Cross-flow determination by transcranial Doppler predicts clamping ischemia in patients undergoing carotid endarterectomy.

Aim of the paper was to assess the reliability of preoperative cross-flow determination by transcranial Doppler measurement (TCD) to detect clamping ischemia in patients undergoing carotid endarterectomy with selective shunting. Retrospective one-to-one matched-pair analysis of 72 patients undergoing carotid endarterectomy with preoperative TCD scanning. Matching criteria were gender, degree of contralateral stenosis and the type of stenosis (asymptomatic or symptomatic). Patients in need for a secondary shunt insertion had significantly less cross-flow in preoperative TCD measurement (N.=14; 38.89%) compared to the control group (N.=32; 88.89%: P=0.0001%). The sensitivity of the cross-flow determination to predict clamping ischemia was 88.9%, the specificity 61.1%. The risk of developing a clamping ischemia in the absence of a cross-flow was 12 fold higher (OR: 12.6; 95% CI: 3.7-43.3). The existence of circulatory impairment of the MCA was associated with the presence of a collateral flow in the ACoA (OR 3.21; P=0.0531; likelihood ratio test 0.0481). Other factors like renal insufficiency, the degree of stenosis or the stump pressure showed no association with a cross-flow of the ACoA in a multivariate model. TCD scanning is highly reliable to detect cross-flow prior to carotid surgery and thus helpful to identify patients at risk for clamping ischemia and need for shunting.