I was watching a TED talk the other day and heard an interesting quote. Anil Seth, who was discussing consciousness stated: "Anesthesia -- it's a modern kind of magic. It turns people into objects, and then, we hope, back again into people." This statement got me thinking about levels of consciousness and how we quantitate it as clinicians.
Prior to the mid 1970's it was very difficult for clinicians to not only agree on a definition of consciousness, but also the nomenclature that would follow. Because of this lack of universal language regarding consciousness, there were often delays in detecting neurological changes. This led to the proposal of a universal scale to assess levels of consciousness in comatose and consciously impaired individuals. In 1974 the Lancet published an article titled " Assessment Of Coma and Impaired Consciousness."
This scale was launched from a neurosurgical unit in Glasgow, UK. "This process was applied not only to head injuries but also to other acute brain disorders, such as stroke, and especially subarachnoid hemorrhage. The need for clear, consistent clinical communication between local hospitals and specialist units was a major stimulus to develop the scale" (Teasdale, 2014). It is obvious that the Glasgow Coma Scale (GCS) is not designed classifying levels of anesthesia, when you analyze its criteria.
I have yet to see someone develop decerebrate posturing after giving a dose of midazolam to an anxious patient in flight. It also appears wrong to qualify levels of sedation based off pain response when sedation is intentionally administered. When a scale, score, or criteria is adopted it must be utilized for its intended purpose. It is all too often that we see scores or criteria extrapolated out of context from its original purpose to satisfy another.
When we evaluate GCS criteria in the absence of pathological neuro changes (TBI, CVA, Etc.)
1. Does not suggest an intervention. (No, less than 8 does not always mean intubate.)
2. Distorts or generalizes communication of actual level of sedation.
3. Allows little room to detect changes.
So what should we use to evaluate sedation?
Clarity and ease of use is arguably the reason the GCS became adopted so readily. However when we monitor levels of agitation or finer points of sedation, we find descriptive limitations using the GCS. Anesthesiologist commonly utilize the Richmond-Agitation-Sedation Scale (RASS).
If you imagine zero is where you are now (alert and calm... hopefully), any escalations from zero would be increasing agitation. The additive formulary to calculate a GCS paints a very vague picture of the patient. Additionally, rating someone a "one" for motor function just because they won't "obey your command," seems inaccurate in context to the original purpose of the scale. My kids are notoriously a one in this category.
Ok, so we get that it is not ideal for measuring or relaying agitation information, but what about sedation? If we state in a report that we increased the patients propofol infusion because of "increased agitation," it would make sense to describe their arousal as clear as possible. Aiming for "unarousable" is not without its own negative sequelae. There is increasing evidence that deep sedation, particularly with benzodiazepines, leads to increase rates of delirium throughout an individuals hospital course and mortality (Pandharipandi, 2006).
The argument for deep sedation in transport is often prefaced with the austere and noxious stimuli environment of an ambulance or helicopter. However, we may benefit from targeting a RASS -3 or -4 with simple modifications of adding ear-muffs or blind-folds to reduce the amount of exogenous medically induced sedation required.
Just by reading this last paragraph and comparing the RASS score I provided, you are able to deduce a mental image of what this patients sedation may look like. This is one of the benefits of a single value sedation scale. One does not need to concern with accounting for the values of each criteria that are then added up to represent a sum, as such is needed when communicating a GCS.
It is easy to aim for deep sedation and slug paralytics... and sometimes it is therapeutically necessary. However, it may be time that even in the transport environment, we tighten up our evaluation of sedation, look at additional means to reduce noxious stimuli, and hopefully prevent the need for deeper levels of sedation.
Lorazepam is an independent risk factor for transitioning to delirium in intensive care unit patients.
The Glasgow Coma Scale at 40 Years: standing the test of time.
The Internet Book of Critical Care (IBCC)
The Richmond Agitation-Sedation Scale: validity and reliability in adult intensive care unit patients.