It’s funny, I would have expected that the more I advance my career and knowledge, the more advanced the topics that I learn would be. It turns out, though, that the more experience I get, the more I realize that a lot of what I learn is simply a matter of getting better at the basics. So on that note, let’s do a deeper than normal dive into the Glasgow Coma Scale this week, not the “how to” BS we already know, but the “why even?”
GCS: It May Not Mean What You Think It Means, And Even If It Does, We Suck At It Anyways
It doesn’t get more basic than the good ol’ Glasgow Coma Scale that you were taught as a rookie EMT. It’s part of every report, for every patient, because everyone said it’s that important! So, what is it, what does it mean, and how should we use it?
GCS started as a scale specifically for trauma patients. I know we usually think of the GCS for medical patients and the Revised Trauma Score for trauma patients, but that’s not the case. In 1974 Dr. Graham Teasdale published his Glasgow Coma Scale in the Lancet as a way to neurologically assess, specifically, traumatic brain injury patients. Over the years, and with it’s fair share of critics, this assessment has slowly crept into broad use for all patients, including medical and prehospital patients.
So why does the history lesson matter? The problem is we often make very serious clinical decisions based solely on this number, even though, when used in these other patient populations, we are unknowingly making several (inaccurate) assumptions. Dr Green wrote this in 2011:
In 1978, the creators of the GCS said, “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.” Nevertheless, clinicians worldwide persist in using the GCS for all of these things—now despite compelling contrary evidence. The GCS should be abandoned in the ED and out-of-hospital settings altogether.
Why don’t you tell us what you really think, Dr Green.
To start with what you may already know, deep in the cockles of your sleep deprived soul, we cannot accurately use GCS as an independent rating of the severity of the patient. (See the article above) What if I give you 2 patients, one with a GCS of 3, and one with a GCS of 12? What assumptions do you make comparing them? What if I told you the first was a unresponsive hypoglycemic patient (3), while the second is a motorcycle wreck with inappropriate speech and who doesn’t follow commands. (12) Here is an article in the Lancet that reviews it’s use and accuracy 40 years later. My personal summary: the GCS score itself doesn’t mean much, but describing each category result, especially motor, along with an actual patient assessment does, and the motor score may be a better predictor than the GCS itself.
Which brings us to our second assumption: that the number is even accurate in the first place. Dr. Green found 1 in 3 patients were scored inaccurately. Dr Bledsoe found that we are only relatively good at three scores: 3, 14, and 15; the rest are a crap shoot. We’re talking about an overall accuracy of 33%. Yeah, that’s bad.
Additionally, GCS is a system designed to assess neurological status. That means that the moment the neurological status of the patient has been artificially altered, such as with sedation, the GCS doesn’t change, it is now unable to be scored. I feel like I should have been taught that much sooner in my career.
So, GCS isn’t objectively accurate, we suck at doing it, and we don’t know when it applies to our patients; sounds like we should be paralizing patients based soley on it’s relation to the number 8, right!?!?!
GCS 8, Intubate!
Ok, ok, I hear you. You are absolutely, one hundred percent positive about your scores. Your patient with a GCS of 9 that just dropped to an 8… you’ve got to intubate now, right? The risk of aspiration! More assumption time.
We assume that something changes at 8. Suddenly the patient cannot maintain their own airway. There are quite a few articles that indicate we should do away with this mentality. Here is a fun one that, although small, looked at intoxicated patients with a GCS from 3-14. The results? None of the patient with a GCS of 8 or less aspirated despite not being intubated. Only one patient needed intubation, and they had a GCS of 12. Here is another, who’s conclusion was:
reduced GCS is significantly related to gag and cough reflexes. However, a considerable proportion of patients with a GCS≤8 have intact airway reflexes and may be capable of maintaining their own airway, whilst many patients with a GCS>8 have impaired airway reflexes and may be at risk of aspiration. This has important implications for airway manage
Clearly there needs to be more to the decision than their GCS. Yes, there is absolutely a correlation between GCS and abnormal gag reflex; a GCS of 3 has a higher risk of aspiration than a GCS of 15. That’s common sense, but here are the numbers if you need them. (My favorite number from the article, 22% of the patients with a GCS of 15 had abnormal gag reflexes! Whaaaaa?) What the facts show is that RSI has risks, and assuming clinical course based off of an inaccurate correlation may not be in the patients best interest. Gag and cough reflex is key, not the GCS.
So what have I learned this week?
We all suck at GCS, but the good news is it doesn’t mean as much as I thought…
but maybe the motor score does…
but maybe not because we use it wrong anyways, like documenting one after we sedate and paralyze…
but when we do it right we use it to treat airways wrong…
Momma was wrong…