Glasgow Coma Scale

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Objective

The Glasgow Coma Scale (GCS) was first created by Graham Teasdale and Bryan Jennett in 1974. It is a clinical scale to assess a patient’s “depth and duration of impaired consciousness and coma” following an acute brain injury. Healthcare practitioners can monitor the motor responsiveness, verbal performance, and eye opening of the patient in the form of a simple chart. The GCS is the most commonly used tool internationally for this assessment and has been translated into 30 languages. It should not, however, be confused with the Glasgow Outcome Scale (GOS), which evaluates persistent disability after brain damage.

Method of Use

The GCS Assessment Aid has four steps to the assessment process: Check, observe, stimulate, rate.

The assessor should evaluate each of the subscales as listed in the Assessment Aid. Each subscale has several components (different quantity for each subscale). Based on what the patient is able to do on assessment, they are assigned a rating. The rating is matched with a score. A higher score indicates a greater level of consciousness.

Three sites for stimulation are used. These include finger tip pressure, trapezius pinch and supraorbital notch. When stimulating these areas, health care practitioners should look for one of two responses: an abnormal flexion response or a normal flexion response.

The National Institute for Health Care and Excellence (NICE) published clinical guidelines on Head injuries for assessment and early management. NICE recommends the following clinical guidelines:

• Until a patient has achieved a score of 15 on the GCS, patients should be observed every half hour.
• Once GCS score has reached 15, the patient should be re-assessed using the GCS every half hour for two consecutive hours.
• If the patient's GCS score remains above 15, the patient should be then observed once every hour for four hours and then every 2 hours after that.

Note: If a patient's’ GCS score drops below 15, the health care practitioners should revert to observing the patient every half hour.

The Institute of Neurological Sciences NHS Greater Glasgow and Clyde created a YouTube Video to demonstrate how to properly use the outcome measure.

Evidence

Reliability

The inter-rater reliabilty of the total Glasgow Coma Scale is p=0.86. Some research has subdivided the inter-rater reliabiltiy for each subscale. For the eye score the inter-rater reliability is p=0.76, the verbal score is p=0.67, and the motor score is p=0.81   The research for test-retest reliability is not recent and should be updated, however the best available evidence is k=0.66-0.77 

Validity

The validity of the glascow coma scale comes under fire because a lot of hospitals administer the test while patients have been sedated, often underestimating patient scores. It’s also difficult to elicit accurate scores when patients are intubated. Recent research has refuted that intubation elicits significantly different survival rates with the verbal score of r=0.90 and the total score r=0.97  The motor score is consistently the most predictive component of the GCS

Responsiveness

Given the current best available evidence, the GCS has a low sensitivity (56.1%) and a high specificity (82.2%). Therefore there are very few false positives predicting a low rate of survival in healthy individuals.

References

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