Sunday, January 22, 2012

Canadian CT Head Rule

The Gist:  In a quest to identify patients with mild traumatic brain injury that need aggressive intervention, the Canadian CT Head Rule (CCHR) is more specific than the New Orleans Criteria (NOC).  Thus, utilizing this clinical decision tool may reduce the number of unnecessary CT scans without missing clinically important lesions that would benefit from neurosurgical intervention.

What is the Canadian CT Head Rule (CCHR)?   
Decision aid for use in Population:  GCS 13-15 with a witnessed loss of consciousness, confusion, or amnesia in mild head injury.  Recommends head CT if the patient has any of the following:
  • 2 episodes of vomiting
  • > 65 years old
  • Suspected open or depressed skull fracture
  • Sign of basilar skull fracture
    • Hemotympanum, mastoid process bruising (Battle's sign), CSF per nose or ears, raccoon eyes
  • Retrograde Amnesia to the Event > 30 minutes
  • "Dangerous" Mechanism
    • Pedestrian vs. motor vehicle
    • Occupant ejected from motor vehicle
    • Fall > 3 feet (from where your feet are) OR > 5 stairs
  • GCS < 15 at 2 hours after injury
How Good is the CCHR compared with other decision aids?
Validation studies Stiell et al, Smits et al, Papa et al demonstrate that the sensitivity of the CCHR is similar to the NOC, picking up lesions requiring intervention, but may miss lesions that wouldn't require intervention.  The CCHR is consistently more specific than the NOC.
  • Use of either depends on what the physician wants to know 
    • Which patients are going to need an intervention (use the CCHR) or 
    • Any abnormal imaging on CT (use NOC)
Papa et al validated the CCHR in a United States cohort (n=431)
  • Sensitivity: 100% for clinically significant injuries and injuries requiring neurosurgical intervention
  • Specificity:  28.2% (95% CI 24-33) for "clinically significant" and 66.7% (95% CI 62-71) for neurosurgical intervention
  • Limitations:
    • Single center study
    • Study did not affect physician practice in ordering CT.  i.e. the rule was great in retrospect but we'll need to see if it will actually change physician practice and be a clinically useful tool
    • Physicians were less comfortable with the CCHR than the NOC, perhaps because the GCS in patients was lower (which correlates with an elevated sphincter tone).  How well was CCHR really applied with this lower familiarity?
      • The CCHR is available on MDCALC, which may simplify the cognitive load of the tool

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