Association between hemoglobin levels and ICU length of stay in Traumatic Brain Injury Patients: A retrospective cohort study from MIMIC database

Background: In traumatic brain injury patients, the optimal hemoglobin level is uncertain, and its impact on intensive care unit length of stay is unclear. Objective: To investigate the correlation between hemoglobin levels and intensive care unit length of stay in traumatic brain injury patients. Methods: This retrospective cohort study used the Medical Information Mart for Intensive Care - IV version 3.0 database. Hemoglobin levels within the first 24 hours of intensive care unit admission were the primary exposure, and intensive care unit length of stay was the primary outcome. Data on 35 variables were collected, with missing data imputed via k-Nearest Neighbors. Hemoglobin was analyzed as a continuous and categorical variable. Linear regression, restricted cubic spline models, trend tests, subgroup, and interaction analyses were used to examine their relationship. Results: The study included 2,333 patients. In multivariate linear regression, higher hemoglobin was linked to lower intensive care unit length of stay (adjusted β=-0.54, 95% CI=-0.94~-0.15, P=0.007), indicating an inverse relationship.Hemoglobin tertile analysis showed mean intensive care unit length of stay of 3.2, 2.9,and 2.7 days (Q1-Q3).After covariate adjustment,Q3 had a β of -1.78 (95% CI:-2.74~-0.82, P<0.001) versus Q1.Trend analysis found significant group differences (P for trend<0.05). Restricted cubic spline analysis revealed an "L"-shaped relationship (P for non-linearity=0.03), with a breakpoint at 9.277 g/dL. Subgroup analyses confirmed stable results. Conclusion : An L-shaped association exists between hemoglobin levels and intensive care unit length of stay, with a breakpoint at 9.277 g/dL. Above this level, a significant negative correlation was observed.