Uh. Trivedi et al., RELATIVE CHANGES IN CEREBRAL BLOOD-FLOW DURING CARDIAC OPERATIONS USING XE-133 CLEARANCE VERSUS TRANSCRANIAL DOPPLER SONOGRAPHY, The Annals of thoracic surgery, 63(1), 1997, pp. 167-174
Background. Changes in cerebral blood flow (CBF) during cardiac operat
ions have implications in terms of postoperative neurologic and neurop
sychological dysfunction. Current techniques of CBF measurement are cu
mbersome and invasive. Transcranial Doppler sonography offers a noninv
asive means of assessing changes in CBF. The aim of this study was val
idation of this technique with existing methods of CBF measurement dur
ing cardiac operations. Methods. We compared the changes in CBF using
xenon-133 clearance with changes in middle cerebral artery velocity by
transcranial Doppler sonography (V-MCA) using pH-stat and alpha-stat
acid-base management during cardiopulmonary bypass. Measurements were
taken (1) before bypass, (2) at 28 degrees C on bypass, (3) at 37 degr
ees C on bypass, and (4) after bypass. Relative changes in CBF and V-M
CA, calculated as the percent change from the prebypass baseline value
normalized to 100%, were used in this analysis. Results. During the h
ypothermic phase of cardiopulmonary bypass, CBF and V-MCA increased by
45.9% and 51.8%, respectively (p < 0.001), during pH-stat acid-base m
anagement but decreased by only 26.4% and 22.4%, respectively (p < 0.0
001), during alpha-stat acid-base management. Linear regression analys
is of the absolute changes in CBF (mL . 100 g(-1) . min(-1)) and V-MCA
(cm/s) showed a significant correlation (r = 0.60; r(2) = 0.36; p < 0
.0001), but a better correlation was obtained when relative changes in
CBF and V-MCA were compared (r = 0.89; r(2) = 0.79; p < 0.0001). Conc
lusions. Measurements of V-MCA, expressed as relative changes of a pre
-cardiopulmonary bypass level (using the noninvasive transcranial Dopp
ler sonographic technique), can be used to examine CBF changes during
cardiopulmonary bypass. (C) 1997 by The Society of Thoracic Surgeons