Clearance of the C-spine in the Unconscious Patient
Given that this is a common and practical ICU problem, the college have wisely included it among their SAQs - Question 10 from the second paper of 2008 asks the candidate to "Outline and justify your approach to “clearing” the cervical spine in an adult multi-trauma patient with a severe closed head injury".
Since this question (written in 2008),
- The Alfred published an evidence-based C-spine clearance protocol (2009)
- Another edition of Oh's Manual was produced, incorprating some new evidence (though still mostly referencing studies published prior to 2008).
- Patel et al published a set of guidelines: "Cervical Spine Collar Clearance in the Obtunded Adult Blunt Trauma Patient".
A synthesis of the abovelisted sources can be attempted, and rendered into this brief summary:
A normal result of a high-quality CT is enough to remove the collar.
Let us discuss this statement.
Clinical criteria for C-spine clearance basically exist to help you decide when you need to send the patient for a CT of the neck. Ch.78 from Oh's Manual (Spinal injuries by Sumesh Arora and Oliver J Flower) make specific mention of the NEXUS criteria and the Canadian C-spine rules. Even though everybody is already well aware of them, they are reproduced below largely as a reference for the forgetful author:
The NEXUS criteria
The C-spine CT is not required if there is :
• no posterior midline cervical spine tenderness
The Canadian Rules
The C-spine CT is not required if :
• The patient is under 65 years of age
• The mechanism was not "dangerous"
Sensitivity: 99.6% for significant injuries
Sensitivity: 100% for significant injuries
Flower and Arora reference this NEJM article from 2003 as a source for their discussion of the various C-spine rules. It is therefore probably worth reading. However, before the time-poor candidate commits themselves to a thorough exploration of the C-spine controversy, it would be important to mention that emergency departments routinely pan-scan their multitrauma patients, and the C-spine ends up getting caught in the radiation beam because "while you're there" and "that injury looks distracting" and "he's drunk and crazed with meth and we intubated him". So, for the intensivist, the question is rarely "does this patient need a CT", and frequently "when can we take the collar off".
To launch into the above-advertised thorough exploration of C-spine clearance rules, the NEXUS criteria are a good start. NEXUS stands for National Emergency X-Radiography Utilization Study, a prospective observational study of 34,069 patients published in NEJM by Hoffman et al (2000). The study tested the validity of five criteria for the exclusion of cervical spine injury: midline tenderness, altered mental state, intoxication, focal neurodeficit and distracting injury. These criteria were not explicitely defined; for example each participating centre was left to determine what constitutes a painful distracting injury. The NEXUS investigators then performed C-spine Xrays on all the patients. It turned out the NEXUS criteria were fairly sensitive. A radiologically apparent injury was missed only in 8 of the 818 patients who had significant C-spine trauma.
The Canadian rules are a slightly different set of criteria published by Stiell et al (2001). The authors prospectively observed 8924 patients. Instead of testing an already acknowledged list of criteria like the NEXUS authors, the Canadian group looked at 20 different clinical findings and compared their predictive value in excluding C-spine injury. By these rules, anybody with an age over 65, with a dangerous mechanism of injury, the presence of a sensory deficit or something preventing range of motion testing will get a CT by defauly. If you had a simple rear-end MVA, were sitting upright in the emergency department, were found ambulant at the scene of the accident, or had no neck pain - you could easily haveROM testing, and being able to actively and painlessly rotate the neck 45 degrees in either direction was 100% sensitive for the absence of a C-spine injury.
So which set of criteria is the better, or are they both the same? There appears to be only one direct comparison of NEXUS vs. Canadian rules (by the same guy who published the original Canadian rules paper - Ian Stiell et al, 2003). A 2012 review by Michaleff et al did not manage to find any others, but compared a whole series of data sets which validated a set of criteria independently. On their analysis, the authors found that the Canadian rules were slightly better. The sensitivity for both sets of rules was superb but the Canadian rules had a subtle advantage (the difference being 99.6% vs 100% sensitivity). Both sets of criteria have the distinct disadvantage of producing a lot of unnecessary imaging, but the Canadian rules are slightly less likely to cause inappropriate irradiation (they reduced imaging rates to 55.9%, as compared to 66.6% for the Nexus criteria). Given that we have these clinical criteria mainly because we do not want to scan everybody, a reduced imaging rate is an important performance characteristic.
