Good correlation between cerebral oxygenation measured using near infrared spectroscopy and stump pressure during carotid clamping

Abstract

Aim: Intraoperative hypoperfusion ischemia is one factor that leads to perioperative stroke during carotid endarterectomy. Selective shunting is one way to reduce intraoperative hypoperfusion, but to shunt selectively needs a sensitive and simple monitoring system together with the rules for insertion. Near infrared spectroscopy (NIRS) is a monitoring system that can be used throughout the operation, and reflects the cerebral oxygenation instantly, but its value in insertion of shunt tubes is still controversial. The aim of this study was to determine criteria that can be used to insert shunt tubes.

Methods: Forty-three consecutive patients with severe carotid stenosis undergoing carotid artery surgery with NIRS monitoring were enrolled in the study. Under general anesthesia, the optodes of NIRS were placed bilaterally on the forehead. Throughout the operation, regional saturation of the frontal lobe (SdO2) was monitored every 5 s.

Results: All operations were performed without any perioperative deaths. NIRS showed that SdO2 fell rapidly as soon as the artery was cross-clamped, and reached the lowest level after 60 s. SdO2 change at 60 s and the stump pressure showed good correlation (r=0.65), and stump pressure of 40 mmHg was almost equivalent to 5% SdO2 decrease in NIRS.

Conclusion: NIRS monitoring is suitable for monitoring during carotid endarterectomy for selective shunting, because it can be used throughout the operation and shows the immediate change in oxygenation. There is a possibility that a decrease of 5% can be used as a decisive value for shunt insertion.