Regional cerebral blood flow during rewarming of cardiopulmonary bypass correlates with posthypothermic regional glucose use.
OBJECTIVE
Although global measurements of cerebral blood flow and metabolism during and after profoundly hypothermic cardiopulmonary bypass have been performed both in experimental animals and in human beings, little is known about their regional changes. The purpose of this study was to investigate the changes in regional cerebral blood flow during profoundly hypothermic cardiopulmonary bypass and regional cerebral glucose use after cardiopulmonary bypass.


METHODS
We measured regional cerebral blood flow with positron emission tomography during both the cooling (n=5) and rewarming (n=5) of hypothermic cardiopulmonary bypass in anesthetized dogs by continuously infusing 15O-labeled water. We altered the core temperature between 20 degrees and 37 degrees C. To assess the integrity of brain metabolism, we measured the regional cerebral glucose use by bolus injections of 18F-labeled 2-fluoro-2-deoxy-D-glucose.


RESULTS
Regional cerebral blood flow decreased homogeneously during cooling. The regional cerebral blood flow at 20 degrees C was about one fourth of that at 37 degrees C. In contrast, at 24 degrees, 28 degrees , and 32 degrees C during rewarming, there were significant interregional differences in the regional cerebral blood flow for given temperatures (p=0.0075, 0.034, and 0.048, respectively). These interregional differences disappeared after rewarming. Although the regional cerebral blood flow significantly correlated with the regional cerebral glucose use in the control condition at 37 degrees C without cardiopulmonary bypass (r=0.75; p=0.00012), this correlation disappeared after profoundly hypothermic cardiopulmonary bypass (r=0.204; p=0.388). Regional cerebral blood flow at 32 degrees C during rewarming positively correlated with the regional cerebral glucose use after cardiopulmonary bypass (r=0.655; p=0.0017).


CONCLUSIONS
The altered regional cerebral blood flow during rewarming of profoundly hypothermic cardiopulmonary bypass might affect regional brain metabolism.
Miyano
H
H
Department of Cardiovascular Dynamics, National Cardiovascular Center Research Institute, Suita, Osaka, Japan.
Inagaki
M
M
Hashimoto
N
N
Shishido
T
T
Kawada
T
T
Miyake
Y
Y
Sunagawa
K
K
D000818:Animals; D001921:Brain / Q000000981:diagnostic imaging / Q000378:metabolism*; D002315:Cardiopulmonary Bypass; D002560:Cerebrovascular Circulation / Q000502:physiology*; D004285:Dogs; D005462:Fluorine Radioisotopes; D019788:Fluorodeoxyglucose F18; D007036:Hypothermia, Induced; D019275:Radiopharmaceuticals; D017694:Rewarming; D014055:Tomography, Emission-Computed
D005462:Fluorine Radioisotopes; D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18