Beneficial Effect of Pretreatment Hyperosmolality on Outcome in Severe Traumatic Brain Injury: Evidence from a South Korean Multicenter Registry and Propensity Score Matching Analysis.

Background: Hyperosmolar therapy has long been a cornerstone in managing increased intracranial pressure and improving outcomes in severe traumatic brain injury (TBI). This therapy hinges on elevating serum osmolality, creating an osmotic gradient that draws excess water from the brain's cellular and interstitial compartments and effectively reducing cerebral edema. Given this information, we hypothesized that the serum hyperosmolality prior to any treatment could significantly impact the clinical outcomes of patients with severe TBI, potentially mitigating secondary cerebral edema after trauma.

Methods: Data were extracted from the Korean Multi-center Traumatic Brain Injury data bank, encompassing 4628 patients with TBI admitted between January 2016 and December 2018. Of these, 507 patients diagnosed with severe TBI (Glasgow Coma Scale score < 9) were selected for comprehensive analysis across four data domains: clinical, laboratory, initial computed tomography scan, and treatment. Serum osmolality was assessed prior to treatment, and the hyperosmolar group was defined by a pretreatment serum osmolality exceeding 320 mOsm/L, whereas favorable outcomes were characterized by a modified Rankin Scale score of ≤ 3 at 6 months after trauma. Multivariate regression with receiver operating characteristic curve analysis and propensity score matching were used to dissect the data set.

Results: Multivariate analysis showed serum osmolality is significantly associated with clinical outcome in patients with severe TBI (p < 0.001). The optimal cutoff value for predicting favorable outcome was 331 mOsm/L, with a sensitivity of 38.9% and a specificity of 87.7%. Notably, the propensity score matching analysis comparing patients with pretreatment serum hyperosmolality with those without indicated a markedly improved functional outcome in the former group (32.5% vs 18.8%, p = 0.025).

Conclusions: The present study has uncovered a significant correlation between the pretreatment serum osmolality and the clinical outcomes of patients with severe TBI. These findings offer a novel perspective, indicating that a serum hyperosmolality prior to any treatment might potentially have a neuroprotective effect in patients with severe TBI.