A comparison of pulse contour wave analysis and ultrasonic cardiac output monitoring in the critically ill

Cardiac output (CO) is a key determinant of major organ blood flow and solute delivery to drug eliminating organs. As such, CO assessment is a key covariate in understanding altered drug handling in the critically ill. Newer minimally-invasive devices are providing unique platforms for such an application, although comparison data are currently lacking. In this study we evaluated the Vigileo® (Edwards Lifesciences, Irvine, CA, USA) and USCOM® (USCOM Ltd, Sydney, NSW) devices in 62 critically ill patients requiring antibacterial therapy. The mean CO _Vigileo and CO _USCOM for the first paired measurements were 8.20±2.65 l/minute and 6.84±2.57 l/minute respectively (P <0.001). A significant correlation was evident in all patients (r=0.537, P <0.001), although the recorded bias was large (1.36±2.51 l/minute, limits of agreement -3.6 to +6.3 l/minute). The overall percentage error was 65%. There was an improved correlation in those admitted with sepsis (r=0.639, P <0.001) compared to trauma (r=0.373, P=0.066), although bias, precision and percentage error were similar in both subgroups. In 54 patients a second paired assessment was obtained at three hours. A weak, although significant correlation (r=0.377, P=0.005) was observed suggesting that gross trends over time were similar. In conclusion, our findings demonstrate poor agreement between these techniques suggesting that these devices are not simply interchangeable when assessing CO in a research or clinical setting.