BACKGROUND: Use of the transpulmonary thermodilution technique has been suggested for extended hemodynamic monitoring in critically ill patients. However, many of these patients also require renal replacement therapy (RRT). Therefore, we analyzed the influence of venovenous RRT on measurement of cardiac index (CI), intrathoracic blood volume index (ITBVI), and extravascular lung water index (EVLWI). METHODS: We studied 24 consecutive critically ill patients (15 males, 9 females; age 39-81, mean 62 yr) who had received a clinically indicated 5F femoral arterial catheter (PV2015L20, Pulsion Medical Systems, Germany), which was connected to a monitor (PiCCOplus, Pulsion Medical Systems, Germany). A 12F dialysis catheter (Trilyse Expert, Vygon) was either advanced from the vena femoralis into the vena cava inferior (n = 12) or placed into the superior vena cava (n = 12). Patients continuously received heparin for anticoagulation. Hemodynamic measurements were performed in triplicate by central venous injection of saline (15 mL,