Background: Intubated pediatric patients with isolated traumatic brain injury (TBI) are a diagnostic challenge for early detection of altered cerebral physiology instigated by trauma-induced increased intracranial pressure (ICP) while preventing secondary neuronal damage (secondary insult detection) and assessing the effects of increased ICP therapeutic interventions (3% hypertonic saline [HTS]). Invasive brain tissue oxygen monitoring is guiding new intensive care unit TBI management but is not pediatric emergency department (PED) readily accessible. Objective measurements on pediatric isolated TBI-altered bihemispheric cerebral physiology and treatment effects of 3% HTS are currently lacking. Cerebral oximetry can assess increased ICP-induced abnormal bihemispheric cerebral physiology by measuring regional tissue oxygenation (r c SO 2 ) and cerebral blood volume index (CBVI) and the mechanical cerebrospinal fluid removal effects on the increased ICP-induced abnormal bihemispheric cerebral physiology.In the PED intubated patients with isolated TBI, assessing the 3% HTS therapeutic response is solely by vital signs and limited clinical assessment skills. Objective measurements of the 3% HTS hyperosmolar effects on the PED isolated TBI patients' altered bihemispheric cerebral physiology are lacking. We believe that bihemispheric r c SO 2 and CBVI could elucidate similar data on 3% HTS impact and influence in the intubated isolated TBI patients.Objective: This study aimed to analyze the effects of 3% HTS on bihemispheric r c SO 2 and CBVI in intubated patients with isolated TBI.Methods: An observational, retrospective analysis of bihemispheric r c SO 2 and CBVI readings in intubated pediatric patients with isolated TBI receiving 3% HTS infusions, was performed.Results: From 2010 to 2017, 207 intubated patients with isolated TBI received 3% HTS infusions (median age, 2.9 [1.1-6.9 years]; preintubation Glasgow Coma Scale score, 7 [6][7][8]). The results were as follows: initial pre−3% HTS, 43% (39.5% to 47.5%; left) and 38% (35% to 42%; right) for r c SO 2 < 60%, and 8 (−28 to 21; left) and −15