Preload and haemodynamic assessment during liver transplantation: a comparison between the pulmonary artery catheter and transpulmonary indicator dilution techniques.

BACKGROUND AND
OBJECTIVE: Liver transplantation is characterized by several changes in intravascular blood volume due to vasodilatation based on neurohumoral mediators, intraoperative bleeding and anaesthesia technique effects. Today, with the transpulmonary indicator dilution technique, cardiac index (CIart) can be evaluated and preload assessed in terms of the intrathoracic blood volume index (ITBVI). The aim was to analyse in patients undergoing liver transplantation two preload variables, pulmonary artery occlusion pressure (PAOP) and ITBVI with respect to cardiac index (CIpa) and stroke volume index (SVIpa), the correlation between ITBVI and PAOP, and secondary the relationship between the changes (delta) of ITBVI and PAOP and the changes of CIpa and SVIpa, and the relationships between deltaITBVI and deltaPAOP. The reproducibility and precision of all CIart and CIpa measurements were also evaluated.
METHODS: A prospective study was performed in 60 patients monitored with a pulmonary artery catheter and with the PiCCO system. The variables were evaluated with a linear regression model.
RESULTS: Linear regression analysis between ITBVI-CIpa and ITBVI-SVIpa were r2 = 0.47 (P < 0.0001) and r2 = 0.55 (P < 0.0001) respectively, while PAOP poorly correlated to CIpa (r2 = 0.02), SVIpa (r2 = 0.015) and ITBVI (r2 = 0.002). Only changes in ITBVI were correlated with changes in CIpa (delta1, r2 = 0.37; delta2, r2 = 0.32), and SVIpa (delta1, r2 = 0.60; delta2, r2 = 0.47). The mean bias between CIart and CIpa was 0.13 L min(-1) m(-2) (2 SD = 1.04L min(-1) m(-2)) (r2 = 0.86, P < 0.0001).
CONCLUSIONS: In comparison with PAOP, ITBVI seems a more reliable indicator of cardiac preload in patients undergoing liver transplantation.