What Canada Can Teach Us About CAT Scans

Joe Habbousche is the CEO of MDCalc, the world's most used online medical calculator. Chances are, you've used it yourself. Joe is a passionate advocate for the practice of evidence based medicine and the proper use of clinical decision tools. In this episode, we dissect one of his favorites: the Canadian CT Head Injury/Trauma Rule   Canadian CT Head Injury Rule Derived and validated in a large patient population Overall 8% of patients had positive CTs, but only 1.5% required intervention   Two sets of criteria High Risk/Major Criteria Designed to capture patients that went on to require intervention. Medium Risk/Minor Criteria Added on to the high risk criteria to capture those with clinically important brain injury- CT findings that require admission or observation   Who does this not apply to? Patients on blood thinners/bleeding disorder Under 16 years old Seizure after trauma No clear history of trauma Obvious penetrating skull injury or obvious depressed fracture Acute focal neurological deficit Unstable vital signs associated with major trauma Returned for reassessment of the same head injury This is a one directional rule Designed to be sensitive but not necessarily specific This decision rule was designed because when CT imaging is done in all comers with head injury, it has very low yield The CT Head Injury/Trauma rule asks, "Can I carve out a cohort of patients who we know will not have a need for this test." If you fall in this group (the cohort that the rule says doesn't need the test), then you don't need the test Here's the one directional part: If you fall outside that group, the group the rule says does not need the test....the rule DOES NOT COMMENT. It is not studying anyone outside the group that has been deemed safe to not have the test done   Canadian CT Head Rule Applies to this group of patients Blunt trauma to the head resulting in witnessed loss of consciousness Definite amnesia or witnessed disorientation Initial emergency department  GCS score of 13 or greater as determined by the treating physician Injury within the past 24 h   High Risk Criteria: Rules out need for neurosurgical intervention Fails rule with any of the following GCS

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