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

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, rSO2) 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 rSO2 in our experience.

We analyzed data of 104 patients submitted to carotid endarterectomy in narcosis for carotid stenosis of 74 +/- 9%. We compared the rSO2 and invasive blood pressure variations before, during and after carotid cross-clamping.

After carotid closure, ipsilateral rSO2 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 rSO2 returned to basal levels after unclamping, whereas blood pressure was lowered significantly (P = 0.001). Plotting rSO2 and blood pressure value, we found a poor relationship (R2 = 0.0003).

During carotid cross-clamping, an excessive rise of blood pressure is not necessary to guarantee safe values of rSO2. 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.