Limits and pitfalls of haemodynamic monitoring systems in liver transplantation surgery.

Cardiac output (CO) and other hemodynamic variables measured during liver transplantation are often obtained by pulmonary artery catheter (PAC) and in many centers by the transthoracic thermodilution method and/or intraoperative transesophageal echocardiography (TEE). Newer non-invasive technology, such as the PiCCO(®) system, the LiDCO(®) Plus monitor, and the FloTrac/Vigileo(®), have been proposed as more reflective of ongoing hemodynamic response to intraoperative manoeuvres. In contrast to the standard "semicontinuous" thermodilution method, which gives information over a set period of time, the new monitoring systems use a different time period or measure over a running several beat average. It has been stated that algorithms based on arterial pulse contour analysis can potentially facilitate rapid diagnosis and prompt therapeutic interventions. However, as the use of these technologies has spread, so has the understanding of their limitations. This has led to an increased scepticism among the previously enthusiastic "pioneering" practitioners. Given the poor agreement reported in various studies on liver transplant surgery between PAC and the new "calibrated" and "uncalibrated"-derived measurements, multicenter trials aiming at evaluating the performance of the non-invasive methods in different hemodynamic conditions and dedicated monitoring-driven treatment protocols are necessary.