Intrathoracic blood volume index measured by thermodilution for preload monitoring after cardiac surgery

Objective: To investigate the accuracy of measurement of intrathoracic blood volume index by single thermodilution (ITBVI*) and its sensitivity to detect changes in preload after cardiac surgery compared with conventional transpulmonary arterial dye dilution ITBVI and with conventional monitoring (central venous pressure [CVP] and left ventricular end-diastolic area index [EDAI] by transesophageal echocardiography).

Design: Prospective clinical study.

Setting: University hospital.

Participants: Nineteen patients immediately after cardiac surgery.

Interventions: Volume loading was administered with 20 mL of oxypoligelatine (Haemaccel [Behringwerke Aktiengesellschaft Corp, Marburg, Germany]) 3.5% times body mass index over 10 minutes.

Measurements and main results: Intrathoracic blood volume index was measured by dye dilution (ITBVI) and thermodilution (ITBVI*) immediately before and after volume loading. Measurements of ITBVI and ITBVI* correlated closely (r = 0.94; p < 0.0001). With volume loading, ITBVI and ITBVI* increased significantly from 877 +/- 195 mL/m(2) to 967 +/- 180 mL/m(2) and from 889 +/- 195 mL/m(2) to 954 +/- 185 mL/m(2). Percent changes in ITBVI (deltaITBVI) and ITBVI* (deltaITBVI*) did not differ significantly and correlated closely (r = 0.90; p < 0.0001). Percent changes in cardiac index (CI) as a result of volume loading (deltaCI) revealed significant correlation to deltaITBVI (r = 0.85; p < 0.0001) and to deltaITBVI* (r = 0.76; p < 0.0005). No significant correlation could be found between deltaCI and deltaEDAI or deltaCVP.

Conclusion: In patients undergoing cardiac surgery, determination of ITBVI* revealed close agreement with measurements derived by ITBVI. Enhancement in cardiac preload was adequately detected by ITBVI*.