Disadvantages of being in a C-spine collar
There are certain problems with being an immobile trauma victim trapped inside a stiff neck collar, with restrictions on how you can be turned for routine care, and how your torso can be positioned.
A 2004 review by Morris and McCoy (quoted in Oh's Manual) presents a list of disadvantages as Figure 1, which is summarised below with some modification:
Problems associated with prolonged C-spine immobilisation
None of these issues are going to sound surprising. Perhaps the reason these problems are neglected is that missed C-spine injuries are easy substrate for big public medicolegal spectacle, while a series of non-sexy complications like DVTs and bedsores are much less attractive to the media.
The Australian experience: when can we take the collar off?
According to a 2003 article, back then we didn't have a good standard way of doing this, and nobody was sure whether this was causing people harm. Lien Jaques and Powell lament:
"There is no standardised approach to the clearance of the cervical spine in intubated trauma patients in Australian intensive care units. In addition, morbidity from current practices and the true incidence of cervical spine injuries remains unknown."
So, in 2005 Cooper and Ackland published a summary which was good enough for the college to include on their website. In it, they discuss the evidence-based protocol they use at The Alfred. This cannot be a terrible protocol to follow, as it has been used as the source for at least one fellowship exam question. The specific feature of this is the simplicity of the algorithm they use for the unconscious patient. If the CT is normal, they clear the C-spine. Simple as that.
However, bold all-caps writing across their flowchart recommends that removing the collar in this context is a CONSULTANT-SUPPORTED DECISION, which I interpret as a warning. Any trainee clearing the C-spine from CT all by themselves will find themselves medicolegally exposed; more so if they aren't actually practicing at the Alfred. The reason for this is highlighted succinctly by the 2015 EAST guidelines: "the use of this approach may result in a nonzero rate of neurologic deterioration".
The implication, of course, is that in pursuit of a "zero rate" one ends up generating a nonzero rate of complications due to prolonged immobilisation, repeated scan transfers, unnecessary treatments and misguided specialist referrals.
The value of the trauma series CT in excluding spinal injury
- It picks up 97% of bony injuries
- It picks up 86% of subluxation injuries
- It misses 75% of ligamenous injuries
- It misses 100% (!!) of spinal cord injuries
However, a recent (2010) prospective study has concluded that for all its disadvantages, the CT picks up 99.75% of clinically significant spinal cord injuries. Yes, in other studies MRI found all sorts of extra ligamentous injuries whcih the CT had missed, but none of these were clinically significant, so why delay removing the collar?
When is it appropriate to use MRI to image the C-spine
There are a few features which would prompt you to order an MRI:
- Signs or symptoms of spinal cord injury
- The CT suggests there is ligamentous injury (or injury to the disc)
The reluctance of guideline-makers to greater integration of MRI into guidelines stems from the expense and poor availability of MRI, and from the risk of MRI transfer for the severely injured multi-trauma patient. Additionally, MRI can have a rate of false positives as high as 40%, resulting in the development of a large chronically C-collared population. If you are going to do it, then you should do it reasonably soon: after 72 hours, the gradual decrease in ligamentous oedema may increase the false-negative rate.
Is there any role for flexion-extension C-spine views
In this enlighetend age of iPhones and high-resolution helical CT scanners and whatnot, the humble flexion-extension C-spine film has fallen into disuse. So much has it become surpassed in diagnostic value, that some call for its immediate shamed expulsion from current C-spine management protocols. This view is supported by evidence. A 2013 systematic review of many heterogeneous studies has concluded that wherever CT and MRI are available, the value of this practice is minimal.