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26-04-2012 | Surgery | Article

Clinical scales poor guide to acute brain injury management


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MedWire News: Current clinical and radiographic scales poorly predict the acute clinical course of patients with traumatic brain injury (TBI), report researchers.

The only scale that provided any information on acute clinical course was the Acute Physiology and Chronic Health Evaluation (APACHE) II scale, which was associated with brain tissue oxygen tension (PbtO2) but not with intracranial pressure (ICP).

Peter le Roux (University of Pennsylvania Medical Center, Philadelphia, USA) and co-workers studied 101 patients (median age 41 years) who had traumatic brain injury, a Glasgow Coma Scale (GCS) score of 8 or less on admission or shortly afterward, and data on intracranial physiologic values. The median admission GCS score was 3.0.

In contrast with the APACHE II score, the other scores that the team evaluated - the GCS and the Injury Severity Score (ISS), and the Marshall and Rotterdam radiographic scores - were not associated with subsequent brain physiologic abnormalities. Furthermore, the ISS and the GCS did not predict mortality, despite widespread use of the GCS to classify TBI and to determine whether patients should receive an ICP monitor.

After accounting for multiple confounders, patients' admission APACHE II scores (with or without the GCS) were inversely associated with their minimum PbtO2 in the intensive care unit and with the amount of time spent below specific PbtO2 thresholds.

"Our results suggest that this, ie, an understanding of the full physiological impact of the injury (APACHE), rather than how it affects brain function alone (eg, GCS or [computed tomography] score), may better predict brain oxygenation over time," the researchers write in Neurosurgery.

They add: "This finding emphasizes that it is important to differentiate between the concepts of prognostic factors and factors that relate to a patient's ICU course and potential to benefit from an intervention."

Older age was associated with lower median and maximum ICP, and women had higher minimum PbtO2 than men.

In all, 37.6% of patients died and 51.5% had a favorable outcome (no more than moderate disability on the Glasgow Outcome Scale). Despite current recommendations for ICP monitoring in severe TBI patients, ICP was not associated with outcomes, with median ICPs of 15 mmHg in patients who died and 14 mmHg in survivors.

By contrast, median PbtO2 was significantly lower in patients who died than in survivors, at 27.6 versus 32.4 mmHg, and minimum PbtO2 and time spent below specific PbtO2 thresholds were associated with mortality. Most PbtO2 measures were also associated with favorable outcomes.

"We suggest that when an ICP monitor is to be placed, a PbtO2 monitor also should be placed regardless of the initial clinical and radiological admission scores," conclude le Roux et al.

By Eleanor McDermid

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