Traumatic injury to the posterior fossa: a secondary analysis and description of case series from the NEXUS head injury dataset.

Background: Traumatic brain injuries involving the posterior fossa are rare and case reports indicate they often result in severe outcomes. We seek to describe characteristics and outcomes of traumatic posterior fossa injuries. Methods: We performed a planned secondary analysis of all patients with posterior fossa injuries enrolled in the NEXUS head computed tomography (CT) validation study dataset. The dataset includes prospectively collected data on all patients undergoing non-contrast cranial CT following blunt traumatic head injury from April 2006 to December 2015, at four emergency departments comprising community and university sites, as well as urban, suburban and rural settings in California (Antelope Valley Hospital, San Francisco General Hospital, UCLA Ronald Reagan Medical Center, UCSF Fresno Community Regional Medical Center). We classified each patient into one of three injury patterns: Type I-notable traumatic injuries primarily above the tentorium, with minimal posterior fossa involvement; Type II-notable traumatic injuries both above and within the posterior fossa; and Type III-notable traumatic injuries primarily within the posterior fossa. We extracted demographic data for each patient as well as physician assessments of the NEXUS head CT and Canadian Head CT rule clinical criteria, mechanisms of injury, patient outcomes, and the location and types of intracranial injuries sustained. Findings: Of 11,770 patients in the database, 184 (1.6%) had posterior fossa injuries on CT imaging. Mean age was 55.4 years (standard deviation 22.5 years, range 2-96 years); 131 (71.2%) were males. We identified 63 patients with Type I injuries, 87 with Type II injuries, and 34 Type III injuries. The most common mechanisms of injury were falls (41%), pedestrian vs automobile (15%), and motor vehicle collisions (13%). On presentation most patients had altered mental status (72%), abnormal behavior (53%), or a neurologic deficit (55%). The majority of individuals, 151 (82%), had clinically important injuries and 111 (60%) required neurosurgical intervention. The dispositions for the subjects included 52 deaths (28%), 49 (27%) patients discharged home, and 48 (26%) discharged to rehabilitation facilities. When compared to individuals with Type I and Type II injuries, patients with Type III injuries had lower mortality (6% vs 30% and 35%) and higher percentage of patients discharged home (60% vs 19% and 21%). Interpretation: Patients with Type I and II injury patterns (those that involve both the posterior fossa and supratentorium) experienced high mortality and disability. Patients with Type III injuries (isolated posterior fossa) had a better prognosis. Funding: None.

Characteristics of Intracranial Injuries in Pediatric Patients Following Blunt Head Trauma.

OBJECTIVES: Pediatric head trauma is a frequent reason for presentation to the emergency department. Despite this, there are few reports on specific characteristics and injury patterns in head injured children. The goal of this study was to evaluate head injury patterns in children with blunt head injury and their prevalence by age group. METHODS: This is a planned secondary analysis of the NEXUS II Head CT validation study. Consecutive patients with blunt head trauma were enrolled between 2006 and 2015. Demographics and criteria from 2 clinical decision instruments (NEXUS and Canadian Head CT rules) were gathered at the time of enrollment. We abstracted and cataloged injuries for pediatric patients based on radiologist report. Frequencies of injuries and severity were analyzed by developmental age group. RESULTS: A total of 1018 pediatric patients were enrolled, 128 (12.6%) of whom had an injury on computed tomography scan. Median age was 11.9 (Interquartile range 4.5-15.5) for all patients and 12 (4.8-15.5) for injured patients. Of injured patients, 49 (38.3%) had a significant injury, and 27 (21.1%) received an intervention. Teenagers had the highest rate of significant injury (50%) and intervention (30%). Injuries were most frequently noted in the temporal (46.1%), frontal (45.3%), and parietal (45.3%) regions. Subarachnoid hemorrhage (29.7%) and subdural hematoma (28.9%) were the most common injuries observed.Intraparenchymal hemorrhage and cerebral edema were more prevalent in older age groups. The most common injury mechanism overall was fall from height (24.7%). Motor vehicle accidents and nonmotorized wheeled vehicle accidents were more common in older patients. CONCLUSIONS: Serious injuries requiring intervention were rarely encountered in pediatric patients experiencing blunt head trauma. Mechanisms of injury, type of injury, and rates of intervention varied between developmental age groups.

Blunt Head Injury in the Elderly: Analysis of the NEXUS II Injury Cohort.

