Current status of brain monitoring during carotid endarterectomy

Objective

This narrative review aims to analyze the role and efficacy of different methods of intraoperative neuro-monitoring during carotid endarterectomy.

Methods

Articles were collected from online databases, searching ‘carotid endarterectomy,’ intraoperative neuro monitoring,’ and ‘intraoperative neurological monitoring,” from 1999 to 2023.

Results

The search for an optimal intraoperative neuromonitoring technique during carotid endarterectomy is complex and still debated. Regional anesthesia, specifically ultrasound-guided cervical blocks, has become increasingly popular due to its ability to examine the awake patient. Additionally, reports suggest that regional anesthesia leads to shorter operative times, shorter postoperative stays, and less need for shunting. The primary limitations are patient compliance, particularly in cases of claustrophobia, and complications that make it difficult to access the patient’s airway. Currently, there is no definitive evidence favoring one anesthetic technique over another. Other monitoring techniques, such as electroencephalogram, cannot detect ischemia in the subcortical lobe or silent brain strokes caused by micro-embolisms. Although bispectral index is a potential tool, it may lead to false positives due to impaired cerebral perfusion during clamping. Stump pressure measurement is a direct indicator of perfusion pressure across the circle of Willis. However, the critical threshold of “adequate” perfusion is still debated. Near-infrared spectroscopy (NIRS) is a user-friendly, low-cost, noninvasive, and portable method with easily interpretable results. The critical cutoff to detect cerebral ischemia differs among market available NIRS devices; despite high negative predictive value, NIRS is still affected by a low positive predictive value. The available data on the use of routine shunting from randomized controlled trials is limited, and further studies are warranted.

Conclusions

Currently available intraoperative neuro-monitoring techniques for patients undergoing carotid endarterectomy have different uses and limitations, and a conclusive judgement cannot be reached. Future randomized studies and large real-world registries might shed light on this debated topic.