Cerebral oximetry index indicates delirium or stroke after carotid endarterectomy: An observational study

Backgrounds

The cerebral oximetry index (CO_x) uses near-infrared spectroscopy to estimate cerebral autoregulation during cardiac surgery. However, the relationship between intraoperative loss of cerebral autoregulation and postoperative delirium or stroke remains unclear in patients recovering from carotid endarterectomy (CEA).

Methods

Our prospective observational cohort study enrolled patients scheduled for CEA. CO_x was estimated as the coefficient of a continuous, moving Spearman correlation between mean arterial pressure and cerebral oxygen saturation. A receiver operating characteristics curve with Youden's index identified the optimal CO_x threshold for predicting a composite of postoperative delirium or new-onset overt stroke.

Results

One hundred and forty patients scheduled for CEA were enrolled. The incidence of delirium was 10.7 % (15/140) and the incidence of stroke was 3.6 % (5/140), including 1 patient who had both. The cumulative anesthesia time when CO_x exceeded 0.3 was longer in patients with complications than those without. When CO_x > 0.6, the corresponding predictive ability was AUC = 0.69, Youden index = 0.61, P = 0.0003, with a positive predictive value of 100 %. In the post hoc subgroup analyses, before clamping, the greatest increase in the risk was observed when CO_x > 0.7 for 20 min (Odds ratio = 3.10, 95 % CI 2.20, 3.78). In contrast, CO_x was not predictive during clamping. After clamping, the optimal CO_x threshold was 0.4 (AUC = 0.85, Youden index = 0.82, P < 0.0001), with the positive predictive value being 100 %.

Conclusions

CO_x is a promising metric for predicting postoperative delirium or new-onset overt stroke in patients having CEA. The optimal CO_x threshold was 0.7 in the pre-clamping phase and 0.4 in the post-clamping phase.