Abstract
Abstract
Preoperative anaemia is common in adults undergoing cardiac surgery and may identify patients at increased perioperative risk. This systematic review and meta-analysis synthesised contemporary observational evidence in accordance with PRISMA 2020. Five databases were searched for peer-reviewed English language studies published from 2017 to July 2026. Random effects meta-analyses used restricted maximum likelihood estimation with Hartung-Knapp confidence intervals; crude exact count estimates were synthesised primarily and adjusted estimates separately. Fourteen observational cohort studies involving 74,571 adults, including 17,349 (23.3%) with anaemia, were included. Preoperative anaemia was associated with red cell transfusion (OR, 3.66; 95% CI, 2.14-6.24), acute kidney injury or renal failure (OR, 2.43; 95% CI, 1.84-3.21), early mortality (OR, 2.11; 95% CI, 1.40-3.17), and postoperative infection (OR, 1.49; 95% CI, 1.21-1.82), but not postoperative stroke (OR, 1.16; 95% CI, 0.43-3.17). Certainty was low for renal outcomes and very low for the other outcomes. Preoperative anaemia is an important perioperative risk marker, particularly for transfusion and renal complications, although causality cannot be established.