The prognostic value of cerebral oxygenation and retrograde pressure during carotid endarterectomy

Aim: The study aimed to determine the predictive value of retrograde pressure (RP) indicators and cerebral oxygenation in the evaluation of ischemic brain damage during carotid endarterectomy (CEA). Methods: This nonrandomized, prospective pilot study included 87 patients with asymptomatic stenosis greater than 70% who underwent carotid endarterectomy under general anesthesia. Brain tolerance to ischemia was determined by measuring and evaluating RP (ΔrSO2) and cerebral oxygenation (rSO2) during a trial clamping of the carotid artery. Depending on the degree of reduction of cerebral oxygenation from the baseline (ΔrSO2) during a trial clamping of the carotid artery, patients were divided into 3 groups: the first group (n = 35) - ΔrSO2 2 from 10 to 19.9%, the third group (n = 14) - ΔrSO2 ≥ 20%. The primary end-point of the study was to obtain the AUC value exceeding 0.70, which could mean a high predictive quality of research methods. Results: There were no perioperative strokes or myocardial infarctions during the study. Average time of carotid artery clamping was 28 (26-30) minutes. 3 patients who received temporary shunts were excluded from the study because of a simultaneous decrease in the rSO2 and ΔrSO2 indicators. It was found out that S-100 and NSE protein concentration in all groups did not significantly differ at different stages (p> 0.05). A temporary shutdown of blood flow in the carotid artery during CEA is accompanied by significant elevation of cerebral damage markers (S-100, NSE) concentration with their subsequent restoration at 3 days after surgery. ROC - analysis revealed that none of the methods for assessing cerebral ischemic tolerance (RP, ΔrSO2 and rSO2) is precise enough (AUC > 0.7) to predict brain injury during carotid endarterectomy. Satisfactory, but a poor quality (AUC2 and rSO2) did not exceed the area under the curve (AUC) over 0.60. Conclusion: Methods of measuring retrograde pressure and cerebral oxygenation are merely a reflection of the collateral blood flow and the cerebral oxygenation level due to their close relationship, but they cannot be used as predictors of ischemic neuronal damage during carotid endarterectomy because of poor predictive quality.