Application of the Canadian Computed Tomography Head Rule to Patients With Minimal Head Injury

Two clinical decision rules, the Canadian CT Head Rule and the New Orleans Criteria, set the standard to guide clinicians in determining which patients with minor head trauma need computed tomography (CT) imaging. Both rules were derived with patients with minor head injury who had had a loss of consciousness or witnessed disorientation. No evidence exists for evaluating patients and need for CT imaging with minimal head injury; that is, patients who had a head injury but no loss of consciousness or disorientation and therefore would have been excluded from the Canadian CT Head Rule and New Orleans Criteria trials. We evaluate the Canadian CT Head Rule in patients with head injury without loss of consciousness or witnessed disorientation (minimal head injury).

We studied a prospective convenience sample of patients with minimal head injury who received head CTs as part of their evaluations in the emergency department (ED). Participants were enrolled after head CT was ordered, but before the physician received the imaging results. Physicians were surveyed on their clinical reasoning for ordering imaging in this low-risk cohort of patients. Physicians surveyed consisted of ED attending physicians and senior-level emergency medicine residents. Final patient disposition was recorded when it became available. Patients with positive CT findings had their medical records reviewed for specific disposition, admission length of stay, ICU stay, and any operative or procedural interventions.

Two hundred forty patients with minimal head injury were enrolled. Five patients (2.1%) had head CTs that were positive for intracranial hemorrhage. All instances of intracranial hemorrhage occurred in patients who were at high or moderate risk by the Canadian CT Head Rule (2 high risk [age], 3 moderate risk [mechanism]). No patient with intracranial hemorrhage went to the ICU or underwent any intervention; the average hospital length of stay was 1.25 days. The Canadian CT Head Rule was 100% sensitive (95% confidence interval 40% to 100%) and 29% specific (95% confidence interval 23% to 35%) for the presence of intracranial hemorrhage. Physicians listed their own reassurance (24.6%), patient reassurance (24.2%), patient expectation (14.6%), and reduction of legal liability (11.7%) as the rationale for ordering head CT in patients with minimal head injury. Shared decisionmaking was used in 51% of cases.

Risk of intracranial hemorrhage in patients with minimal head injury was very low, and even in patients found to have an intracranial hemorrhage, none had any serious adverse outcome (eg, death, intubation, prolonged hospitalization, surgical procedure). The Canadian CT Head Rule was 100% sensitive in this small cohort of patients with minimal head injury. Among our study cohort, which specifically included only patients who had CT scanning, applying the Canadian CT Head Rule may have reduced the need for CT, potentially saving costs and resources. However, because many patients with minimal head injury who present to the ED may not have CTs, it is unclear what effect the broad application of this rule would have on overall CT use. Providers' rationale for obtaining CT was multifactorial. These represent barriers that may need to be overcome before physicians are comfortable changing CT ordering patterns in this group of head injury patients.