BACKGROUND: Changes with aging make older patients vulnerable to blunt head trauma and alter the potential for injury and the injury patterns seen among this expanding cohort. High-quality care requires a clear understanding of the factors associated with blunt head injuries in the elderly. Our objective was to develop a detailed assessment of the injury mechanisms, presentations, injury patterns, and outcomes among older blunt head trauma patients. METHODS: We conducted a planned secondary analysis of patients aged 65 or greater who were enrolled in the National Emergency X-Radiography Utilization Study (NEXUS) Head Computed Tomography validation study. We performed a detailed assessment of the demographics, mechanisms, presentations, injuries, interventions, and outcomes among older patients. RESULTS: We identified 3,659 patients aged 65 years or greater, among the 11,770 patients enrolled in the NEXUS validation study. Of these older patients, 325 (8.9%) sustained significant injuries, as compared with significant injuries in 442 (5.4%) of the 8,111 younger patients. Older females (1,900; 51.9%) outnumbered older males (1,753; 47.9%), and occult presentations (exhibiting no high-risk clinical criteria beyond age) occurred in 48 (14.8%; 95% confidence interval (CI) 11.1 to 19.1) patients with significant injuries. Subdural hematomas (377 discreet lesions in 299 patients) and subarachnoid hemorrhages (333 discreet instances in 256 patients) were the most frequent types of injuries occurring in our elderly population. A ground-level fall was the most frequent mechanism of injury among all patients (2,211; 69.6%), those sustaining significant injuries (180; 55.7%), and those who died of their injuries (37; 46.3%), but mortality rates were highest among patients experiencing a fall from a ladder (11.8%; 4 deaths among 34 cases [95% CI 3.3% to 27.5%]) and automobile versus pedestrian events (10.7%; 16 deaths among 149 cases [95% CI 6.3% to 16.9%]). Among older patients who required neurosurgical intervention for their injuries, only 16.4% (95% CI 11.1% to 22.9%) were able to return home, 32.1% (95% CI 25.1% to 39.8%) required extended facility care, and 41.8% (95% CI 34.2% to 49.7%) died from their injuries. CONCLUSIONS: Older blunt head injury patients are at high risk of sustaining serious intracranial injuries even with low-risk mechanisms of injury, such as ground-level falls. Clinical evaluation is unreliable and frequently fails to identify patients with significant injuries. Outcomes, particularly after intervention, can be poor, with high rates of long-term disability and mortality.

Accuracy of physician gestalt in prediction of significant abdominal and pelvic injury in adult blunt trauma patients.

OBJECTIVE: Focusing on potential missed injury rates and sensitivity of low-risk of injury predictions, we sought to evaluate the accuracy of physician gestalt in predicting clinically significant injury (CSI) in the abdomen and pelvis among blunt trauma patients presenting to the emergency department (ED). METHODS: We collected gestalt data on physicians caring for adult blunt trauma patients who received abdominal/pelvic computed tomography (CT) at three Level I and one Level II trauma centers. The primary outcome of CSI was defined as injury on abdominal/pelvic CT requiring hospitalization or intervention. Physicians evaluating trauma patients estimated the likelihood of CSI prior to abdominal/pelvic CT review (response choices: <2%, 2%-10%, 11%-20%, 21%-40%, >40%). We evaluated potential missed injury rates (prevalence of CSI) and sensitivity for prediction categories, as well as calibration and area under the receiver operating characteristic (AUROC) curve for overall physician gestalt. RESULTS: Of 2030 patients, 402 (20%) had an injury on abdominal/pelvic CT and 270 (13%) had CSI. The <2% risk of CSI gestalt cutoff had a potential missed injury rate of 5.6% and a sensitivity of 95.2% (95% confidence interval [CI] 91.7%-97.3%). The 0%-10% cutoff of CSI gestalt had a potential missed injury rate of 6.3% (95% CI, 5.0%-7.9%) and a sensitivity of 75.2% (95% CI 69.5%-80.1%). With an overall AUROC of 0.699 (95% CI 0.679-0.719), physician gestalt was moderately accurate and calibrated for the midranges of predicted risk but poorly calibrated at the extremes. CONCLUSIONS: Physician gestalt for the prediction of adult abdominal and pelvic CSI is moderately accurate and calibrated. However, the potential missed CSI rate and low sensitivity of the low perceived risk of injury cutoffs indicate that gestalt by itself is insufficient to direct selective abdominal/pelvic CT use in adult blunt trauma patient evaluation.

