TRANSCRANIAL DOPPLER BLOOD-FLOW VELOCITY VERSUS XE-133 CLEARANCE CEREBRAL BLOOD-FLOW DURING MILD HYPOTHERMIC CARDIOPULMONARY BYPASS

Objective. Transcranial doppler (TCD) is used during cardiopulmonary b ypass (CPB) to assess cerebral emboli and to estimate cerebral perfusi on. We sought to compare TCD middle cerebral artery blood flow velocit y (V-mca) to Xe-133 clearance cerebral blood flow (CBF) measurements d uring mild hypothermic CPB thus determining its utility in cerebral pe rfusion assessment. Methods. Thirty-four patients undergoing mild hypo thermic CPB (35 degrees C) were studied and had comparisons of V-mca a nd Xe-133 CBF at three time intervals, 10, 30 and 60 min after the ins titution of CPB. Linear regression analysis was performed on data from each of the 3 intervals as well as for pooled data from all 3 periods . Results. The correlation coefficients for the 3 time periods were, r = 0.32 (p = 0.12), r = 0.32 (p = 0.11), r = 0.48 (p = 0.02), respecti vely. The pooled data correlation had a coefficient of 0.34 (p = 0.003 ). Conclusion. These findings suggest that TCD V-mca is a relatively p oor correlate of CBF during mild hypothermic CPB.