Influence of extravascular lung water on transpulmonary thermodilution-derived cardiac output measurement.

OBJECTIVE: The transpulmonary thermo-dye dilution technique enables assessment of cardiac index (CI) intrathoracic blood volume index (ITBVI) and extravascular lung water index (EVLWI). Since the extent of lung edema may influence the reliability of CI measurement by transpulmonary thermodilution due to loss of indicator, we analyzed the impact of EVLWI on transpulmonary thermodilution-derived CI in critically ill patients.
DESIGN: Retrospective, clinical study.
SETTING: Surgical intensive care unit in a university hospital PATIENTS AND METHODS: With ethics approval we analyzed data from 57 patients (38 men, 19 women; age range 18-79 years) who, for clinical indication, underwent hemodynamic monitoring by transpulmonary thermo-dye dilution and pulmonary artery thermodilution (572 measurements). All patients were mechanically ventilated and had received a femoral artery thermo-fiberoptic and pulmonary artery catheter which were connected to a computer system (Cold-Z021, Pulsion Medical Systems, Munich, Germany). For each measurement, 15-17 ml indocyanine green(4-6 degrees C) was injected central venously. Injections were made manually and independently from the respiratory cycle. Linear regression was used for statistical analysis. INTERVENTIONS AND MAIN
RESULTS: The difference between transpulmonary and pulmonary artery thermodilution CI was not correlated with EVLWIfor all measurements (n=572, r=0.01, p=0.76) and when using only the first simultaneous measurement (n=57, r=0.08, p=0.56). Furthermore, EVLWI was not correlated with transpulmonary thermodilution CI (n=572, r=0.07, p=0.08). Coefficient of variation for transpulmonary thermodilution CI was 7.7+/-4.3%.
CONCLUSION: Measurement of cardiac output by transpulmonary thermodilution is not influenced by EVLWI in critically ill patients and loss of indicator as the underlying reason is probably overestimated.