This randomized controlled study compares two methods of intraoperative cerebral ischemia monitoring during carotid endarterectomy performed under regional anesthesia: neurological testing in the awake patient and near-infrared spectroscopy (NIRS). The study aims to determine whether NIRS is equivalent to awake neurological testing in detecting cerebral ischemia during carotid artery clamping and in guiding the use of an intraluminal shunt.

Cerebral ischemia during carotid endarterectomy (CEA) remains one of the most important causes of perioperative neurological morbidity and mortality. During carotid artery clamping, cerebral perfusion depends on the adequacy of collateral circulation, most importantly through the Circle of Willis. Inadequate collateral flow may lead to hypoperfusion, resulting in transient or permanent ischemic brain injury. For this reason, intraoperative cerebral monitoring is widely used to identify patients who require placement of an intraluminal shunt during carotid cross-clamping in order to maintain adequate cerebral blood flow.

In patients undergoing CEA under regional anesthesia, awake neurological testing is considered a reliable method for detecting cerebral hypoperfusion. By continuously assessing verbal communication and contralateral hand motor function, the surgical team can identify early neurological deterioration indicating cerebral ischemia. However, this approach is operator-dependent, subjective, and cannot provide continuous quantitative data on cerebral perfusion. In addition, subtle or subclinical ischemic events may go undetected by neurological testing alone.

Near-infrared spectroscopy (NIRS) is a non-invasive monitoring technique that measures regional cerebral oxygen saturation and reflects changes in cerebral perfusion. NIRS provides continuous, real-time, and objective assessment of cerebral oxygenation during surgery. A decrease in NIRS values during carotid artery clamping has been associated with cerebral hypoperfusion and may indicate a need for shunt placement. Despite increasing use of NIRS in vascular surgery, its diagnostic accuracy and equivalence to awake neurological testing for detection of cerebral ischemia during CEA have not been definitively established.

This prospective randomized controlled trial is designed to compare awake neurological testing and NIRS monitoring for the detection of intraoperative cerebral ischemia during carotid endarterectomy. The study will be conducted at the Clinic for Vascular and Endovascular Surgery, University Clinical Center of Serbia, between January 1, 2026 and January 1, 2028. Adult patients with symptomatic or asymptomatic carotid artery stenosis who meet criteria for surgical treatment will be eligible for inclusion. The indication for carotid endarterectomy will be established based on duplex ultrasonography and multislice computed tomography (CT) angiography of the carotid and cerebral vessels.

After providing written informed consent, patients will be randomized electronically in a 1:1 ratio into two groups. In both groups, carotid endarterectomy will be performed under cervical block anesthesia, allowing continuous neurological assessment. Near-infrared spectroscopy will be recorded in all patients; however, the decision to insert an intraluminal shunt will be guided by the randomized monitoring method.

In the Awake Neurological Testing group (TUBS), shunt placement will be based on the occurrence of neurological deficits during carotid cross-clamping, including impaired verbal communication or decreased motor function of the contralateral hand. In the NIRS group, shunt placement will be based on a decrease of more than 20% from baseline in regional cerebral oxygen saturation measured by near-infrared spectroscopy.

Preoperative evaluation will include duplex ultrasound of the carotid arteries, CT angiography, detailed physical and neurological examination by a neurologist, and magnetic resonance imaging (MRI) of the brain. Postoperative brain MRI will be performed within 7 days after surgery to detect both clinically apparent ischemic events and silent ischemic brain lesions (new ischemic brain MRI lesions). These silent lesions are considered important markers of perioperative cerebral ischemia and may have prognostic significance.

The primary outcome of the study is the rate of intraoperative cerebral ischemia, defined as the need for intraluminal shunt placement during carotid artery clamping based on the assigned monitoring method. Secondary outcomes include postoperative neurological deficits, ischemic stroke, transient ischemic attack, all-cause mortality, and the occurrence of new ischemic brain lesions on postoperative MRI. In addition, the agreement between awake neurological testing and NIRS monitoring will be evaluated using kappa statistics, and the optimal NIRS threshold associated with ischemic brain injury will be determined.

A total of 160 patients (80 in each group) will be enrolled. This sample size is based on calculations for diagnostic accuracy and agreement between methods, assuming a sensitivity of 75%, specificity of 85%, a kappa value of 0.35, a power of 80%, and a type I error rate of 5%. Statistical analysis will include descriptive and inferential methods, including parametric and non-parametric tests, as well as univariate and multivariate models to identify factors influencing the sensitivity and specificity of both monitoring strategies. Analyses will be performed using both per-protocol and intention-to-treat approaches.

This study aims to determine whether near-infrared spectroscopy provides a reliable and clinically equivalent alternative to awake neurological testing for intraoperative cerebral ischemia monitoring and shunt decision-making during carotid endarterectomy.

Inclusion Criteria:

• Patients with asymptomatic and symptomatic narrowing of the carotid artery in whom operative treatment is indicated, diagnosed by initial Duplex ultrasonographic examination or CT angiography.
• Written consent of the patient to participate in the study

Exclusion Criteria:

• - previous hemorrhagic stroke
• non-atherosclerotic carotid disease
• significant atherosclerotic changes in the aortic arch
• hypercoagulable and conditions with embologenic potential (congenital or acquired thrombophilia, malignant disease, atrial fibrillation, significant heart failure and valvular disease)