Pressure measurements as predictors for peroperative neurologic deficits in carotid surgery

Forty-eight carotid endarterectomies were performed using local anaesthesia. The need for an intra-operative shunt was estimated from the development of neurological symptoms during a test clamping period of 1 min. Two patients developed symptoms during test clamping but four others developed symptoms after 11 to 20 min of clamping. The internal carotid back pressure was 30 to 40 mmHg in all these cases and significantly lower than among patients not developing symptoms. A better prediction of the need for a shunt was developed from a combination of the stump index (SI = internal carotid artery stump pressure/systemic pressure x 100) and the carotid index (CI = carotid pressure before clamping/systemic pressure x 100). The combination of SI less than 30 and CI greater than 85 predicted in a highly significant way the need for a shunt during operation. With this method a group of patients with a higher risk of postoperative stroke may also be detected.