Efficacy of Continuous Regional Cerebral Oxygen Saturation Monitoring Using INVOS as a Predictor of Cerebral Hyperperfusion Syndrome Following Carotid Endarterectomy: A Case Report

Noninvasive monitoring of regional cerebral oxygen saturation (rSO2) has been introduced in settings for estimation of cerebral perfusion and cerebral blood flow. We predicted the risk of cerebral hyperperfusion syndrome following carotid endarterectomy (CEA) by rSO2 monitoring using INVOS. A 77-year-old woman with asymptomatic right internal carotid artery (ICA) stenosis was admitted to our hospital and underwent CEA with INVOS monitoring. INVOS value was 70 in the right ICA and 66 in the left ICA before ICA clamping, and 59 and 79, respectively, after ICA clamping. Immediately after declamping, INVOS value was 82 in the right and 71 in the left ICA. As increase in the INVOS value of the right ICA suggested cerebral hyperperfusion, blood pressure was controlled strictly under anesthesia with propofol. Mean flow velocity ratio in the middle cerebral artery (MFV ratio) on the day after the operation was 1.81, and SPECT showed cerebral hyperperfusion in the ipsilateral cerebral hemisphere. Continuous monitoring of rSO2 using INVOS enabled estimation of the risk of cerebral hyperperfusion syndrome. MFV ratio decreased to 1.35 five days after surgery, and the patient awakened from anesthesia. This patient was able to avoid the risk of cerebral hyperperfusion syndrome. In conclusion, INVOS was useful for monitoring hyperperfusion syndrome following CEA.