Increased Oxygen Administration Improves Cerebral Oxygenation in Patients Undergoing Awake Carotid Surgery

BACKGROUND: During regional anesthesia for carotid endarterectomy (CEA), 10% to 15% of patients develop signs of cerebral hypoxia after cross-clamping, manifested as changes in speech, cerebration or contralateral motor power. Reversal of such neurological deficits using administration of 100% O(2) has been described. We used near-infrared cerebral oximetry to assess whether 100% O(2) reliably improves regional cerebral oxygenation (rSO(2)) during carotid cross-clamping. METHODS: Sixteen patients undergoing awake CEA were studied. Bilateral rSO(2) optodes were applied before the initiation of sedation and the conduct of the regional blockade. Patients received 28% oxygen by Venturi facemask. Perioperative blood pressure was maintained at or within 10% above the patient's normal limits during carotid cross-clamping. After cross-clamping, 100% O(2) was administered for 5 min by a close-fitting anesthetic facemask. The O(2) mask was then removed and the patient breathed room air. The effects on rSO(2) readings and arterial blood gases were observed after each intervention. RESULTS: Data were analyzed for 15 patients. Ipsilateral rSO(2) values decreased by 7.4% 5% after carotid cross-clamping. Administration of 100% 0, resulted in an increase in ipsilateral rSO(2) in all patients of 6.9% +/- 3.3% (range, 1%-12%) (paired t-test, P < 0.001) over the cross-clamped value while receiving 28% O(2). Hemodynamic variables and arterial Paco(2) values were unaltered. CONCLUSION: With the carotid cross-clamped, ipsilateral rSO(2) was reliably increased by the administration of 100% O(2) compared with 28% O(2). The etiology of this increase is unclear, but may relate to the associated increase in O(2) content of the blood or to an improvement in cerebral blood flow. Thus administration of 100% O(2) during carotid cross-clamping may be beneficial for all patients undergoing CEA.