Ischemic Postconditioning in Carotid Surgery

Eversion carotid endarterectomy (eCEA) has proven effective in preventing ischemic brain damage resulting from atherosclerotic disease in the extracranial segment of the carotid arteries. Over time, advancements in surgical techniques have led to a reduction in the incidence of perioperative stroke. To better understand the concept of stroke complications following CEA, a clear distinction between intraprocedural and postprocedural strokes is necessary. Periprocedural strokes are attributed to hypoperfusion or embolization from the site of endarterectomy, while defined causes of postprocedural strokes include local carotid artery thrombosis or cerebral hyperperfusion syndrome (CHS).

CHS, occurring in 1-3% of cases, is a potentially catastrophic event following eCEA, primarily resulting from impaired autoregulation mechanisms and post-revascularization changes in cerebral hemodynamics. Patients with significant carotid stenosis are particularly vulnerable to CHS due to prolonged cerebral hypoperfusion, where collateral circulation serves as a protective mechanism. Another pathway leading to CHS involves increased free radical concentrations, damaging the blood-brain barrier. Identified risk factors for CHS development include advanced age, prior ischemic cerebrovascular events, and contralateral stenosis > 70%.

Various methods for predicting CHS development and collateral circulation insufficiency include cerebral oximetry, transcranial Doppler sonography, perfusion computed tomography, and quantitative magnetic resonance imaging. Cerebral oximetry, with real-time detection of cerebral oxygenated hemoglobin saturation, exhibits promising sensitivity and specificity in predicting CHS occurrence.

Analyzing changes in biomarkers of neuronal ischemic injury and blood-brain barrier integrity offers insight into CHS pathophysiology and indirectly assesses the safety and efficacy of ischemic postconditioning of the carotid artery (IPCT) in high-risk patients. IPCT, shown to have a protective effect in animal models, recently demonstrated encouraging results in human trials.

Utilizing intraoperative neuromonitoring with cerebral oximetry and transcranial Doppler enables real-time monitoring of cerebral oxygenated hemoglobin saturation and flow characteristics during and after IPCT, validating its protective effect and safety in high-risk CHS scenarios.