Effect of pleural fluid on the measurement of extravascular lung water by single transpulmonary thermodilution

Objective : To examine the reliability of the extravascular lung water value obtained by single transpulmonary thermodilution in the presence of a large amount of pleural fluid. Design : Observational clinical study. Setting : Medical intensive care unit of a tertiary teaching hospital. Patients and participants : Patients in whom an evacuation of pleural fluid was performed and who had a central venous catheter and a thermistor-tipped arterial thermodilution catheter (PiCCOplus system, Pulsion Medical Systems, Munich, Germany) for haemodynamic management. Interventions : None. Measurements and results : We included eight patients (mean age 669 /7.9 years) admitted to the medical intensive care unit with diagnoses of septic shock (n /4, of which two patients had ARDS) and cardiogenic shock (n /4). A total of 14 sets transpulmonary thermodilution measurements were obtained before and after evacuation of 7659 /330 ml pleural fluid (some patients received more than one thoracocenthesis). Data of the two samples were compared using the Wilcoxon matched pairs signed rank sum test. The extravascular lung water index increased from 11.39 /4.8 to 12.19 /4.9 ml/kg (p /0.041) and the pulmonary vascular permeability index increased from 1.99 /0.8 to 2.19 /0.9 (p /0.055). Conclusions : Fluid in the pleural space does not contribute to the volume transversed by the thermal indicator (‘‘cold’’) in single transpulmonary thermodilution measurements and does not cause an overestimation of the extravascular lung water.