The burden of pre-operative anaemia and postoperative outcomes in 15 166 surgical patients from a public hospital in Brazil: A retrospective cohort study.

Background: Preoperative anaemia is associated with poor postoperative outcomes; however, few studies have reported its prevalence in developing countries and its association with significant postoperative outcomes.

Objective: We aimed to identify the prevalence of anaemia and its association with postoperative outcomes in a major public hospital in Brazil.

Design: Retrospective cohort study.

Setting: Single-centre, 860-bed, quaternary university-affiliated teaching hospital in Southern Brazil.

Patients: We included adult patients who had undergone surgery between 2015 and 2019. Main outcome measures: The main outcome was the in-hospital 30-day postoperative mortality. According to the World Health Organisation, we defined anaemia and its sub-classification (mild, moderate, and severe). We developed Poisson regression models to examine the association between preoperative anaemia and outcomes.

Results: We included 15 166 patients, of whom 6387 (42.1%) were anaemic. After adjustment for confounding factors, patients with anaemia had an increased risk of in-hospital 30-day postoperative mortality (relative risk (RR) 1.69, 95% confidence interval (CI) 1.44 to 1.99, P < 0.001). Mild [relative risk (RR) 1.38, 95% CI 1.12 to 1.71, P = 0.003], moderate (RR 1.73, 95% CI 1.43 to 2.10, P < 0.001), and severe anaemia (RR 2.43, 95% CI 1.92 to 3.07, P < 0.001) were associated with the primary outcome. Anaemia increased the transfusion risk (RR 4.44, 95% CI 3.90 to 5.06, P < 0.001) and postoperative intensive care unit (ICU) admission (RR 1.09, 95% CI 1.04 to 1.16, P = 0.001).

Conclusions: Four out of 10 patients had anaemia. These patients had an increased risk of adverse postoperative outcomes. Comprehension of the magnitude and impact of anaemia is essential to establish interventions in low-resource scenarios to optimise the patient's journey.

Study registration: Institutional Review Board Registration number 40522820000005327 (Brazilian CEP/CONEP System, available in https://plataformabrasil.saude.gov.br/).