Physical Examination Sensitivity for Skull Fracture in Pediatric Patients With Blunt Head Trauma: A Secondary Analysis of the National Emergency X-Radiography Utilization Study II Head Computed Tomography Validation Study.

STUDY OBJECTIVE: We evaluated the emergency department (ED) providers' ability to detect skull fractures in pediatric patients presenting with blunt head trauma. METHODS: This was a secondary analysis of the National Emergency X-Radiography Utilization Study (NEXUS) Head computed tomography (CT) validation study. Demographics and clinical characteristics were analyzed for pediatric patients. Radiologist interpretations of head CT imaging were abstracted and cataloged. Detection of skull fractures was evaluated through provider response to specific clinical decision instrument criteria (NEXUS or Canadian head CT rules) at the time of initial patient evaluation. The presence of skull fracture was determined by formal radiologist interpretation of CT imaging. RESULTS: Between April 2006, and December 2015, 1,018 pediatric patients were enrolled. One hundred twenty-eight (12.5%) children had a notable injury reported on CT head. Skull fracture was present in most (66.4%) children with intracranial injuries. The sensitivity and specificity of provider physical examination to detect skull fractures was 18.5% (95% confidence interval 10.5% to 28.7%) and 96.6% (95.3% to 97.7%), respectively. The most common injuries associated with skull fractures were subarachnoid hemorrhage (27%) and subdural hematoma (22.3%). CONCLUSION: Skull fracture is common in children with intracranial injury after blunt head trauma. Despite this, providers were found to have poor sensitivity for skull fractures in this population, and these injuries may be missed on initial emergency department assessment.

Developing a decision instrument to guide abdominal-pelvic imaging of blunt trauma patients: Methodology and protocol of the NEXUS abdominal-pelvic imaging study.

Although computed tomography (CT) of the abdomen and pelvis (A/P) can provide crucial information for managing blunt trauma patients, liberal and indiscriminant imaging is expensive, can delay critical interventions, and unnecessarily exposes patients to ionizing radiation. Currently no definitive recommendations exist detailing which adult blunt trauma patients should receive A/P CT imaging and which patients may safely forego CT. Considerable benefit could be realized by identifying clinical criteria that reliably classify the risk of abdominal and pelvic injuries in blunt trauma patients. Patients identified as "very low risk" by such criteria would be free of significant injury, receive no benefit from imaging and therefore could be safely spared the expense and radiation exposure associated with A/P CT. The goal of this two-phase nationwide multicenter observational study is to derive and validate the use of clinical criteria to stratify the risk of injuries to the abdomen and pelvis among adult blunt trauma patients. We estimate that nation-wide implementation of a rigorously developed decision instrument could safely reduce CT imaging of adult blunt trauma patients by more than 20%, and reduce annual radiographic charges by $180 million, while simultaneously expediting trauma care and decreasing radiation exposure with its attendant risk of radiation-induced malignancy. Prior to enrollment we convened an expert panel of trauma surgeons, radiologists and emergency medicine physicians to develop a consensus definition for clinically significant abdominal and pelvic injury. In the first derivation phase of the study, we will document the presence or absence of preselected candidate criteria, as well as the presence or absence of significant abdominal or pelvic injuries in a cohort of blunt trauma victims. Using recursive partitioning, we will examine combinations of these criteria to identify an optimal "very low risk" subset that identifies injuries with a sensitivity exceeding 98%, excludes injury with a negative predictive value (NPV) greater than 98%, and retains the highest possible specificity and potential to decrease imaging. In Phase 2 of the study we will validate the performance of a decision rule based on these criteria among a new cohort of patients to ensure that the criteria retain high sensitivity, NPV and optimal specificity. Validating the sensitivity of the decision instrument with high statistical precision requires evaluations on 317 blunt trauma patients who have significant abdominal-pelvic injuries, which will in turn require evaluations on approximately 6,340 blunt trauma patients. We will estimate potential reductions in CT imaging by counting the number of abdominal-pelvic CT scans performed on "very low risk" patients. Reductions in charges and radiation exposure will be determined by respectively summing radiographic charges and lifetime decreases in radiation morbidity and mortality for all "very low risk" cases. Trial registration: Clinicaltrials.gov trial registration number: NCT04937868.

Prevalence of Intracranial Injury in Adult Patients With Blunt Head Trauma With and Without Anticoagulant or Antiplatelet Use.

