Determining sex-specific preoperative haemoglobin levels associated with intraoperative red blood cell transfusion in cardiac surgery: a retrospective cohort study

Abstract

Background: Anaemic cardiac surgery patients are at greater risk of intraoperative red blood cell transfusion. This study questions the application of the World Health Organization population-based anaemia thresholds (haemoglobin <120 g L−1 in non-pregnant females and <130 g L−1 in males) as appropriate preoperative optimisation targets for cardiac surgery. Methods: A retrospective cohort study was conducted on adults ≥18 yr old undergoing cardiopulmonary bypass surgery. Logistic regression was applied to define sex-specific preoperative haemoglobin concentrations with reduced probability of intraoperative red blood cell transfusion for cardiac surgery patients. Results: Data on 4384 male and 1676 female patients were analysed. Binarily stratified multivariable logistic regression odds of receiving intraoperative red blood cell transfusion increased in cardiac surgery patients >45 yr old (odds ratio [OR] 1.84; 95% confidence interval [CI] 1.33–2.55), surgery urgency <30 days (OR 2.03; 95% CI 1.66–2.48), combined coronary artery bypass grafting and valve surgery, or other surgery types (OR 2.24; 95% CI 1.87–2.67), and female sex (OR 1.92; 95% CI 1.62–2.28). The odds decreased by 8.4% with each 1 g L−1 increase in preoperative haemoglobin (OR 0.92; 95% CI 0.91–0.92). Logistic regression predicted females required a preoperative haemoglobin concentration of 133 g L−1 and males 127 g L−1 to have a 15% probability of intraoperative transfusion. Conclusions: The World Health Organization female anaemia threshold of haemoglobin <120 g L−1 disproportionately disadvantages female cardiac surgery patients. A preoperative haemoglobin concentration ≥130 g L−1 in adult cardiac surgery patients would minimise their overall probability of intraoperative red blood cell transfusion to <15%.