Hyponatremia on Initial Presentation Correlates with Suboptimal Outcomes after Traumatic Brain Injury

Hyponatremia is one of the most common metabolic disturbances found after traumatic brain injury (TBI). Previous reports have not investigated initial serum hyponatremia as a prognostic indicator for TBI outcomes. Records of 151 prospectively accrued, consecutive patients presenting with TBI to an urban Level I trauma center were reviewed and analyzed. Patients were dichotomized into two cohorts: hyponatremia on admission (initial serum sodium <135 mEq/L) and nonhyponatremia (initial serum eunatremia or hypernatremia). Initial serum hyponatremia was associated with higher Marshall score, lower initial Glasgow Coma Score (GCS), longer intensive care unit length of stay (ICU-LOS), and mortality. Analysis of patients who perished demonstrated that Marshall score and presence of initial serum hyponatremia had the largest influence on mortality. Lower initial serum sodium may be useful as an additional predictor of poor outcome among brain injured patients, and additional investigation is warranted. Multiple studies have evaluated radiologic and clinical findings (e.g., GCS) as prognostic indicators for outcomes of TBI, but few have evaluated the prognostic value of initial laboratory values for such outcomes.1 Hyponatremia is a common electrolyte abnormality after TBI—hyponatremia may be caused by posttraumatic syndrome of inappropriate antidiuretic hormone, cerebral salt wasting, or hypopituitarism.2 In the setting of TBI, hyponatremia is believed to worsen brain edema, increase intracranial pressure, and result in secondary brain injury.1 Piek et al. found that major electrolyte disturbances occurred in 59 per cent of TBI patients but did not correlate these disturbances with outcome.3 Moro et al. demonstrated that 16 per cent (50 of 298 patients over a 2-year period) of TBI patients present with hyponatremia but also did not correlate these findings with outcome.2 Data from the IMPACT study found similar rates of hyponatremia on initial presentation (11%) but did not focus on prognostication at admission.1 Our goal was to determine if initial serum hyponatremia on admission was associated with poor outcome for TBI patients compared with initial serum eunatremia or hypernatremia. Institutional Review Board approval was obtained, and protection of patient information was maintained throughout review and analysis. The prospectively accrued trauma registry of an urban Level I trauma center was interrogated for consecutive patients over the age of 13 who presented with TBI from January 2012 to May 2013. Patient demographics, initial laboratory values, vital signs, injury severity score (ISS), initial (postresuscitation) GCS, Marshall score, head Abbreviated Injury Scale (AIS Head), total length of stay (LOS), ICU-LOS, and in-hospital mortality were selected for analysis. Exclusion criteria included incomplete dataset; no patients were excluded. Hyponatremia was defined as initial serum sodium less than 135 mEq/L. Initial blood draws in the trauma bay routinely occur before crystalloid infusion as transport times in our urban center are minimal, leading to rare attempts at vascular access and minimal infusion by paramedics. Patients were dichotomized into hyponatremia and nonhyponatremia (i.e., eunatremia or hypernatremia) cohorts. Statistical analyses comparing abstracted data were performed using chi-squared analysis and Presented at the CHEST 2014 Annual Meeting Abstract, October 29, 2014, Austin, TX. Address correspondence and reprint requests to Gerard A. Baltazar D.O. , F.A. C.O. S. , Department of Surgery, St. Barnabas Hospital, 4422 Third Avenue, Bronx, NY 10457. E-mail: gbaltazar@sbhny.org. The authors have received no funds from any individuals or corporations for the production or to assist with the production of this research. The information provided below is presented without bias.