Electrolyte-derived clinical indices in traumatic brain injury: A narrative review

Traumatic brain injury (TBI) remains a significant global health burden. Electrolyte imbalances contribute to secondary brain injury by exacerbating cerebral edema, neuronal dysfunction, and increasing mortality. Electrolyte-derived clinical indices, based on routine laboratory tests, provide rapid and cost-effective tools for clinical decision-making and prognostication. This narrative review summarizes the current evidence on key electrolyte indices relevant to TBI, including the glucose-to-potassium ratio (GPR), plasma and effective osmolality, ion shift index (ISI), anion gap, Combined Electrolyte Disturbance, and Corrected Electrolytes. Each index is discussed in terms of its physiological basis, clinical utility, limitations, and prognostic relevance. Among these, GPR and osmolality have demonstrated substantial predictive value for mortality and functional outcomes, while ISI and combined electrolyte abnormalities are promising but require further validation. Adjustments to sodium and calcium levels, respectively, for glucose and albumin, prevent misdiagnosis and support more accurate treatment. These indices help bridge the gap between bedside monitoring and early risk stratification in the management of TBI. Their utility lies in their accessibility and potential to individualize care in both resource-rich and resource-limited settings. Future research should prioritize multicenter prospective validation studies, standardize threshold values, and develop clinical algorithms that integrate these indices into TBI care pathways. Such integration could improve early recognition of critical deterioration, guide therapeutic strategies, and ultimately enhance outcomes.