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Intracranial pressure independently predicts mortality, short-term outcomes, demonstrates association with Marshall CT score in patients with severe TBI, study shows

Monday, October 20 2008 | Comments

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What's This? There is a significant relationship between the level of intracranial pressure (ICP), mortality, and 6-month outcomes in patients with severe traumatic brain injury (TBI), a retrospective study indicates.

Moreover, there is a correlation between Marshall computerized tomography (CT) classifications and ICP "dose," providing evidence in favor of using the Marshall system to assess TBI.

The Norwegian study included 93 patients (median age, 34 years; 81% male) who underwent ICP monitoring for TBI between 1998 and 2002. The primary goal of the study was to compute the ICP dose as the cumulative area under the curve (AUC) above a target goal of 20 mm Hg and to correlate the results with patient outcomes. A secondary goal was to compare the ICP dose with the Marshall CT score, which has been linked with the development of ICP.

Patients were included in the study if they had a Glasgow Coma Scale (GCS) score of <=8 before sedation and intubation or at a later time. Those with a GSC score of >8 before intubation also were included if their pupils were dilated and their CT scans were deteriorating. CT scans confirmed TBI in all cases. GCS scores exceeded 8 before intubation but deteriorated to <=8 in 5 patients. Pupillary abnormalities were present in 31% of the patients on admission.

In addition to an ICP goal of <=20 mm Hg, the target cerebral perfusion pressure was >=60 mm Hg to 70 mm Hg. The median time before ICP monitoring was initiated was 9 hours (range, 3-66 hrs), and the median monitoring time was 10 days.

ICP values exceeded 20 mm Hg in 60 patients (65%). Of these, 12 patients (13%) died as a result of severe intracranial hypertension with subsequent cerebral herniation.

After adjusting for GCS score, papillary abnormalities, age, and Injury Severity Scale scores, ICP AUC was determined to be a significant predictor of death (P=.035) and poor 6-month outcomes (P=.034), but it was not a significant predictor of long-term outcome (based on median follow-up of 62 months; P=.157).

Significantly higher ICP AUC values were observed in the 24 patients who were classified with CT-measured Marshall head injury categories 3 and 4 than in the 23 patients classified as category 2 (P=.025) or in the 46 patients classified as category 5 (P=.021).

This study demonstrates a significant relationship between ICP dose and mortality and 6-month outcomes, as well as between ICP dose and the patients' worst Marshall CT scores, according to the researchers, lending support to the use of the AUC method to classify TBI. The method may also be a valuable means of refining treatment of ICP in patients with TBI, they said, but prospective studies using 1-minute high-frequency measurements are necessary to further determine its utility. (Vik A, et al. J Neurosurg 2008;109:678-684.)

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