Assessment of cardiac preload by indicator dilution and transoesophageal echocardiography

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.