Inpatient Metabolic Panel Trajectories Improve 6-Month Mortality Prognostication after Severe Traumatic Brain Injury

The International Mission for Prognosis and Analysis of Clinical Trials (IMPACT) in traumatic brain injury (TBI) only includes data from hospital admission as predictors. Including updated physiological data after hospital admission would likely improve prognostic ability above the IMPACT model alone. We sought to evaluate differences in the daily trajectory of clinical metabolic panels (e.g., glucose, sodium, platelets, hemoglobin) for the first 7 days post-severe TBI (sTBI). This is a prospective cohort study of patients with sTBI with Glasgow Coma Scale (GCS) ≤8. Intake GCS was conducted by a neurosurgeon or neurosurgical resident to ensure GCS at presentation was related to the brain injury and not other factors. We compared daily metabolic panel trajectories between survivors to 6 months and nonsurvivors to 6 months using ordinal mixed-effects models. Dichotomizing trajectories as "high" or "low" was set to 4+ of the first 7 days postinjury to represent a majority of the first postinjury week. We then examined the added prognostic value of these trajectories compared with the IMPACT-extended model for 6-month mortality. Included patients (n = 572) were 40.4 ± 17.1 years of age, 79.4% male, and 38.4% had died by 6 months postinjury. The likelihood ratio tests (LRT) comparing the ordinal trajectories of sodium and platelets were statistically significant after false discovery correction (sodium: likelihood ratio = 51.0; adj. p < 0.001; platelets: likelihood ratio = 16.0; adj. p = 0.003), indicating that the overall trajectory over 7 days differs between groups. The LRT comparing the trajectories of glucose and hemoglobin were not statistically significant (p = 0.21-0.98). The models identified a divergence in platelet values on days 6 and 7, where nonsurvivors to 6 months had lower odds (OR = 0.27-0.41) of being in higher platelet categories than survivors to 6 months on those days. The IMPACT-only model had an area under the curve (AUC) for 6-month mortality of 0.85 and a Hosmer-Lemeshow p value = 0.68. The IMPACT-biomarker trajectory model had an AUC for 6-month mortality of 0.87 (DeLong's test p value of 0.005) and a Hosmer-Lemeshow p value of 0.16. Trajectory of metabolic panel labs in the first week postinjury yields meaningful improvements in prognostic ability for the individual patient.