Postoperative anaemia and long‐term survival following cardiac surgery: a multicentre, retrospective, observational study

INTRODUCTION: Pre-operative anaemia is associated with adverse outcomes following cardiac surgery. However, the prognostic impact of postoperative anaemia is characterised incompletely. We examined whether anaemia at hospital discharge independently predicts long-term survival and characterised haemoglobin recovery trajectories during the first postoperative year. METHODS: for both). The primary outcome was overall survival from surgery to death or censoring at end of follow-up. Cox proportional hazards regression assessed associations between anaemia at discharge and mortality, adjusting for age, sex, pre-operative haemoglobin and comorbidities. Restricted cubic splines examined non-linear relationships between haemoglobin and mortality. RESULTS: At discharge, 23,935 (93.1%) patients were anaemic (8384 (32.6%) mild anaemia and 15,551 (60.5%) moderate-severe anaemia). Moderate-severe anaemia was independently associated with worse survival (hazard ratio 1.11, 95%CI 1.01-1.21, p = 0.034) in adjusted analysis. Cubic spline analysis revealed a steep, non-linear relationship between pre-operative haemoglobin and mortality, whereas discharge haemoglobin provided limited prognostic information beyond baseline characteristics and surgical complexity. Haemoglobin recovery plateaued around 4 months after discharge, but the average haemoglobin level remained below baseline even after 1 year. DISCUSSION: Postoperative anaemia showed a weak independent association with long-term mortality, in contrast to the clear dose-response relationship observed for pre-operative anaemia. The near-universal prevalence of postoperative anaemia and incomplete haemoglobin recovery at 1 year support further trials of peri-operative anaemia management.