Dear Sir: Extended hemodynamic monitoring by the transpulmonary thermodilution technique, which has been shown to be sufficiently accurate when compared to the double-indicator technique [1], has the potential for reduced length of mechanical ventilation and stay in the ICU [2]. However, reliability of this technique has been questioned, i.e., during extracorporeal circulation. Previously, it was shown in patients with preserved cardiac output (CO) that running renal replacement therapy has no clinically relevant impact [3]. Here, data are provided on the influence of a pumpless extracorporeal lung assist system on transpulmonary thermodilution-derived variables. A 70-year-old woman (162 cm, 60 kg) underwent uneventful elective upper lung sleeve resection for cancer. Unfortunately, she developed acute respiratory distress syndrome (ARDS) 5 days after surgery. She was re-admitted to the ICU and underwent intubation of the trachea for mechanical ventilation. For extended hemodynamic monitoring, a 5F-thermistor catheter (PV20L15, Pulsion Medical Systems, Munich, Germany) was placed into the left A. femoralis, which was connected to a PiCCOplus monitor (Pulsion Medical Systems AG, Munich, Germany). Furthermore, a right femoral 12F-dialysis double-lumen catheter (BCDL2000, Bionic Medizintechnik, Friedrichsdorf, Germany) was placed for continuous veno-venous hemofiltration (Edwards bm11 and bm14, Unterschleisheim, Germany). Unfortunately, she developed severe respiratory acidosis (PaCO2 101 mmHg, pH 7.12) and therefore was treated by a pumpless extracorporeal lung assist system (iLA Membrane Ventilator, Novalung, Hechingen, Germany). For this, a 13-F catheter was placed into the right A. femoralis and a 15-F catheter into the left V. femoralis. Flow in the extracorporeal circuit Q(ELA) was assessed by novalung flow c (Novalung, Hechingen, Germany). Hemodynamic variables based on thermodilution were obtained in triplicate by central venous (V. cava superior) injections of 15 ml 0.9% NaCl \ 8 C. For CO2 elimination, O2 flow via the membrane was 12 l/min throughout. At all time points (Table 1), ventilator settings (Evita 2 dura, Draeger, Lubeck, Germany) remained unchanged: BiPAP, FiO2 0.8, PiP 30 mbar, PEEP 12 mbar, respiratory rate 20/min, tidal volume ca. 280 ml, minute volume 3.3 l/min and compliance 10 ml/mbar. So far, studies on the effects of extracorporeal systems on the accuracy of cardiac output measurement are limited. In general, the higher the flow of the extracorporeal circuit, the higher the overestimation of cardiac output by the thermodilution technique [4]. From theory, any extracorporeal circuit with partially removing the indicator from the system may result in a more or less
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