Background and objective Assessment of cardiac preload is of major importance in the management of critically ill patients. Echocardiographic determined left ventricular end-diastolic area and indicator dilution derived intrathoracic blood volume are used as surrogates for cardiac preload. However, no controlled comparison studies on the relationship between induced changes in end-diastolic area and intrathoracic blood volume and concomitant changes in stroke volume index are available.
Methods The effects of a change in body position on these variables were investigated in 10 anaesthetized patients.
Results Intrathoracic blood volume and end-diastolic area decreased by 18 ± 11% and 27 ± 13% respectively. Stroke volume index concomitantly decreased by 19 ± 11%. Correlation analysis revealed a close relation between stroke volume index and intrathoracic blood volume (r = 0.75) and end-diastolic area (r = 0.76).
Conclusions Within the observed range of data, intrathoracic blood volume and end-diastolic area are equivalent indices of cardiac preload.