ASSESSMENT OF HEMODYNAMICS (see
also Chapter 18
and Chapter
32
)
Preload
Quantitative TEE measurements of ventricular preload reflect changes
in ventricular diastolic volume more accurately than do data obtained from the pulmonary
artery catheter.[36]
[37]
[38]
[39]
For instance,
in 30 patients scheduled for cardiac surgery, Cheung and colleagues removed 15% of
each patient's blood volume (in six equal aliquots) before cardiopulmonary bypass
while monitoring their TG mid SAX cross section with TEE.[40]
A significant decrease in LV end-diastolic area was detected after removal of the
first aliquot (2.5% of the estimated blood volume or about 200 mL). With subsequent
aliquots, end-diastolic area decreased linearly (0.3 cm2
/1.0% of blood
volume removed) such that after removal of all six aliquots, the end-diastolic area
had decreased by 27% in patients with normal LV function and by 21% in patients with
depressed LV function. Although pulmonary artery occlusion pressure and central
venous pressure also declined during the study, their correlation with end-diastolic
area and blood removal was very weak or nonexistent. In a different study, TEE Doppler
estimates of transmitral flow provided a better method to predict cardiac output
response to rapid intravenous fluid administration than did pulmonary artery occlusion
pressure or LV end-diastolic area.[41]
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