Mary A. Eisenhauer

The Canadian CT Head Rule for patients with minor head injury

BACKGROUND There is much controversy about the use of computed tomography (CT) for patients with minor head injury. We aimed to develop a highly sensitive clinical decision rule for use of CT in patients with minor head injuries. METHODS We carried out this prospective cohort study in the emergency departments of ten large Canadian hospitals and included consecutive adults who presented with a Glasgow Coma Scale (GCS) score of 13-15 after head injury. We did standardised clinical assessments before the CT scan. The main outcome measures were need for neurological intervention and clinically important brain injury on CT. FINDINGS The 3121 patients had the following characteristics: mean age 38.7 years); GCS scores of 13 (3.5%), 14 (16.7%), 15 (79.8%); 8% had clinically important brain injury; and 1% required neurological intervention. We derived a CT head rule which 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 were 100% sensitive (95% CI 92-100%) for predicting need for neurological intervention, and would require only 32% of patients to undergo CT. The medium-risk factors were 98.4% sensitive (95% CI 96-99%) and 49.6% specific for predicting clinically important brain injury, and would require only 54% of patients to undergo CT. INTERPRETATION We have developed the Canadian CT Head Rule, a highly sensitive decision rule for use of CT. This rule has the potential to significantly standardise and improve the emergency management of patients with minor head injury.

Sensitivity of computed tomography performed within six hours of onset of headache for diagnosis of subarachnoid haemorrhage: prospective cohort study

Objective To measure the sensitivity of modern third generation computed tomography in emergency patients being evaluated for possible subarachnoid haemorrhage, especially when carried out within six hours of headache onset. Design Prospective cohort study. Setting 11 tertiary care emergency departments across Canada, 2000-9. Participants Neurologically intact adults with a new acute headache peaking in intensity within one hour of onset in whom a computed tomography was ordered by the treating physician to rule out subarachnoid haemorrhage. Main outcome measures Subarachnoid haemorrhage was defined by any of subarachnoid blood on computed tomography, xanthochromia in cerebrospinal fluid, or any red blood cells in final tube of cerebrospinal fluid collected with positive results on cerebral angiography. Results Of the 3132 patients enrolled (mean age 45.1, 2571 (82.1%) with worst headache ever), 240 had subarachnoid haemorrhage (7.7%). The sensitivity of computed tomography overall for subarachnoid haemorrhage was 92.9% (95% confidence interval 89.0% to 95.5%), the specificity was 100% (99.9% to 100%), the negative predictive value was 99.4% (99.1% to 99.6%), and the positive predictive value was 100% (98.3% to 100%). For the 953 patients scanned within six hours of headache onset, all 121 patients with subarachnoid haemorrhage were identified by computed tomography, yielding a sensitivity of 100% (97.0% to 100.0%), specificity of 100% (99.5% to 100%), negative predictive value of 100% (99.5% to 100%), and positive predictive value of 100% (96.9% to 100%). Conclusion Modern third generation computed tomography is extremely sensitive in identifying subarachnoid haemorrhage when it is carried out within six hours of headache onset and interpreted by a qualified radiologist.

Implementation of the Canadian C-Spine Rule: prospective 12 centre cluster randomised trial

Objective To evaluate the effectiveness of an active strategy to implement the validated Canadian C-Spine Rule into multiple emergency departments. Design Matched pair cluster randomised trial. Setting University and community emergency departments in Canada. Participants 11 824 alert and stable adults presenting with blunt trauma to the head or neck at one of 12 hospitals. Interventions Six hospitals were randomly allocated to the intervention and six to the control. At the intervention sites, active strategies were used to implement the Canadian C-Spine Rule, including education, policy, and real time reminders on radiology requisitions. No specific intervention was introduced to alter the behaviour of doctors requesting cervical spine imaging at the control sites. Main outcome measure Diagnostic imaging rate of the cervical spine during two 12 month before and after periods. Results Patients were balanced between control and intervention sites. From the before to the after periods, the intervention group showed a relative reduction in cervical spine imaging of 12.8% (95% confidence interval 9% to 16%; 61.7% v 53.3%; P=0.01) and the control group a relative increase of 12.5% (7% to 18%; 52.8% v 58.9%; P=0.03). These changes were significant when both groups were compared (P<0.001). No fractures were missed and no adverse outcomes occurred. Conclusions Implementation of the Canadian C-Spine Rule led to a significant decrease in imaging without injuries being missed or patient morbidity. Final imaging rates were much lower at intervention sites than at most US hospitals. Widespread implementation of this rule could lead to reduced healthcare costs and more efficient patient flow in busy emergency departments worldwide. Trial registration Clinical trials NCT00290875.

