Near Infrared Spectroscopy as a Predictor for Shunt Requirement During Carotid Endarterectomy.

Abstract

Near infrared spectroscopy (NIRS) continuously monitors regional cerebral oxygenation (rSO₂) in the frontal lobes. This method may be used in patients during carotid endarterectomy to indicate the need for shunting. The aim of the study was to evaluate the value of NIRS in determining the need for selective shunting during CEA. A secondary aim was to compare NIRS with stump pressure. Between January 2013 and October 2016, 185 patients from two vascular units, undergoing CEA under local anaesthesia were prospectively included. All patients gave informed consent to participate; there were no exclusion criteria. A Foresight® oximeter was used for rSO₂ measurement, which was compared with stump pressure. Receiver operating characteristic curve analysis was used to identify optimal cutoff points, and sensitivity, specificity, and positive and negative predictive values were calculated. Twenty patients (10.8%) developed neurological symptoms during clamping. Mean stump pressure was lower in the group that developed neurological symptoms than in the group who did not (34 ± 19 mmHg vs. 55 ± 17 mmHg [p < . 01]). Corresponding NIRS results for the decrease in rSO₂ on the ipsilateral side was 15 ± 7% versus 4 ± 6% (p < .01). Using stump pressure ≤50 mmHg as cutoff value for predicting symptoms, the sensitivity was 85% (95% confidence interval [CI] 64-95) and specificity 54% (95% CI 46-61). With a relative decrease in NIRS saturation (ΔrSO₂) of 9%, sensitivity was 95% (95% CI 76-99), and specificity 81% (95% CI 74-86) to predict ischaemic symptoms during carotid clamping. Neurological deterioration during carotid clamping was detected in one patient with a relative decrease in rSO₂ of <9% compared with three patients with a stump pressure >50 mmHg. NIRS allows continuous non-invasive monitoring of cerebral oxygenation during CEA, with high sensitivity and acceptable specificity in predicting cerebral ischaemia and the need for shunting, which makes it an attractive alternative to stump pressure.