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We'll have several different sections reporting in - recent research, local topics, or highlighting areas of the Sponsor Hospital Council of Greater Bridgeport protocols.

*** Keep in mind - this website does not replace your protocols, and these posts do not reflect SHCGB or Bridgeport Hospital policies. This is a place to discuss research, controversies, or discuss possible future protocols. When in doubt, check your current protocols through the official source.

Monday, January 14, 2013

Can you "GLASS" the patient to clear the c-spine?

It's hard to know what to write about, since there are so many valuable new studies being published each week. How can I choose?

Not filed under "valuable new studies": Leg-compression CPR

I just wrote about EMS and cervical spine trauma. However, a new study deserves attention for a few important reasons.

First, it describes a simple method of assessment.  Second, it "fits" with common sense

Lastly, one of the co-authors is a Bridgeport Hospital ER doc!

Dr Althoff (Note: does not usually dress like the Unabomber at work)
"Clearing" the spine by EMS
 There has been a lot of discussion about how to "clear" the potential cervical-spine injury in the field. Some people like the simplicity of the NEXUS criteria, while other think that the Canadian C-Spine Rule (CCR) is more sensitive, and thus safer

The use of these rules, though, can get complicated and confusing, with people arguing over how to define "intoxication" (when using NEXUS), or what is a "dangerous mechanism" (when using the CCR). Also, if the patient describes paresthesias, or insists that their neck is tender, despite an exceedingly minor mechanism, you may be obligated to immobilize.

Researchers at the University of Virginia decided to try a different approach - instead of examining the patient who has been in a MVC, how about just examining the car?

The stupidest clip-art I could find with Google Image

The "Glass Intact Assure Safe Cervical Spine Protocol" study
The researchers used a national database of MVCs that had been reported to police, where at least one of the vehicles had been towed from the scene. The vehicle had all received a complete, systematic survey for damage afterwards by the NASS investigators, using both crash-scene photos and reports collected by police, as well as direct inspection of the vehicles. In addition, federal researchers combed over medical records to determine whatever injuries the occupants had suffered.

The Virginia researchers then looked at a subset of the patients in the national database:
  • Ages 16-60,
  • Had been wearing setbelt,
  • Airbags did not deploy, 
  • All the car windows were intact
They called these the "GLass intact Assures Safe Spine," or GLASS, criteria. They then looked at how many "GLASS-negative" patients were subsequently found to have an unstable cervical spine fracture after the MVC. 

Well, it wasn't many. Out of 7639 drivers or passengers who met the "GLASS" criteria, only 6 had an unstable cervical spine fracture - that's 0.008%. Really, really infrequent.

Is this protocol ready to use?
Not quite yet, but it's promising. 

Keep in mind that this used a retrospective design, and a prospective design might look better or worse. And although there were very few injuries, they were serious. Here's a breakdown of those few, unlucky, patients with a spine injury after their minor (to us) MVC:

It's tough to draw any conclusions about these "potentially-missed" neck injuries You might be tempted to pay special attention to middle-aged females, but the (very, very) small sample really doesn't let us conclude much.

Nonetheless, the negative predictive value (or NPV) is astoundingly reassuring, with a confidence interval 99.86% to 99.98%. That's about identical to the NEXUS rule-out criteria, and much better than many other rules in emergency medicine (e.g. the PERC rule). 

Perhaps the biggest strength of the study is the number of MVCs studied. There is no way that the Virginia researchers could have investigated 14,000 MVCs on their own. Although you always have to worry about the quality of any one individual data-point in such studies, the mass of data enables us to identify important effects that would not be identified in smaller (although supposedly more high-quality) studies. 

The Bottom Line
The next time you pull up to an MVC, and you see all the car windows intact, you can check the results for yourself.

But you still better go ahead and talk to the patient and do a physical exam! 

Questions for one of the authors?
I've talked with Dr Althoff about this study on a number of occasions, EMS spinal care in general, and also future directions for research in this area. If you have questions about this study, or a related topic, send in a comment!