Noninvasive Cardiac Output Monitoring With Nexfin

To the Editor In a recent article, Bubenek-Turconi et al.1 compared 2 devices for measuring cardiac output (CO), namely the Nexfin (BMEYE, Amsterdam, Netherlands) and the pulmonary artery catheter. While we agree that the Nexfin is a safe, noninvasive, continuous, easy to use, and nonoperator dependent monitor, several limitations regarding the conduct of the study are of concern. First, CO measurements using the 2 methods were performed consecutively rather than simultaneously. Second, because multiple measurements of CO were performed in the same patients, the classic Bland-Altman analysis should be replaced by a technique dedicated to evaluating the agreement between both CO monitors with multiple observations per individual.2 Third, the patients were studied during stable hemodynamic conditions after elective cardiac surgery, and thus, the results cannot be extrapolated to all patients in whom hemodynamics may be changing. Fourth, 3 recent studies3–5 performed after a fluid challenge in cardiac surgical or critically ill patients showed weak correlation between changes in CO between both devices and percentage errors greater than 50%. Until phase III studies (clinical utility/outcome) in different subgroups of patients and surgeries, no definitive recommendation about the Nexfin should be made for clinical routine practice. Marc-Olivier Fischer, MD Jean-Luc Fellahi, MD, PhD Department of Anesthesiology and Critical Care University Hospital of Caen Caen, France email protected email protected