December 22, 2008

CEREBRAL OXIMETRY CAN REPLACE CAROTID ARTERY STUMP PRESSURE MEASUREMENTS DURING ENDARTERECTOMY

Jee Yeun Lee, GEORGE HINES, MARTIN FEUERMAN, ALEXANDRA OLESKE, REESE WAIN.
WINTHROP UNIVERSITY HOSPITAL, MINEOLA, NY, USA.

OBJECTIVE: Carotid artery stump pressures (CASP) obtained immediately following carotid clamping have been used extensively during carotid endarterectomy (CEA) to predict cerebral perfusion and the need for a shunt. Cerebral oximetry is a simple, non invasive, and continuous method for monitoring regional cerebral oxygen saturation (rSO₂) whose use in this regard has not been validated. We sought a correlation between cerebral oximetry values and CASP in patients undergoing CEA.
METHODS: The FORE-SIGHT absolute cerebral oximeter was used to evaluate rSO₂ before (t0) and 30-60 seconds after (t1) clamping the common (CCA) and external (ECA) carotid arteries. CASP was measured and correlated with changes in rSO₂ (t0-t1).
RESULTS: 39 CEA’s in 38 patients were performed under general anesthesia. Clamping of the CCA and ECA resulted in a significant decrease in rSO₂ (t0-t1) of 4.74 ± 3.75 units or a percent difference of 6.99 ± 5.57%. When analyzed via Spearman’s correlation, CASP measurements correlated closely and significantly (p= -0.52) with changes in rSO₂. (Table ) A larger drop in rSO₂ correlated with a lower CASP. Based on regression analysis, stump pressures of 50 & 25 mmHg were predicted by changes of rSO₂ of 3.76 units and 19 units or 5.59% and 27.4% respectively.

Regression analysis of mean stump pressure and absolute difference of cerebral oximetry
CONCLUSION: Cerebral oximetry can serve as a simple and non invasive alternative to CASP for evaluating cerebral perfusion following carotid cross clamping. The ability to continuously measure changes in cerebral oxygen saturation via oximetry may be an important advance over the one time CASP measurement in predicting the need for shunting throughout the entire CEA.

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