Mini invasive hemodynamic monitoring: from arterial pressure to cardiac output

To evaluate the Cardiac Output (CO) the standard invasive pulmonary artery catheter (PAC) is considered today the gold standard. The major criticism to the PAC is that its level of invasiveness is not supported by an improvement in patient's outcome. The interest to lesser and lesser invasive techniques is high. Therefore, the alternative techniques have been recently developed. Cardiac Output can be monitored continuously by different devices that analyze the arterial waveform to track changes in stroke volume (SV) and CO. The analysis of the arterial pressure wave to determine cardiac output is classified as Pulse Contour analysis or Pulse Pressure Analysis. Starting from a similar principle three main devices are now available on the market, with different algorithms and features: center dot PiCCO System (Pulsion Medical System, Munich, Germany) center dot LiDCO (TM) plus System (LidCO, Cambridge, UK) center dot Flotrac technology and Vigileo Monitor (Edwards Lifesciences, Irvine, CA, USA). The algorithm used by all these devices has been also implemented even with the analysis of the variation of stroke volume (SW) and of the pulse pressure (PPV). SW and PPV represent the variation of stroke volume and of the pulse pressure during the respiratory cycle. In sedated ventilated patients these indexes have proven to predict the response to a fluid challenge. A high variation (> 10-12%) identifies with good sensitivity and specificity responders and not responders.