Prediction of cerebral ischemic tolerance during carotid cross-clamping by angiographic criteria

Objective. To evaluate the prognostic value of angiographic criteria and internal carotid artery (ICA) stump pressure for shunt placement in carotid surgery under local anaesthesia. Design. Prospective clinical trial at a university hospital. Materials and methods. In 120 patients a cerebral angiography was initiated before undergoing carotid surgery. Seventy-five percent of the patients were neurologically asymptomatic, 13% had transient ischaemic attacks and 12% suffered from previous strokes. The operation was exclusively performed under local anaesthesia and prior to cross-clamping the ICA stump-pressure was measured. A shunt was inserted only if hemispheric symptoms or unconsciousness occurred independent of the angiographic findings or stump pressure. Results. In 23% (27/120) a shunt became necessary and significantly (p < 0.001) more often when there was a cross-flow towards the contralateral hemisphere (12/20 = 60%) or if the contralateral ICA was occluded (9/13=69%). The sensitivity for not needing a shunt in case of cross-flow towards the side of operation was 91% (52/57) whereas the specificity was 35% (22/63). ICA stump-pressure was significantly reduced in patients requiring a shunt (31 mmHg) compared to those not needing a shunt (53 mmHg) (p < 0.001), but no definitive threshold value was found determining the need for shunting. Intraoperatively, no persistent neurological complication developed. Conclusions. Angiographic cross-flow was a good, but not perfect predictor for the need of an intraoperative shunt.