Key result
Transcranial Doppler sonography measurement of middle cerebral artery velocity correlated poorly (r=0.33) with actual cerebral blood flow during hypothermic cardiopulmonary bypass.
Why the study?
Does middle cerebral artery velocity measured by Transcranial Doppler correlate with actual cerebral blood flow during hypothermic cardiopulmonary bypass in adults?
Observational (n=16)
Does middle cerebral artery velocity measured by Transcranial Doppler correlate with actual cerebral blood flow during hypothermic cardiopulmonary bypass in adults?
Effect estimate: r = 0.33
Transcranial Doppler sonography may be of limited usefulness for assessing cerebral blood flow during hypothermic, nonpulsatile cardiopulmonary bypass due to poor correlation with actual cerebral blood flow.
TCD MCA velocity correlation with CBF during CPB remains uncertain; leaves open validation before guiding cerebral perfusion.
A noninvasive, simple, and continuous method to assess cerebral perfusion during cardiopulmonary bypass (CPB) could help prevent cerebral ischemia.Transcranial Doppler sonography (TCD) allows a noninvasive, on-line measurement of blood flow velocity in cerebral arteries. The correlation of TCD-estimated and actual cerebral blood flow (CBF) has not been well studied during CPB. We determined the correlation of middle cerebral artery (MCA) mean velocity and CBF determined by the Kety-Schmidt method during nonbypass and two hypothermic bypass flow conditions. Sixteen patients undergoing hypothermic (27 degrees C) CPB for coronary artery bypass grafting and/or valve replacement surgery were enrolled in the study. We were able to determine MCA velocity in only 12 patients. We determined CBF and MCA velocity in each patient during four 15-min study periods: 1) prebypass after sternotomy before aortic cannulation; 2) hypothermic (27 degrees C) CPB with 1.2 L centered dot min-1 centered dot m-2 pump flow; 3) hypothermic CPB with 2.4 L centered dot min-1 centered dot m-2 pump flow, and 4) 30 min after weaning from CPB. There was no difference in the mean arterial pressure between the two CPB pump blood flows. The pooled change in MCA velocity and CBF as percentage of baseline (prebypass) for all patients and at all time points had a correlation of 0.33 (r). A decrease or increase in MCA velocity did not necessarily indicate a corresponding decrease or increase in CBF. This technology may be of limited usefulness during the circulatory condition of hypothermic, nonpulsatile CPB. (Anesth Analg 1996;82:1146-51)
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Nuttall et al. (1996) conducted an observational in Coronary artery bypass grafting and/or valve replacement surgery requiring hypothermic cardiopulmonary bypass (n=16). Transcranial Doppler sonography (TCD) for middle cerebral artery velocity vs. Kety-Schmidt method for cerebral blood flow was evaluated on Correlation between middle cerebral artery mean velocity and cerebral blood flow (r = 0.33). Transcranial Doppler sonography measurement of middle cerebral artery velocity correlated poorly (r=0.33) with actual cerebral blood flow during hypothermic cardiopulmonary bypass.
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