Fluid thresholds and outcome from severe brain injury.

OBJECTIVE: To determine, by retrospective analysis, critical thresholds for intracranial pressure, mean arterial pressure, cerebral perfusion pressure, and fluid balance associated with poor outcome in patients with severe brain injury.

DESIGN: Retrospective review of patient data from the prospective, randomized, multicenter National Acute Brain Injury Study: Hypothermia, comparing outcome results at 6 months after injury with intracranial pressure, mean arterial pressure, cerebral perfusion pressure, and fluid balance measurements recorded during the 96-hr period after randomization.

SETTING: Emergency departments and intensive care units in 11 metropolitan tertiary care university hospitals.

PATIENTS: A total of 392 patients, aged 16-65 yrs, with severe, nonpenetrating brain injuries and a Glasgow Coma Scale score of 3-8 after resuscitation, who were enrolled in a study designed to determine the treatment effect of moderate hypothermia in patients with severe brain injury.

INTERVENTION: Standard brain injury treatment for 193 randomly assigned patients and standard treatment plus hypothermia for 48 hrs for 199 patients.

MEASUREMENTS AND MAIN RESULTS: Intracranial pressure levels of 20, 25, and 30 mm Hg, mean arterial pressure levels of 70 and 80 mm Hg, cerebral perfusion pressure levels of 50, 60, and 70 mm Hg, and fluid balance levels in quartiles were examined for their effect on outcome as measured by the Glasgow Outcome Scale at 6 months after injury. When considered separately, any of the following-intracranial pressure >25 mm Hg, mean arterial pressure <70 mm Hg, or cerebral perfusion pressure <60 mm Hg and fluid balance lower than -594 mL-was associated with an increased percentage of patients with poor outcome. When the variables were combined into a stepwise logistic regression model, Glasgow Coma Scale score at admission, age, mean arterial pressure <70 mm Hg, fluid balance lower than -594 mL, and intracranial pressure > 25 mm Hg, in that order, were the most powerful variables in determining outcome.

CONCLUSIONS: Exceeding thresholds of intracranial pressure, mean arterial pressure, cerebral perfusion pressure, and fluid volume may be detrimental to severe brain injury outcome. Fluid balance lower than -594 mL was associated with an adverse effect on outcome, independent of its relationship to intracranial pressure, mean arterial pressure, or cerebral perfusion pressure.