Cerebral oxygen saturation and middle cerebral artery flow velocity changes during carotid endarterectomy

Introduction:
Neurological status of the carotid endarterectomy (CEA) patients can be monitored easily during regional anesthesia. The aim of our prospective study was to assess the changes in middle cerebral artery velocity (MCAv) and cerebral O2 saturation(rSO2) in patients with or without neurological symptoms during CEA.

Methods:
106 patients scheduled for CEA under LA (local anesthesia) were included for monitoring, among them bilateral transcranial Doppler (TCD) sonography was performed in 44 patients. We recorded all data at 8 stages of surgery: before regional block, after completing regional block, before clamp, after clamp, 5 minutes after clamp, 10 minutes after clamp, declamp, post operatively.

Results:
In the total cohort, rSO2, the MCAv and the pulsatility index (PI) significantly decreased during clamping on the affected site, and decreased compared to the non-affected side too. The higher change was observed in the MCAv . After declamping we found a significant increase in MCAv (+30%) and rSO2 (+18,3%), that continued during the postoperative period.
In patients with intraoperative neurological symptoms:
-rSO2 significantly decreased in the affected side compared to the non-affected side, a 24% decrease after clamp was observed in the affected side (compared to 14% decrease in the group without symptoms)
-MCAv significantly decreased after clamp in the affected side (75% compared to 47% decrease in the group without symptoms)

Discussion:
The clamping of the internal carotid artery significantly decreases both rSO2 and MCAv in the affected side. Decreasing in percent is higher in the MCAv than in the rSO2. We found a significantly higher decrease in rSO2 (24% / 14%) and MCAv (75% / 47%) in patients with intraoperative neurological symptoms. The significant decrease of the pulsatility index during clamp time in the affected side indicates dilatation of the resistance arterioles.

References:

Pennekamp CW: Eur J Vasc Endovasc Surg. 2013;46(4):397-403.
Pennekamp CW: Cerebrovasc Dis. 2012;34(4):314-21.