REstrictive Versus LIbEral Fluid Therapy in Major Abdominal Surgery: RELIEF Study

The optimal fluid regimen, haemodynamic (or other) targets and fluid choice (colloid or crystalloid) for patients undergoing major surgery are based on rationales that are not supported by strong evidence. Practices vary substantially, guidelines are vague, small trials and meta-analyses are contradictory. The strongest and most consistent evidence, and biological plausibility because of tissue edema, supports a restrictive fluid strategy. But other evidence supports goal-directed therapy, requiring additional IV fluid. There is no good evidence that use and choice of colloids improves outcome. RELIEF will study the effects of fluid restriction, and the possible effect-modification of goal-directed therapy and colloids. The first will be randomly assigned; the latter will be measured covariates dictated by local practices and beliefs. Study Hypotheses A restrictive fluid regimen for adults undergoing major abdominal surgery leads to reduced complications and improved disability-free survival when compared with a liberal fluid regimen. Secondary hypothesis: The effects of fluid restriction are similar whether or not goal-directed therapy is used (assessed as a statistical test of interaction). A restrictive fluid regimen will reduce a composite of 30-day septic complications and mortality.