Consequences of anemia in geriatric hip fractures: how low is too low?

Background: The transfusion threshold for low hemoglobin (Hgb) in geriatric patients with hip fractures is widely debated. In certain populations, low Hgb is associated with poor outcomes. Our objective was to evaluate the relationship between lowest Hgb and outcome to identify the Hgb threshold where poor outcomes were more prevalent. Methods: This retrospective cohort study included consecutive patients with hip fractures, aged ≥60 years, evaluated at two level 1 trauma centers from 2018 to 2021. Patients who did not undergo operative fixation or had a length of stay <1 day were excluded. The primary endpoint was adverse outcome defined as the composite of myocardial infarction, stroke, new-onset arrhythmia or death. We compared lowest Hgb and possible confounders between patients with and without adverse outcomes. Classification and regression tree (CART) analysis was performed to identify the threshold for Hgb where adverse outcomes were more prevalent. Multivariate analysis was performed. Results: We evaluated 935 patients. Mean age was 80±10 years; admission Hgb was 12.5±1.7 g/dL. Diabetes was present in 20%, and 20% had coronary artery disease. Adverse outcomes were noted in 57 patients (6.1%). CART identified ≤7.1 g/dL as the Hgb threshold where adverse outcomes were more prevalent (15% vs. 4.1%, p<0.001). Additionally, a greater number of adverse outcomes were noted in the subgroup of patients having both a hemoglobin ≤7.1 g/dL and advanced age (age >79 years (22%)). After controlling for age, American Society of Anesthesiologist Physical Status Classification (ASA), antiplatelet medication, admission Hgb, time to operation and blood transfusions, lowest Hgb ≤7.1 g/dL remained a risk factor for adverse outcomes. Conclusions: In geriatric patients with isolated hip fractures, Hgb ≤7.1 g/dL is associated with a significantly higher rate of adverse outcomes. This risk was most pronounced in patients older than 79 years; particular care should be taken in this demographic. Level of evidence/study type: Level III/prognostic and epidemiological.