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FLOTRAC/VIGILEO The FloTrac/Vigileo system (Edwards Lifesciences, Irvine, California, USA) also utilizes a blood flow sensor, attached to a standard arterial catheter. Cardiac output is calculated every 20 seconds using a recently upgraded algorithm. The specific vascular compliance is updated every minute and is based on age, height, gender, and weight and waveform characteristics. Unlike other pulse contour devices, the FloTrac/Vigileo does not require external calibration. The performance of the FloTrac/Vigileo system has also been researched in a range of clinical situations. To date, the data regarding the accuracy of the Vigileo system in comparison with both PACs and PiCCO devices have been conflicting. Despite software upgrades, a recent study of 21 critically ill patients in an intensive care unit showed underestimation of cardiac output by more than 2 litre min−1 in 41 percent of measurements.6 However, the advantage of this device being less invasive than others may outweigh this reduction in reliability and it has been suggested that the FloTrac/Vigileo may be more useful for measuring trends than absolute values. Pulse contour analysis monitors rely on an optimal arterial signal. Over- or under-damped traces may lead to inaccurate cardiac output measurement. Arrhythmias, aortic regurgitation, and the use of an intra-aortic balloon pump all affect the pulse contour and have been shown to affect accuracy. Arrhythmia also affects SVV data. Although some currently available minimally invasive cardiac output monitors may be of clinical yield in optimizing the hemodynamic status of critically ill neurologic patients, they all have their own sources of potential error. Clinicians should be cognizant of their benefits as well as their potential sources of error and clinical limitations. Funk DJ, Moretti EW, Gan TJ. Minimally invasive cardiac output, Anesth Analg, 2009, vol. 108 (pg. 887 – 97 ) Hofer CK, Ganter MT, Zollinger A. What technique should I use to measure cardiac output? Curr Opin Crit Care, 2007, vol. 13 (pg. 308 – 17) Reuter DA, Huang C, Edrich T, et al. Cardiac output monitoring using indicator-dilution techniques: basics, limits, and perspectives, Anesth Analg, 2010, vol. 110 (pg. 799 – 811) 32


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