VAGABOND: a Mnemonic to Aid in the Memory Retention of the Canadian CT Head Rule for Patients With Minor Head Injury: A Randomized Controlled Trial on Interns and Senior Medical Students

Introduction

Minor head injury is a serious public health problem. It is defined as a history of loss of consciousness, amnesia, or disorientation and a Glasgow Coma Scale (GCS) score of 13-15 [1]. Patients with minor head injury are frequently encountered in the emergency department and the outpatient settings [2]. In the United States, it is estimated that each year there are about 1.2 million Emergency Department (ED) visits and 800,000 visits to the outpatient setting related to minor head injury [2]. Although most patients with minor head injury can be discharged without sequelae after observation, a small proportion deteriorates and requires neurosurgical intervention for intracranial pathology [3]. Therefore, early diagnosis of such injuries by computed tomography (CT) followed by early surgery is very important in the treatment of those patients. Therefore, when faced with such situation, clinicians have to make the decision whether further investigation in the form of CT imaging of the head is necessary to rule out an intracranial lesion. Not imaging a minor head injury could potentially lead to significant consequences if an intracranial pathology is missed. On the other hand, imaging all patients will lead to unacceptable exposure to ionizing radiation and waste valuable health resources.

Clinical decision rules (CDRs) are tools that attempt to formally test, simplify, and increase the accuracy of clinicians' diagnostic and prognostic assessments. They guide clinicians, establish pretest probability, provide screening tests for common problems, and estimate risk [4]. A number of CDRs have been developed to guide clinicians dealing with minor head injuries on deciding whether CT scan of the head is indicated or not [1,5,6,7,8,9,10,11,12]. Among the multitude of CDRs, the Canadian CT Head Rule (CCHR) has been repeatedly shown to be useful with good sensitivity and specificity [13,14]. It was first developed and tested among 3212 patients with head injuries in 10 Canadian institutions between 1996 and 1999 and published in 2001[1].

The CCHR consists of five high-risk factors (failure to reach GCS of 15 within 2 h, suspected open skull fracture, any sign of basal skull fracture, vomiting ≥2 episodes, or age ≥65 years) and two additional medium-risk factors (amnesia before impact >30 min and dangerous mechanism of injury). The high-risk factors are 100% sensitive for predicting need for neurological intervention, and would require only 32% of patients to undergo CT. The medium-risk factors are 98·4% sensitive and 49·6% specific for predicting clinically important brain injury, and would require only 54% of patients to undergo CT [1].

Despite its demonstrated validity, awareness and use of the rule remains low in many parts of the developed world, including Canada [15]. In fact there is evidence that implementation of the rule did not lead to a reduction in emergency department use of CT imaging and in some occasions there was actually an increase over time in use of CT scans [16]. Several barriers of implementation have been suggested. One of these is physicians' forgetting the details of the rule at the bedside [17]. Having a simple mnemonic that acts as a memory aid to the different components of the rule may help overcome this barrier. Mnemonics have been shown to enhance retention of clinical decision rules such as the Ottawa Ankle and Foot Rules [18]. Therefore, this study proposes the hypothesis that a mnemonic to remember the CCHR will enhance retention of the components of this clinical decision rule by physicians and medical students.