These can be used either to predict a patient likely to respond to a volume challenge or to carefully monitor the response to a fluid bolus. This therefore provides a sophisticated and sensitive mechanism for titrating intravenous fluids to complex patients. Benefit has been demonstrated with fluid loading alone to maximize stroke volume, using these Crenolanib AML technologies [48,50]. Targeting of the pulse pressure variation in mechanically ventilated patients to a value of less than 10% with fluid challenges has been demonstrated to improve post-operative outcome and reduce length of hospital stay [51].Fluid therapy as guided by the oesophageal Doppler (Deltex Medical Ltd, Chichester, UK) reduces mortality and hospital stay [31,52,53]. The oesophageal Doppler is well tolerated and can be used throughout the entire peri-operative period.

It has little bias and high clinical agreement when compared with the PAC for monitoring changes in cardiac output [54]. FTc is inversely proportional to systemic vascular resistance and is sensitive to changes in left ventricular preload [55]. It may also be a more sensitive indicator of cardiac filling than pulmonary artery occlusion pressure [56]. Improved outcome as demonstrated by faster return of gastrointestinal function, a reduction in post-operative complications and shortened hospital stay was demonstrated when using the oesophageal Doppler for goal-directed fluid administration (that is, targeting stroke volume and FTc to maximize CI) during major surgery [48].

A meta-analysis of five RCTs of 420 patients undergoing major abdominal surgery showed fewer complications, less requirement for inotropes, faster return of gastro-intestinal function, fewer ICU admissions and shorter hospital stay in patients who received oesophageal Doppler-guided haemodynamic management [50].The LiDCOplus system (LiDCO Ltd, Cambridge, UK) is also well validated [57]. In 2005 Pearse and colleagues [38] conducted a RCT of post-operative GDT in high-risk general surgical patients using colloid and dopexamine to achieve a 2 or conventional management DO2I of 600 ml/minute/m using the LiDCOplus to measure CO. There were fewer complications in the control group (44% versus 68%), less complications per patient and a shorter hospital stay, although there was no difference in 28- or 60-day mortality.

Several studies have shown that the PiCCO system (PULSION Medical Systems, Munich, Germany) is also a reliable method of assessing cardiac preload and may actually be more sensitive than the PAC [58-60]. Goepfert and colleagues [61] devised a GDT algorithm based on targeting global end-diastolic volume index, an indicator of cardiac preload as measured GSK-3 by PiCCO to achieve a goal of >640 ml/m2 and CI >2.5 l/minute/m2 in patients undergoing elective coronary artery bypass grafting surgery.