced with GA before and after sham procedure.

CONCLUSIONS

Our findings are the first demonstration that ischemic stroke per se increases the severity of IOH, particularly when combined with a prior history of hypertension; this combination appears to compromise penumbral perfusion.

Near-Infrared Spectroscopy-Guided, Individualized Arterial Blood Pressure Management for Carotid Endarterectomy under General Anesthesia: A Randomized, Controlled Trial

Background: Differences in blood pressure can influence the risk of brain ischemia, perioperative complications, and postoperative neurocognitive function in patients undergoing carotid endarterectomy (CEA). Methods: In this single-center trial, patients scheduled for CEA under general anesthesia were randomized into an intervention group receiving near-infrared spectroscopy (NIRS)-guided blood pressure management during carotid cross-clamping and a control group receiving standard care. The primary endpoint was postoperative neurocognitive function assessed before surgery, on postoperative days 1 and 7, and eight weeks after surgery. Perioperative complications and cerebral autoregulatory capacity were secondary endpoints. Results: Systolic blood pressure (p < 0.001) and norepinephrine doses (89 (54-122) vs. 147 (116-242) µg; p < 0.001) during carotid cross-clamping were lower in the intervention group. No group differences in postoperative neurocognitive function were observed. The rate of perioperative complications was lower in the intervention group than in the control group (3.3 vs. 26.7%, p = 0.03). The breath-holding index did not differ between groups. Conclusions: Postoperative neurocognitive function was comparable between CEA patients undergoing general anesthesia in whom arterial blood pressure during carotid cross-clamping was guided using NIRS and subjects receiving standard care. NIRS-guided, individualized arterial blood pressure management resulted in less vasopressor exposition and a lower rate of perioperative complications.

The Influence of Extracerebral Tissue on Continuous Wave Near-Infrared Spectroscopy in Adults: A Systematic Review of In Vivo Studies

Near-infrared spectroscopy (NIRS) is a non-invasive technique for measuring regional tissue haemoglobin (Hb) concentrations and oxygen saturation (rSO₂). It may be used to monitor cerebral perfusion and oxygenation in patients at risk of cerebral ischemia or hypoxia, for example, during cardiothoracic or carotid surgery. However, extracerebral tissue (mainly scalp and skull tissue) influences NIRS measurements, and the extent of this influence is not clear. Thus, before more widespread use of NIRS as an intraoperative monitoring modality is warranted, this issue needs to be better understood. We therefore conducted a systematic review of published in vivo studies of the influence of extracerebral tissue on NIRS measurements in the adult population. Studies that used reference techniques for the perfusion of the intra- and extracerebral tissues or that selectively altered the intra- or extracerebral perfusion were included. Thirty-four articles met the inclusion criteria and were of sufficient quality. In 14 articles, Hb concentrations were compared directly with measurements from reference techniques, using correlation coefficients. When the intracerebral perfusion was altered, the correlations between Hb concentrations and intracerebral reference technique measurements ranged between |r| = 0.45-0.88. When the extracerebral perfusion was altered, correlations between Hb concentrations and extracerebral reference technique measurements ranged between |r| = 0.22-0.93. In studies without selective perfusion modification, correlations of Hb with intra- and extracerebral reference technique measurements were generally lower (|r| < 0.52). Five articles studied rSO₂. There were varying correlations of rSO₂ with both intra- and extracerebral reference technique measurements (intracerebral: |r| = 0.18-0.77, extracerebral: |r| = 0.13-0.81). Regarding study quality, details on the domains, participant selection and flow and timing were often unclear. We conclude that extracerebral tissue indeed influences NIRS measurements, although the evidence (i.e., correlation) for this influence varies considerably across the assessed studies. These results are strongly affected by the study protocols and analysis techniques used. Studies employing multiple protocols and reference techniques for both intra- and extracerebral tissues are therefore needed. To quantitatively compare NIRS with intra- and extracerebral reference techniques, we recommend applying a complete regression analysis. The current uncertainty regarding the influence of extracerebral tissue remains a hurdle in the clinical implementation of NIRS for intraoperative monitoring. The protocol was pre-registered in PROSPERO (CRD42020199053).

Comparison of Methods for Monitoring Intra-operative Cerebral Perfusion in Patients Undergoing Carotid Endarterectomy with Selective Shunting: A Systematic Review and Network Meta-Analysis of Randomised Controlled Trials and Cohort Studies

OBJECTIVE

This study aimed to analyse the influence of different methods of monitoring cerebral perfusion (MCP) on stroke, death, and use of intraluminal shunt during carotid endarterectomy (CEA).

METHODS

A systematic review and network meta-analysis was conducted and registered in the PROSPERO registry (CRD42021246360). Medline, Embase, CENTRAL, and Web of Science were searched. Randomised controlled trials (RCTs) and cohort studies with > 50 participants that compared clinical outcomes for different MCP in patients undergoing CEA were included. Papers reporting one or a combination of two of the following MCPs were included in the analysis: awake testing (AT), near infrared spectroscopy (NIRS), electroencephalography (EEG), somatosensory evoked potential (SSEP), motor evoked potential (MEP), transcranial Doppler (TCD), and stump pressure (SP). A random effects network meta-analysis was performed using a binomial likelihood function with a specified logit link for peri-operative stroke or death and shunting as outcomes. Near infrared spectroscopy was excluded due to the lack of studies that could be used for statistical analysis.

RESULTS

Of 1 834 publications, 17 studies (15 cohort studies and two RCTs) including 21 538 participants were incorporated in the quantitative analysis. Electroencephalography was used in the largest number of participants (7 429 participants, six studies), while AT was used in the highest number of studies (10 studies). All monitoring modalities had worse outcomes with respect to stroke or death when compared with AT, with ORs ranging between 1.3 (95% credible interval [CrI] 0.2 - 10.9) for SSEP + MEP and 3.1 (CrI 0.3 - 35.0) for patients monitored with a combination of EEG and TCD. However, the wide CrI indicated that there is no statistically significant difference between the monitoring methods. Patients monitored with a combination of EEG and TCD had the lowest odds of being shunted, while SP had the highest odds of being shunted, also with no statistically significant difference.

CONCLUSION

There is a lack of high quality data on this topic in the literature. The present study showed no significant difference between monitoring methods investigated in the network meta-analysis.