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An IMPACT Analysis of the Prognostic Value of the Glasgow Coma Scale

Review of: Marmarou A, Lu J, Butcher I, et al: "Prognostic value of the Glasgow Coma Scale and pupil reactivity in traumatic brain injury assessed pre-hospital and on enrollment: An IMPACT analysis." Journal of Neurotrauma. 24(2):270-80, 2007.

The Science

IMPACT is an acronym for "International Mission for Prognosis and Clinical Trial," a database of traumatic brain injuries. This massive database has been in existence for several years and is used by researchers to find various trends related to traumatic brain injury that can be used to predict patient outcome. This specific study is an analysis of the value of the Glasgow Coma Scale (GCS) in combination with papillary reactivity to predict the severity of brain injury.

The authors found a statistical correlation between lower GCS and worse outcome. While this may not come as a surprise, further review of their data shows that the motor component in combination with pupil response to light is the most sensitive. However, the researchers concluded that the prehospital GCS should not be used as the starting point for prognostic tracking, because it is unreliable and usually falsely lower than the GCS and pupil response obtained at the hospital.

The Street

First, I must admit my bias. I have never seen the value of EMS obtaining a GCS on a patient. Studies have shown that it is unreliable for many reasons. The primary one is that we don't perform it correctly. We assess level of consciousness using AVPU. This scale has four outcomes-Alert, Voice, Pain, Unresponsive. It is much more objective and helps us appreciate the potential for the patient losing their airway, which is after all the most important prehospital issue for all patients.

Admit it. When was the last time you pulled out a GCS chart and went step by step through it and assigned a number? Is your definition of withdraws from pain the same as your partner's, or do they call it posturing? If the patient is unconscious from a head injury, even a mild concussion, their verbal score is going to be artificially low. We arrive at the scene so soon after the injury that our patients are just waking up, and their neurological status fluctuates wildly.

The American College of Surgeons has placed the GCS score at the top of the list of findings to be used to determine the needs for transporting the patient to a Level One center. However, in EMS, we use other more gross measures of severity to determine where patients should go.

This paper supports my contention that EMS should abandon the GCS. It only has value once the patient reaches the hospital and is obtained in a reliably systematic manner. The fact that the motor score is the best predictor when combined with pupil response further indicates the weaknesses of obtaining the GCS in the field.

We need to find a way to translate the GCS into its AVPU equivalents, so that the assessments we perform in the field provide both us and those that care for our patient the most important, relevant and useful information.


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