Early hemoglobin levels and mortality in non-transfused TBI patients: A linear, inverse association

Hemoglobin (Hb) concentration is frequently altered following traumatic brain injury (TBI), yet its independent prognostic value in the absence of blood transfusion remains unclear. This study investigated the association between mean Hb during the first five ICU days and mortality in non-transfused TBI patients. Using data from the MIMIC-IV database, we conducted a retrospective cohort study including adult TBI patients with ICU stay > 24 h who received no packed red blood cell transfusion. The primary exposure was mean Hb over the first five ICU days, and outcomes were 30-day and 90-day all-cause mortality. Among 1,880 patients, each 1 g/dL increase in mean Hb was associated with a 15% reduction in 30-day mortality (adjusted HR 0.85, 95% CI 0.79-0.91) and a 13% reduction in 90-day mortality (adjusted HR 0.86, 95% CI 0.81-0.92) after multivariable adjustment. Restricted cubic spline analysis demonstrated a linear inverse relationship at both time points. Subgroup analyses revealed that the protective association was significantly modified by the presence of congestive heart failure and atrial fibrillation at 30 days, and by atrial fibrillation and sepsis at 90 days, with attenuation of the protective effect in patients with these comorbidities. Sensitivity analyses confirmed the robustness of these findings. Higher early Hb levels are independently and linearly associated with lower mortality in non-transfused TBI patients, suggesting that sustained anemia during the acute phase may represent an independent risk factor. The prognostic value of Hb varies according to underlying cardiovascular comorbidities and sepsis, highlighting the time‑dependent nature of this association. These findings underscore the need for further research into non-transfusion strategies for anemia management in this population.