THERMODILUTION CARDIAC-OUTPUT MAY BE INCORRECT IN PATIENTS ON VENOVENOUS EXTRACORPOREAL LUNG ASSIST

Cardiac output measurement is part of routine monitoring in critically ill patients. In patients on extracorporeal lung assist, thermodiluti on cardiac output measurement may lead to erroneous results caused by indicator loss into the extracorporeal circuit. Seven patients on veno venous extracorporeal lung assist were studied using different extraco rporeal blood flows. We compared conventional thermodilution cardiac o utput determinations with dye dilution cardiac output measurement, wit h dye injection into the pulmonary artery. The latter method is not af fected by the extracorporeal circuit. The conventional thermodilution method overestimated cardiac output up to a maximum of 300%, providing results up to 10 L/min higher than true cardiac output. The mean diff erence between thermodilution and true cardiac output as determined by dye dilution with pulmonary artery indicator injection was 3.0 +/- 2. 41 L/min. There was no correlation between thermodilution cardiac outp ut values and true cardiac output (r = 0.06). We conclude that convent ional thermodilution is not a suitable method for cardiac output measu rement in patients on extracorporeal lung assist, especially if high e xtracorporeal blood flows are applied.