STUDY OBJECTIVE: We determine the prevalence of significant intracranial injury among adults with blunt head trauma who are receiving preinjury anticoagulant or antiplatelet medications. METHODS: This was a multicenter, prospective, observational study conducted from December 2007 to December 2015. Patients were enrolled in 3 emergency departments (EDs) in the United States. Adults with blunt head trauma who underwent neuroimaging in the ED were included. Use of preinjury aspirin, clopidogrel, and warfarin was recorded. Data on direct oral anticoagulants were not specifically recorded. The primary outcome was prevalence of significant intracranial injury on neuroimaging. The secondary outcome was receipt of neurosurgical intervention. RESULTS: Among 9,070 patients enrolled in this study, the median age was 53.8 years (interquartile range 34.7 to 74.3 years) and 60.7% were men. A total of 1,323 patients (14.6%) were receiving antiplatelet medications or warfarin, including 635 receiving aspirin alone, 109 clopidogrel alone, and 406 warfarin alone. Compared with that of patients without any coagulopathy, the relative risk of significant intracranial injury was 1.29 (95% confidence interval [CI] 0.88 to 1.87) for patients receiving aspirin alone, 0.75 (95% CI 0.24 to 2.30) for those receiving clopidogrel alone, and 1.88 (95% CI 1.28 to 2.75) for those receiving warfarin alone. The relative risk of significant intracranial injury was 2.88 (95% CI 1.53 to 5.42) for patients receiving aspirin and clopidogrel in combination. CONCLUSION: Patients receiving preinjury warfarin or a combination of aspirin and clopidogrel were at increased risk for significant intracranial injury, but not those receiving aspirin alone. Clinicians should have a low threshold for neuroimaging when evaluating patients receiving warfarin or a combination of aspirin and clopidogrel.

Identification of Clinical Characteristics Associated With High-Level Care Among Patients With Skin and Soft Tissue Infections.

STUDY OBJECTIVE: Serious adverse outcomes associated with skin and soft tissue infections are uncommon, and current hospitalization rates appear excessive. It would be advantageous to be able to differentiate between patients who require high-level inpatient services and those who receive little benefit from hospitalization. We sought to identify characteristics associated with the need for high-level inpatient care among emergency department patients presenting with skin and soft tissue infections. METHODS: We conducted a nonconcurrent review of existing records to identify emergency department (ED) patients treated for skin and soft tissue infections. For each case, we recorded the presence or absence of select criteria and whether the patient needed high-level care, defined as ICU admission, operating room surgical intervention, or death as the primary outcome. We applied recursive partitioning to identify the principal criteria associated with high-level care. RESULTS: We identified 2,923 patients, including 84 experiencing high-level events. Recursive partitioning identified 6 variables associated with high-level outcomes: abnormal computed tomography, magnetic resonance imaging, or ultrasonographic imaging result; systemic inflammatory response syndrome; history of diabetes; previous infection at the same location; older than 65 years; and an infection involving the hand. One or more of these variables were present in all 84 patients requiring high-level care. CONCLUSION: A limited number of simple clinical characteristics appear to be able to identify skin and soft tissue infection patients who require high-level inpatient services. Further research is needed to determine whether patients who do not exhibit these criteria can be safely discharged from the ED.

Validation of the Pediatric NEXUS II Head Computed Tomography Decision Instrument for Selective Imaging of Pediatric Patients with Blunt Head Trauma.

BACKGROUND: Data suggest that clinicians, when evaluating pediatric patients with blunt head trauma, may be overordering head computed tomography (CT). Prior decision instruments (DIs) aimed at aiding clinicians in safely forgoing CTs may be paradoxically increasing CT utilization. This study evaluated a novel DI that aims for high sensitivity while also improving specificity over prior instruments. METHODS: We conducted a planned secondary analysis of the NEXUS Head CT DI among patients less than 18 years old. The rule required patients satisfy seven criteria to achieve "low-risk" classification. Patients were assigned "high-risk" status if they fail to meet one or more criteria. Our primary outcome was the ability of the rule to identify all patients requiring neurosurgical intervention. RESULTS: The study enrolled 1,018 blunt head injury pediatric patients. The DI assigned high-risk status to 27 of 27 patients requiring neurosurgical intervention (sensitivity = 100.0%, 95% confidence interval [CI] = 87.2%-100%]). The instrument assigned low-risk status to 330 of 991 patients who did not require neurosurgical intervention (specificity = 33.3%, 95% CI = 30.3%-36.3%). None of the 991 low-risk patients required neurosurgical intervention (negative predictive value [NPV] = 100%, 95% CI = 99.6%-100%). The DI correctly assigned high-risk status to 48 of the 49 patients with significant intracranial injuries, yielding a sensitivity of 98.0% (95% CI = 89.1%-99.9%). The instrument assigned low-risk status to 329 of 969 patients who did not have significant injuries to yield a specificity of 34.0% (95% CI = 31.0%-37.0%). Significant injuries were absent in 329 of the 330 patients assigned low-risk status to yield a NPV of 99.7% (95% CI = 98.3%-100%). CONCLUSIONS: The Pediatric NEXUS Head CT DI reliably identifies blunt trauma patients who require head CT imaging and could significantly reduce the use of CT imaging.

