Cerebral oximetry during carotid clamping: is blood pressure raising necessary?

Background Carotid endarterectomy is subject to a significant risk of intraoperative stroke. Anesthetic management of patients must provide optimal monitoring of cerebral blood perfusion to establish whether intraluminal carotid shunting is necessary. Cerebral oximetry (regional cerebral oxygen saturation, rSO(2)) measurement can ascertain whether brain perfusion is adequate. During carotid cross-clamping, a rise of blood pressure may be required to guarantee a collateral blood supply throughout the circle of Willis. We retrospectively evaluated the relationship between blood pressure and rSO(2) in our experience. Methods We analyzed data of 104 patients submitted to carotid endarterectomy in narcosis for carotid stenosis of 74 +/- 9%. We compared the rSO(2) and invasive blood pressure variations before, during and after carotid cross-clamping. Results After carotid closure, ipsilateral rSO(2) was reduced significantly (from 64.8 +/- 8.1% to 60.8 +/- 8.1%; P = 0.0004), while systolic and mean blood pressure rose. The ipsilateral rSO(2) returned to basal levels after unclamping, whereas blood pressure was lowered significantly (P = 0.001). Plotting rSO(2) and blood pressure value, we found a poor relationship (R-2 = 0.0003). Conclusion During carotid cross-clamping, an excessive rise of blood pressure is not necessary to guarantee safe values of rSO(2). On the contrary, hypertension could expose the patient to risk of cardiac accident. So we have modified our intraoperative strategy avoiding controlled hypertension for normotensive management during carotid clamping. J Cardiovasc Med 11:522-528 (C) 2010 Italian Federation of Cardiology.