Association between preoperative hypoalbuminemia and the risk of allogeneic red blood cell transfusion in major surgery: a retrospective cohort study

BACKGROUND: Serum albumin plays an important role in maintaining colloid osmotic pressure and fluid balance. Hypoalbuminemia has been identified as a predictor of postoperative mortality and morbidity. However, the impact of preoperative hypoalbuminemia on intraoperative red blood cell (RBC) transfusion has seldom been investigated. MATERIAL AND METHODS: This was a single-center retrospective cohort study conducted at a general tertiary teaching hospital in Beijing. The study included adult patients who underwent representative elective major surgeries between 2018 and 2022. The exposure was preoperative hypoalbuminemia, defined as a serum albumin concentration of less than 35 g/l. The primary outcome was the transfusion of allogeneic RBCs during surgery or within three days postoperatively. Twenty confounders related to demographic characteristics, comorbidities, and procedural complexity were adjusted for using multivariable logistic regression and inverse probability of treatment weighting (IPTW). Dose-response analysis, subgroup analysis based on preoperative hemoglobin levels, and mediation analysis of intraoperative blood loss were also performed. RESULTS: A total of 15 336 patients were included, of whom 678 (4.4%) had preoperative hypoalbuminemia. Perioperative RBC transfusions were administered to 1804 patients (11.8%). A significant association between preoperative hypoalbuminemia and the risk of perioperative RBC transfusion was observed when adjusting for confounders using logistic regression [odds ratio (OR): 2.04, 95% confidence interval (CI): 1.65-2.54, P < 0.001] or IPTW (OR: 1.89, 95% CI: 1.47-2.44, P < 0.001). This association became stronger as albumin level decreased (P for trend