Validation of the sensitivity of the National Emergency X-Radiography Utilization Study (NEXUS) Head computed tomographic (CT) decision instrument for selective imaging of blunt head injury patients: An observational study.

BACKGROUND: Clinicians, afraid of missing intracranial injuries, liberally obtain computed tomographic (CT) head imaging in blunt trauma patients. Prior work suggests that clinical criteria (National Emergency X-Radiography Utilization Study [NEXUS] Head CT decision instrument [DI]) can reliably identify patients with important injuries, while excluding injury, and the need for imaging in many patients. Validating this DI requires confirmation of the hypothesis that the lower 95% confidence limit for its sensitivity in detecting serious injury exceeds 99.0%. A secondary goal of the study was to complete an independent validation and comparison of the Canadian and NEXUS Head CT rules among the subgroup of patients meeting the inclusion and exclusion criteria. METHODS AND FINDINGS: We conducted a prospective observational study of the NEXUS Head CT DI in 4 hospital emergency departments between April 2006 and December 2015. Implementation of the rule requires that patients satisfy 8 criteria to achieve "low-risk" classification. Patients are excluded from "low-risk" classification and assigned "high-risk" status if they fail to meet 1 or more criteria. We examined the instrument's performance in assigning "high-risk" status to patients requiring neurosurgical intervention among a cohort of 11,770 blunt head injury patients. The NEXUS Head CT DI assigned high-risk status to 420 of 420 patients requiring neurosurgical intervention (sensitivity, 100.0% [95% confidence interval [CI]: 99.1%-100.0%]). The instrument assigned low-risk status to 2,823 of 11,350 patients who did not require neurosurgical intervention (specificity, 24.9% [95% CI: 24.1%-25.7%]). None of the 2,823 low-risk patients required neurosurgical intervention (negative predictive value [NPV], 100.0% [95% CI: 99.9%-100.0%]). The DI assigned high-risk status to 759 of 767 patients with significant intracranial injuries (sensitivity, 99.0% [95% CI: 98.0%-99.6%]). The instrument assigned low-risk status to 2,815 of 11,003 patients who did not have significant injuries (specificity, 25.6% [95% CI: 24.8%-26.4%]). Significant injuries were absent in 2,815 of the 2,823 patients assigned low-risk status (NPV, 99.7% [95% CI: 99.4%-99.9%]). Of our patients, 7,759 (65.9%) met the inclusion and exclusion criteria of the Canadian Head CT rule, including 111 patients (1.43%) who required neurosurgical intervention and 306 (3.94%) who had significant intracranial injuries. In our study, the Canadian criteria for neurosurgical intervention identified 108 of 111 patients requiring neurosurgical intervention to yield a sensitivity of 97.3% (95% CI: 92.3%-99.4%) and exhibited a specificity of 58.8% (95% CI: 57.7%-59.9%). The NEXUS rule, when applied to this same cohort, identified all 111 patients requiring neurosurgical intervention, yielding a sensitivity of 100% (95% CI: 96.7%-100.0%) with a specificity of 32.6% (95% CI: 31.5%-33.6%). Our study found that the Canadian medium-risk factors identified 301 of 306 patients with significant injuries (sensitivity = 98.4%; 95% CI: 96.2%-99.5%), while the NEXUS rule identified 299 of these patients (sensitivity = 97.7%; 95% CI: 95.3%-99.1%). In our study, the Canadian medium-risk rule exhibited a specificity of 12.3% (95% CI: 11.6%-13.1%), while the NEXUS rule exhibited a specificity of 33.3% (95% CI: 32.3%-34.4%). Limitations of the study may arise from application of the rule by different clinicians in different environments. Clinicians may vary in their interpretation and application of the instrument's criteria and risk assignment and may also vary in deciding which patients require intervention. The instrument's specificity is also subject to spectrum bias and may change with variations in the proportion of "low-risk" patients seen in other centers. CONCLUSIONS: The NEXUS Head CT DI reliably identifies blunt trauma patients who require head CT imaging and could significantly reduce the use of CT imaging.

