Source: DGNews  |  Posted 2 years ago

By Kristina Rebelo

SAN DIEGO -- May 8, 2009 -- Glutamate levels measured by microdialysis are correlated with the mortality rate and 6-month function outcome in cases of traumatic brain injury (TBI), according to new data presented here at the 77th Annual Meeting of the American Association of Neurological Surgeons (AANS).

In this prospective study, undertaken at the Ben Taub General Hospital, Houston, Texas, researchers examined glutamate levels via cerebral microdialysis in patients with severe TBI, to investigate and then analyse any prognostic values.

"We wanted to know if there was efficacy in antiglutamate therapy, and if it would be beneficial for a subgroup," said Roukoz B. Chamoun, MD, Baylor College of Medicine, Houston, Texas, speaking here on May 4.

The study involved 165 patients with severe TBI who had a total Glasgow Coma Score of 8 or less within 48 hours of injury. All patients were treated according to a standard protocol. Management included surgery when indicated and invasive monitoring, including intracranial pressure and brain tissue oxygenation, demographic data, findings from computed-tomography scans, and 6-month follow-up outcomes.

The study revealed that initial high glutamate values were found to be predictive of a poor outcome. The mortality rate, for example was 30.3% in patients with a glutamate level of more than 20 versus 18% in patients with a glutamate level of less than 20.

Multiple patterns of changes in glutamate levels over time were identified, and had different prognostic values, noted Dr. Chamoun. In the final analysis, 2 general patterns were recognised. Pattern 1 demonstrated that glutamate levels tended to normalise over the monitoring period (120 hours). Pattern 2 demonstrated that glutamate levels tended to increase with time or remain abnormally elevated.

Patients exhibiting pattern 1 had a lower mortality rate (17.1% vs 39.6%) and a better 6-month functional outcome among survivors (41.2% vs 20.7%).

"Although there was a clear trend toward significance and a potential clinical impact, we did not reach statistical significance here," Dr. Chamoun hastened to add, "however, glutamate levels and patterns measured by microdialysis do appear to have an important role in TBI, as suggested by these data. The results of this research yielded several interesting clinical aspects, which warrant additional studies."

Session moderator Geoffrey T. Manley, MD, PhD, University of California, San Francisco, and San Francisco General Hospital, San Francisco, California, followed up by commenting that Dr. Chamoun's study added to the TBI body of knowledge.

"This speaks to targeted therapy in the future," he said.

[Presentation title: The Role of Extracellular Glutamate Measured by Cerebral Microdialysis in Severe Traumatic Brain Injury. Abstract 646]