Cardiac output monitoring devices are commonly used in ICU patients. The most precise use direct measurement, which require artery cannulation. The gold standard is Swan-Ganz catheter, but it is a very invasive technique. PiCCO (Pulse index Continuous Cardiac Output) is the alternative way of haemodynamic monitoring. This technology is the easy, less invasive and cost-efficient tool for determining the main hemodynamic parameters of critically ill patients. It is based on two physical principles - transpulmonary thermodilution and pulse contour analysis. Both principles allow the calculation of haemodynamic parameters in critically ill patients. PiCCO method requires peripheral artery cannulation.