Significance of Initial Serum Phosphate Imbalance in Traumatic Brain Injury with and Without Concomitant Spinal Injuries: Retrospective Analysis

<b>Objectives</b>: On-admission phosphate imbalance (OAPI) in traumatic brain injury (TBI) is scarce in the literature, either alone or with concomitant spinal injuries (CSI). We aimed to explore the OAPI in TBI and hypothesized that OAPI has unfavorable outcomes in TBI as well as spinal injury. <b>Methods</b>: In this retrospective study, all hospitalized patients with TBI were reviewed, and their serum phosphate levels were measured upon admission. Outcomes included in-hospital mortality and neurological deficit. <b>Results</b>: Among 912 TBI patients, 13% had hyperphosphatemia (<i>n</i> = 118/912) and 30% had associated CSI (<i>n</i> = 272/912). Hypophosphatemia was found in two-thirds of TBI patients (<i>n</i> = 607/912). Thirteen patients of CSI group developed neurological deficits (4.8%) with hypophosphatemia. Serum phosphate levels were significantly correlated with serum potassium, magnesium, and lactate levels, as well as Injury Severity Score (ISS). The serum glucose-phosphate ratio was higher in patients with severe Glasgow Coma Scale (GCS). The overall mortality was 21.3% (47% had hyperphosphatemia, 17% had hypophosphatemia, and 18% had normophosphatemia). Multivariable analysis showed that hyperphosphatemia, high serum lactate, sodium, and potassium levels, high head Abbreviated Injury Scale (AIS), and low GCS were significantly associated with increased mortality. <b>Conclusions</b>: Hypophosphatemia was common in TBI patients regardless of the presence of spinal injuries and was observed in all patients with neurological deficits. Routine phosphate monitoring may help in early risk stratification and targeted management of TBI.