Injury Severity Score Inflation Resulting From Pan-Computed Tomography in Patients With Blunt Trauma.

STUDY OBJECTIVE: All articles that demonstrate a mortality benefit from liberal pan-computed tomography (CT) use in patients with blunt trauma have relied on Injury Severity Score (ISS) to control for morbidity. This mortality benefit may be artifact, the result of an increased use of a sensitive diagnostic modality rather than a true benefit. We quantify the magnitude of ISS inflation in patients with blunt trauma who are undergoing routine pan-CT compared with patients who receive more selective scanning. METHODS: This study re-analyzes data collected from a previous study of pan-CT use in patients with blunt trauma in which surveyed emergency physicians prospectively indicated which portion of a pan-CT they wished to obtain. The trauma surgeons who jointly managed all patients in this study ultimately decided which CTs to obtain. We recalculated the ISS excluding injuries found on the undesired CT scans that did not lead to a predefined set of critical actions and compared original and recalculated ISS. RESULTS: There were 701 study subjects who received a total of 2,615 scans. Of these, there were 992 undesired scans. Ninety-nine of the obtained undesired scans, performed in 92 patients, had noncritical abnormalities. The original ISS for these 92 patients was 10 (IQR 5, 18); the recalculated ISS was 5 (interquartile range 1, 10), a 50% decrease. CONCLUSION: Although the median ISS for our study was lower than that of previous studies claiming a mortality benefit, ISS inflation appears to be a real phenomenon and may confound studies that use ISS to control for morbidity.

Symptomatic Pneumorrhachis After an Epidural Blood Patch.

BACKGROUND: Pneumorrhachis (PR), the presence of air within the spinal canal, is a rare, radiologic epiphenomenon arising from traumatic, nontraumatic, and iatrogenic causes. Often asymptomatic, PR is usually managed conservatively. However, PR can be associated with underlying serious pathology and can become symptomatic, requiring more aggressive diagnostic and treatment modalities from the treating physician. Although well known in the anesthesia literature, this case report is the first in the emergency medicine literature to describe iatrogenic, symptomatic PR presenting in the emergency department (ED). CASE REPORT: A 34-year-old woman presented to the ED with a postural puncture headache after epidural anesthesia for a vaginal delivery. An epidural blood patch was administered, after which the patient acutely developed cervical radicular pain. Computed tomography angiography of the head and neck revealed epidural PR. Conservative treatment with analgesia, intravenous fluids, and bed rest was administered. Her pain improved significantly, and at 5-month follow-up, she remained symptom-free. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: PR is a rare and usually benign disease, especially in the setting of an iatrogenic cause such as lumbar puncture. However, in traumatic settings, PR in the intradural space should alert the emergency physician to search for underlying serious pathology if it has not already been found. Finally, PR can become symptomatic, and treatment will depend on the severity of symptoms.

Selective use of computed tomography compared with routine whole body imaging in patients with blunt trauma.

STUDY OBJECTIVE: Routine pan-computed tomography (CT, including of the head, neck, chest, abdomen/pelvis) has been advocated for evaluation of patients with blunt trauma based on the belief that early detection of clinically occult injuries will improve outcomes. We sought to determine whether selective imaging could decrease scan use without missing clinically important injuries. METHODS: This was a prospective observational study of 701 patients with blunt trauma at an academic trauma center. Before scanning, the most senior emergency physician and trauma surgeon independently indicated which components of pan-CT were necessary. We calculated the proportion of scans deemed unnecessary that: (a) were abnormal and resulted in a pre-defined critical action or (b) were abnormal. RESULTS: Pan-CT was performed in 600 of the patients; the remaining 101 underwent limited scanning. One or both physicians indicated a willingness to omit 35% of the individual scans. An abnormality was present in 18% of scans, including 22% of desired scans and 10% of undesired scans. Among the 95 patients who had one of the 102 undesired scans with abnormal results, 3 underwent a predefined critical action. There is disagreement among the authors about the clinical significance of the abnormalities found on the 99 undesired scans that did not lead to a critical action. CONCLUSION: Selective scanning could reduce the number of scans, missing some injuries but few critical ones. The clinical importance of injuries missed on undesired scans was subject to individual interpretation, which varied substantially among authors. This difference of opinion serves as a microcosm of the larger debate on appropriate use of expensive medical technologies.