A Propensity-Matched Cohort Study of Intravenous Iron versus Red Cell Transfusions for Preoperative Iron-Deficiency Anemia

BACKGROUND: While preoperative anemia is associated with adverse perioperative outcomes, the benefits of treatment with iron replacement versus red blood cell (RBC) transfusion remain uncertain. We used a national database to establish trends in preoperative iron-deficiency anemia (IDA) treatment and to test the hypothesis that treatment with preoperative iron may be superior to RBC transfusion. METHODS: This study is a propensity-matched retrospective cohort analysis from 2003 to 2023 using TriNetX Research Network, which included surgical patients diagnosed with IDA within 3 months preoperatively. After matching for surgery type and comorbidities, we compared a cohort of patients with preoperative IDA who were treated with preoperative intravenous (IV) iron but not RBCs (n = 77,179), with a cohort receiving preoperative RBCs but not IV iron (n = 77,179). Propensity-score matching was performed for age, ethnicity, race, sex, overweight and obesity, type 2 diabetes, hyperlipidemia, essential hypertension, heart failure, chronic ischemic heart disease, neoplasms, hypothyroidism, chronic kidney disease, nicotine dependence, surgery type, and lab values from the day of surgery including ferritin, transferrin, and hemoglobin split into low (<7 g/dL), medium (7–<12 g/dL), and high (≥12 g/dL) to account for anemia severity. The primary outcome was 30-day postoperative mortality with the secondary outcomes being 30-day morbidity, postoperative hemoglobin level, and 30-day postoperative RBC transfusion. RESULTS: Compared with RBC transfusion, preoperative IV iron was associated with lower risk of postoperative mortality (n = 2550/77,179 [3.3%] vs n = 4042/77,179 [5.2%]; relative risk [RR], 0.63, 95% confidence interval [CI], 0.60–0.66), and a lower risk of postoperative composite morbidity (n = 14,174/77,179 [18.4%] vs n = 18,632/77,179 [24.1%]; RR, 0.76, 95% CI, 0.75–0.78) (both P = .001 after Bonferroni adjustment). Compared with RBC transfusion, IV iron was also associated with a higher hemoglobin in the 30-day postoperative period (10.1 ± 1.8 g/dL vs 9.4 ± 1.7 g/dL, P = .001 after Bonferroni adjustment) and a reduced incidence of postoperative RBC transfusion (n = 3773/77,179 [4.9%] vs n = 12,629/77,179 [16.4%]; RR, 0.30, 95% CI, 0.29–0.31). CONCLUSIONS: In a risk-adjusted analysis, preoperative IDA treatment with IV iron compared to RBC transfusion was associated with a reduction in 30-day postoperative mortality and morbidity, a higher 30-day postoperative hemoglobin level, and reduced postoperative RBC transfusion. This evidence represents a promising opportunity to improve patient outcomes and reduce blood transfusions and their associated risk and costs.