Relationship of "dose" of intracranial hypertension to outcome in severe traumatic brain injury.

Object: It has recently been suggested that the degree of intracranial pressure (ICP) above the treatment goal can be estimated by the area under the curve (AUC) of ICP versus time in patients with severe traumatic brain injury (TBI). The objective of this study was to determine whether the calculated "ICP dose"-the ICP AUC-is related to mortality rate, outcome, and Marshall CT classification.

Methods: Of 135 patients (age range 1-82 years) with severe TBI treated during a 5-year period at the authors' institution, 113 patients underwent ICP monitoring (84%). Ninety-three patients with a monitoring time>24 hours were included for analysis of ICP AUC calculated using the trapezoidal method. Computed tomography scans were assessed according to the Marshall TBI classification. Patients with Glasgow Outcome Scale scores at 6 months and >3 years were separated into 2 groups based on outcome.

Results: Sixty patients (65%) had ICP values>20 mm Hg, and 12 (13%) developed severe intracranial hypertension and died secondary to herniation. A multiple regression analysis adjusting for Glasgow Coma Scale score, age, pupillary abnormalities and Injury Severity Scale score demonstrated that the ICP AUC was a significant predictor of poor outcome at 6 months (p=0.034) and of death (p=0.035). However, it did not predict long-term outcome (p=0.157). The ICP AUC was significantly higher in patients with Marshall head injury Categories 3 and 4 (24 patients) than in those with Category 2 (23 patients, p=0.025) and Category 5 (46 patients, p=0.021) TBIs using the worst CT scan obtained.

Conclusions: The authors found a significant relationship between the dose of ICP, the worst Marshall CT score, and patient outcome, suggesting that the AUC method may be useful in refining and improving the treatment of ICP in patients with TBI.