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KMID : 0356919940270101378
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Korean Journal of Anesthesiology
1994 Volume.27 No. 10 p.1378 ~ p.1385
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Transcranial Doppler Study in Carbon Dioxide Reacitivity of Middle Cerebral Blood Flow Velocity During Hypotermic Nonpulsatile Cardiopulmonary Bypass
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Abstract
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The recording of middle cerebral artery (MCA) flow velocity by transcranial Doppler technique offers a new, noninvasive, and continuous technique for studies of cerebral circulation. The influence of changes in PaCO2 on MCA flow velocity were
observed
during hypothermic cardiopulmonary bypass(CPB) surgery by means of transcranial Doppler techniques.
In ten patients who were undergoing hypothermic CPB surgery, the right MCA flow velocity was measured before initiation of CPB(prebypass period) and after the termination of CPB (postbypass period). During steady-state CPB(constant hematocrit,
constant
temperature, and constant total pump flow), baseline MCA flow velocity(CPB I period) was measured and then repeated after specific alteration of PaCO2 achieved by changing of fresh gas flow to oxygenators (CPB II period). And carbon dioxide
reactivity
defined as percent change of MCA flow velocity per mmHg changes in PaCO2 was observed during stable hypothermic CPB.
MCA flow veocity showed no statistical difference between the prebypass value(56.9 13.5cm/sec)and the postbypass value(64.7±29.7 cm/sec). PaCO2 of 20.5±2.5 mmHg was associated with MCA flow velocity of 25.2±10.1 cm/sec in the CPB I period
while
PaCO2
of 27.1±3.5 mmHg was associated with MCA flow velocity of 35.3±12.9 cm/sec. MCA flow velocity carbon dioxide reactivity during steady-state hypothermic CPB was 6.68±2.26 %/mmHg.
These results have demonstrated that the response of MCA flow velocity to changes in PaCO2 was well maintained during hypothermic CPB and the use of transcranial Doppler would give valuable results in the study of cerebral circulation during
hypothermic
CPB.
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