The consequences of postoperative anemia remain unclear. Postoperative anaemia is more likely if there is pre-existing anemia, but also increased perioperative blood loss, frequent blood sampling, excess IV fluids (leading to hemodilution), sepsis, and inadequate nutritional intake after surgery. A nadir in Hb concentration is most often observed within the first 3-4 days after surgery. Postoperative anemia is believed to have deleterious effects on patient outcomes, including prolonged hospital stay, increased postoperative complications, and perhaps poor survival, but there is very little data to support this belief.~A recent consensus statement suggested that all patients recovering from major surgery (defined as blood loss > 500 ml or lasting > 2 h) and either had preoperative anemia or moderate-to-severe blood loss during surgery must be screened for anemia after surgery. Furthermore, this consensus group recommended that patients recovering from uncomplicated major surgery should have their Hb concentration measured for at least 3 days after surgery to detect anemia. As outlined above, this is problematic if there is fluid retention.~The role of IV iron for the treatment of postoperative anemia is unclear, with the most recent systematic review concluding that neither oral nor IV iron had a significant effect on patient quality of life or functional outcomes following surgery. A diagnosis of iron deficiency is very difficult in the postoperative period because the acute phase inflammatory response results in spuriously elevated ferritin levels, and several studies have demonstrated oral iron therapy is ineffective in this setting.~The investigators propose a study to investigate the incidence, extent, and outcomes of patients with anemia after major surgery, including an assessment of the amount of IV fluids administered in the immediate perioperative period.
Primary aim - To investigate the relationship between postoperative anaemia and patient-centred outcomes after major abdominal surgery.~Secondary aim - To determine whether a more liberal perioperative IV fluid strategy increases the risk of postoperative anaemia (haemodilution).~Hypothesis: Adults with anaemia in the immediate postoperative period following major abdominal surgery have a poorer quality of recovery and higher risk of complications, leading to poor disability-free survival when compared with patients without postoperative anaemia.