Whenever my colleagues or nurses ask me what GCS a patient has, I just make something up that sounds about right. Judging by their smirks I know they think that they know I didn’t check properly. The truth is far worse. I don’t know the Glasgow Coma Scale.
Despite med school and my 10 years as a doctor having worked thousands of patients where the GCS is relevant I still haven’t managed to learn the damn thing. I guess it in so many ways never made sense to me, and furthermore I can’t think of one single instance where it affected my clinical decision-making.
So I’m delighted every time I run into someone who also thinks the GCS is rubbish and has no place in emergency medicine. Maybe I have a friend in one Dr Steven Green. He wrote a great editorial in a recent issue of Annals of Emergency Medicine that outlines the problems with the Glasgow Coma Scale.
Below are some of the things he touches on. I have linked to some of his references.
It was never intended for use in trauma or emergency medicine
When Teasdale and Jennet invented the GCS back in 1974 it was designed as a tool for repeated bedside assessment of various neurological functions in patients in a neurosurgical ward. It was never intended to be used as tool in trauma or emergency medicine. And it was most definitely not supposed to be used the way we use it. The sub scales were never meant to added up to a total score.
The inventors even publicly disowned the GCS in the form we know it . Back in 1978 they wrote ‘We have never recommended using the GCS alone, either as a means of monitoring coma, or to assess the severity of brain damage or predict outcome.’
It is not as reliable or precise as you think
For the GCS to work as intended it needs give reproducible results that allows reliable monitoring over time and allows for being communicated between professionals. It does not.
One study compared GCS assessments between pairs of emergency physiscians. Only in 38% of the cases the GCS scores were the same and in 33% of cases the scores varied with more than two points. The precision of the GCS is greatly overstated.
Because of it’s seemingly high level of detail it gives us a false impression of having created order out of chaos. It is a numeric illusion.
The subscales aren’t comparable and don’t add up
The GCS tells us to sum up the scores from the three different scales (motor, vocal, pain). That implies that the three scales are somehow interrelated and furthermore have the same clinical magnitude. It should be obvious to anyone that that is highly unlikely.
A most glaring example, is how the same GCS can predict different mortality depending on the inherit components. Studies have compared mortality with variation in subscale scores that result in the same GCS. This is a good illustration of the futility of adding the subscale scores
A GCS of 4 with the components 1+1+2 (E+V+M) predicts a mortality rate of 48%. But if we calculate the same GCS of 4 with the components 1+1+2 it will suddenly predict a mortality rate of 27%.
This is another aspect to which the authors objected in vain.
The GCS is not consistently teached or remembered
Due to its complexity and the way it is defined the GCS is hard to teach consistently and even harder to remember. When tested on the GCS even neurosurgeons get it right only 56% of the time. Military physicians calculate the GCS correctly only 15% of the time.
It doesn’t really do anything for you.
The GCS does not reliably predict brain injury, need for intervention or prognosis. There is actually no evidence it yields any benefit above unstructured assessment.
Here you might argue that ‘it does, it really does, it helps me decide when, for example, to intubate a patient or not‘.
Does it really? When was the last time you intubated a patient as a result of a calculated GCS? We (me and my man Dr Green) thought so. You intubated as a result of a fuzzy, unstructured assessment and at best used a retrocalculated GCS to vindicate that decision.
Simpler scales perform just as well
Studies show that using any of the GCS subscales or other scales such as the AVPU work just as well.
Read the editorial here. Dr Green named his editorial
‘Cheerio, Laddie! Bidding Farewell to the Glasgow Coma Scale’
I find the title a bit weak and ambiguous. Wavering even. What is he trying to tell us? What is his message? Is he pro- or con-GCS?