High risk clinical characteristics for subarachnoid haemorrhage in patients with acute headache: prospective cohort study

Objective To identify high risk clinical characteristics for subarachnoid haemorrhage in neurologically intact patients with headache. Design Multicentre prospective cohort study over five years. Setting Six university affiliated tertiary care teaching hospitals in Canada. Data collected from November 2000 until November 2005. Participants Neurologically intact adults with a non-traumatic headache peaking within an hour. Main outcome measures Subarachnoid haemorrhage, as defined by any of subarachnoid haemorrhage on computed tomography of the head, xanthochromia in the cerebrospinal fluid, or red blood cells in the final sample of cerebrospinal fluid with positive results on angiography. Physicians completed data collection forms before investigations. Results In the 1999 patients enrolled there were 130 cases of subarachnoid haemorrhage. Mean (range) age was 43.4 (16-93), 1207 (60.4%) were women, and 1546 (78.5%) reported that it was the worst headache of their life. Thirteen of the variables collected on history and three on examination were reliable and associated with subarachnoid haemorrhage. We used recursive partitioning with different combinations of these variables to create three clinical decisions rules. All had 100% (95% confidence interval 97.1% to 100.0%) sensitivity with specificities from 28.4% to 38.8%. Use of any one of these rules would have lowered rates of investigation (computed tomography, lumbar puncture, or both) from the current 82.9% to between 63.7% and 73.5%. Conclusion Clinical characteristics can be predictive for subarachnoid haemorrhage. Practical and sensitive clinical decision rules can be used in patients with a headache peaking within an hour. Further study of these proposed decision rules, including prospective validation, could allow clinicians to be more selective and accurate when investigating patients with headache.

Canadian C-Spine Rule study for alert and stable trauma patients: I. Background and rationale

This paper is Part I of a 2-part series to describe the background and methodology for the Canadian C-Spine Rule study to develop a clinical decision rule for rational imaging in alert and stable trauma patients. Current use of radiography is inefficient and variable, in part because there has been a lack of evidence-based guidelines to assist emergency physicians. Clinical decision rules are research-based decision-making tools that incorporate 3 or more variables from the history, physical examination or simple tests. The Canadian CT Head and C-Spine (CCC) Study is a large collaborative effort to develop clinical decision rules for the use of CT head in minor head injury and for the use of cervical spine radiography in alert and stable trauma victims. Part I details the background and rationale for the development of the Canadian C-Spine Rule. Part II will describe in detail the objectives and methods of the Canadian C-Spine Rule study.

The utility of a bone scan in the diagnosis of clinical scaphoid fracture

The incidence of true scaphoid fracture and the value of radionuclide scan was evaluated in a 1-year retrospective review of 54 emergency department patients with a preliminary diagnosis of clinical scaphoid fracture (snuff box tenderness and negative initial X-ray study). All emergency department charts of patients with a discharge diagnosis of clinical scaphoid fracture were reviewed to determine the number ultimately found to have a true scaphoid fracture and to ascertain how the diagnosis was actually achieved. All patients were managed by immobilization in a thumb spica cast for a period of 10-14 d, with repeat clinical assessment and radiographs at that time. The diagnosis of true scaphoid fracture was confirmed radiographically at the time of reassessment or, in the case of persistent tenderness and negative repeat radiographs, by the use of a technetium bone scan. In our study group, only 8 of 54 patients (14.8%) were found to have a final diagnosis of true scaphoid fracture. In 75% (6/8) of these patients, the diagnosis was made by technetium bone scans, as the radiographs remained negative at the time of reassessment. In addition, a bone scan revealed the presence of two previously unsuspected fractures (one distal radius fracture and one triquetral fracture) in two patients with continued clinical tenderness. This study confirms the previously reported low incidence of scaphoid fractures in patients with a diagnosis of clinical scaphoid fracture. It also demonstrates the importance of technetium bone scan as a diagnostic tool of increased sensitivity, as compared to traditional radiographs, in detecting the presence of scaphoid fractures and in detecting other clinically unsuspected fractures in this group of patients.

