Association between pre-operative borderline anaemia in women and outcome after coronary artery bypass grafting: data from the Netherlands Heart Registration.

Background: Haemoglobin concentration thresholds differ between men and women, with borderline anaemia (haemoglobin ≥ 12.1 and < 13.1 g dl -1 ) considered normal in women. However, this haemoglobin range may increase the risk of postoperative adverse outcomes after cardiac surgery.

Objectives: To determine if pre-operative borderline anaemia in women is associated with increased postoperative mortality and morbidity following coronary artery bypass grafting (CABG).

Design: A retrospective observational cohort study.

Setting: Data from The Netherlands Heart Registration, a national cardiac surgery registry, were used to analyse patients undergoing CABG from January 2013 to December 2020.

Patients: A cohort of 7802 women undergoing CABG was analysed, of whom 25% ( n  = 1963) had pre-operative borderline anaemia. Inclusion criteria were adult women undergoing isolated CABG; exclusion criteria included patients with severe anaemia or non-CABG procedures.

Main outcome measures: The primary outcome was 120-day mortality. Secondary outcomes included postoperative renal failure and need for packed red blood cell (PRBC) transfusion.

Results: Borderline anaemia in women was not significantly associated with 120-day mortality (adjusted odds ratio [AOR] 1.2; 95% CI 0.8 to 1.9; P  = 0.366). However, it was associated with an increased risk of renal failure (AOR 2.2; 95% CI 1.1 to 4.2; P  = 0.031) and PRBC transfusion (AOR 2.1; 95% CI 1.8 to 2.3; P  < 0.001).

Conclusions: Borderline anaemia, present in one-fourth of women undergoing CABG, does not increase mortality risk but is associated with higher postoperative morbidity, specifically renal failure and transfusion requirements.