Monitoring: Equipment and Computers
Background and Goal of study: Cerebral oximetry is a simple method of measuring regional cerebral oxygen saturation (SrO2) (1). During carotid endarterectomy (CEA), carotid clamping causes a decrease in the ipsilateral SrO2 (2). The goal was to study the effect of carotid clamping on SrO2 depending on the grade of stenosis of the contralateral carotid artery.
Materials and methods: We studied 27 patients who underwent CEA under general anaesthesia. Patients were divided into two groups: contralateral carotid stenosis of less than 70% (G I), and more than 70%, severe stenosis or occlusion (G II). The INVOS- 4100 cerebral oximeter was used for measure SrO2 at several times: baseline (t1), after induction of general anaesthesia (t2), before carotid clamping (t3), one and five minutes after clamping (t4 and t5), and after declamping (t6). At the same times, direct median arterial pressure (MAP), end-tidal carbon dioxide (PetCO2), pulse oximetry (SpO2) and entropy were recorded. We used for analysis ANOVA test.
Results: In both groups, induction of anaesthesia (t2 vs t1) caused no changes in SrO2. Carotid clamping (t4 vs t3) induced a significant fall in the ipsilateral SrO2 from 61.4% to 57.4%, mean difference: 4.07 CI (1.24-6.91) and on declamping (t6 vs t5) ipsilateral SrO2 raised from 57.78% to 62.48%, mean difference: 4.70 CI (1.45-7.96); there were no significant changes in the contralateral SrO2 at the same times.
No correlation was found between the changes in SrCO2 and the severety of the stenosis.
Conclusions: During CEA, clamping of the carotid artery results in a significative drop of the ipsilateral SrO2, that recovers after declamping. In our study there were no significant differences in SrO2 in patients with contralateral severe stenosis or carotid oclusion compared to patients with a lesser degree of stenosis.
1 Satwant K. Samra, Anesthesiology 2000; 93: 964-970.
2 Cuadra S.A, Vasc Endovascular Surg. 2003 Nov-Dec; 37(6): 407-13.