What is the optimal type of fluid to be used for peri-operative fluid optimisation directed by oesophageal Doppler monitoring?

The objective of this review was to determine the optimal type or class of intravenous fluid to be used during peri-operative patient optimisation guided by oesophageal Doppler monitoring and to identify future directions for research. We undertook a literature review of patients undergoing major (general, colorectal, orthopaedic and urological) surgery, whose fluid therapy was managed using peri-operative oesophageal Doppler monitoring. We identified 10 studies that included 891 randomised patients. A variety of regimens and types of fluid were used in association with oesophageal Doppler monitoring, including crystalloid, gelatin and hydroxyethyl starch. A wide variety of hydroxyethyl starch preparations were used, including high molecular weight and highly substituted hetastarches, and lower molecular weight tetrastarches. Most studies were of high quality, associated with reduced hospital stay, but underpowered to evaluate other outcomes. In units with established enhanced recovery facilities, the benefits of colloid based on oesophageal Doppler monitoring were not reproduced. There is little evidence to support preferential use of any particular type of fluid during oesophageal Doppler guided optimisation; however, routine use of colloids is associated with significantly higher costs and may increase hospital stay. Furthermore, many of these fluids have not been evaluated in patient populations in whom optimisation is being applied or proposed, and the potential for harm cannot be excluded. Recommendations for future studies are provided, including adequate power for primary end points beyond hospital stay and adequate follow-up, and inclusion of a crystalloid comparison group.