Association between hemoglobin and in-hospital mortality in critically ill patients with sepsis: evidence from two large databases

Background: The relationship between baseline hemoglobin levels and in-hospital mortality in septic patients remains unclear. This study aimed to clarify this association in critically ill patients with sepsis.

Methods: Patients with sepsis were retrospectively identified from the Medical Information Mart for Intensive Care-IV (MIMIC-IV 2.2) and eICU Collaborative Research Database (eICU-CRD). Multivariate logistic regression analysis and restricted cubic spline regression were used to investigate the association between hemoglobin and the risk of in-hospital mortality. Additionally, a two-part linear regression model was used to determine threshold effects. Stratified analyses were also performed.

Results: A total of 21,946 patients from MIMIC-IV and 15,495 patients from eICU-CRD were included in the study. In-hospital mortality was 14.95% in MIMIC-IV and 17.40% in eICU-CRD. Multivariate logistic regression showed that hemoglobin was significantly and nonlinearly associated with the risk of in-hospital mortality after adjusting for other covariates. Furthermore, we found a nonlinear association between hemoglobin and in-hospital mortality, with mortality plateauing at 10.2 g/dL. The risk of mortality decreased with increasing hemoglobin levels below 10.2 g/dL but increased when hemoglobin levels exceeded 10.2 g/dL. These findings were validated in the eICU-CRD dataset.

Conclusions: A nonlinear correlation between hemoglobin levels and in-hospital mortality was observed in patients with sepsis, with a threshold of 10.2 g/DL. These findings suggested that hemoglobin levels below or above the threshold may be associated with worse outcomes, warranting further investigation in prospective studies.