Differentiation between traumatic tap and aneurysmal subarachnoid hemorrhage: prospective cohort study

Objectives To describe the findings in cerebrospinal fluid from patients with acute headache that could distinguish subarachnoid hemorrhage from the effects of a traumatic lumbar puncture. Design A substudy of a prospective multicenter cohort study. Setting 12 Canadian academic emergency departments, from November 2000 to December 2009. Participants Alert patients aged over 15 with an acute non-traumatic headache who underwent lumbar puncture to rule out subarachnoid hemorrhage. Main outcome measure Aneurysmal subarachnoid hemorrhage requiring intervention or resulting in death. Results Of the 1739 patients enrolled, 641 (36.9%) had abnormal results on cerebrospinal fluid analysis with >1×106/L red blood cells in the final tube of cerebrospinal fluid and/or xanthochromia in one or more tubes. There were 15 (0.9%) patients with aneurysmal subarachnoid hemorrhage based on abnormal results of a lumbar puncture. The presence of fewer than 2000×106/L red blood cells in addition to no xanthochromia excluded the diagnosis of aneurysmal subarachnoid hemorrhage, with a sensitivity of 100% (95% confidence interval 74.7% to 100%) and specificity of 91.2% (88.6% to 93.3%). Conclusion No xanthochromia and red blood cell count <2000×106/L reasonably excludes the diagnosis of aneurysmal subarachnoid hemorrhage. Most patients with acute headache who meet this cut off will need no further investigations and aneurysmal subarachnoid hemorrhage can be excluded as a cause of their headache.

Factors influencing time to computed tomography in emergency department patients with suspected subarachnoid haemorrhage

Background CT has excellent sensitivity for subarachnoid haemorrhage (SAH) when performed within 6 hours of headache onset, but it is unknown to what extent patients with more severe disease are likely to undergo earlier CT, potentially inflating estimates of sensitivity. Our objective was to evaluate which patient and hospital factors were associated with earlier neuroimaging in alert, neurologically intact ED patients with suspected SAH. Methods We analysed data from two large sequential prospective cohorts of ED patients with acute headache undergoing CT for suspected SAH. We examined the time interval from headache onset to CT, both overall and subdivided from headache onset to hospital registration and from registration to CT. Results Among 2412 patients with headache, 194 had SAH, with 178 identified on unenhanced CT. Of these, 91 (51.1%) were identified by CT within 6 hours of headache onset and 87 after 6 hours. Patients with SAH had a shorter time from headache onset to hospital presentation (median 4.5 hours, IQR 1.7–22.7 vs 9.6 hours, IQR 2.8–46.0, p<0.001) and were imaged sooner after headache onset (6.4 hours, IQR 3.5–27.1 vs 12.6 hours, IQR 5.5–48.0, p<0.001) compared with those without SAH. The median time from in-hospital registration to CT scan was significantly shorter in those patients with SAH although this difference was less than 1 hour (1.9 hours, IQR 1.2–2.8 vs 2.5 hours, IQR 1.5–3.9, p<0.001). Arrival by ambulance (OR 3.1, 95% CI 1.94 to 4.98, p<0.001) and higher acuity at triage (OR 1.39, 95% CI 1.02 to 1.88, p=0.032) were among the factors associated with having CT imaging within 6 hours of headache onset. Conclusions Time from headache onset to imaging is moderately associated with positive imaging for SAH. Delay to hospital presentation accounts for the largest fraction of time to imaging, especially those without SAH. These findings suggest limited opportunity to reduce lumbar puncture rates simply by accelerating in-hospital processes when imaging delays are under 2 hours, as diagnostic yield of imaging decreases beyond the 6-hour imaging window from headache onset.