2005 CAEP / ACMU Scientific Abstracts - Oral Presentations: 30-44

Trends in the incidence of spinal cord injury in Alberta.

Dryden DM, Saunders LD, Rowe BH, May LA, Yiannakoulias N, Svenson LW, Schopflocher DP, Voaklander DC. BC Rural and Remote Health Research Institute, University of Northern British Columbia, Prince George, BC

INTRODUCTION: The impact of traumatic spinal cord injury (SCI) can be devastating, especially when accompanied by permanent loss of sensory or motor function. The annual incidence rate of SCI in Alberta is estimated at 44.3 per million population (95% CI: 39.8, 48.7). The highest incidence occurs among males, adolescents and young adults. The leading causes of SCI are motor vehicle collisions and falls. The objective of this study was to examine the trends in incidence of SCI in Alberta over eight years. METHODS: This population-based study used administrative data from centralized health care databases. Inclusion criteria were persons with SCI (ICD-9-CM diagnostic codes 806.x or 952.x) who were admitted to a trauma centre in Alberta between April 1992/93 and March 1999/00. Measures of incidence included the number of SCI cases and age-sex standardized incidence rates. The 2001 population of Alberta was used as the standard. RESULTS: Over the 8-year study period, 917 individuals sustained a SCI. The mean number of cases per year was 115 and ranged from 104 injuries in 1999/00 to 122 in 1997/98 and 1998/99. The annual age-standardized rates ranged from 35.2 injuries (95% CI: 28.5, 41.9) per million population in 1999/00 to 45.6 (95% CI: 37.3, 53.9) in 1992/93. The annual rates varied over the study period; however, there was no significant linear trend (p = 0.15). For all years, the incidence rate for males was higher than for females.CONCLUSIONS: SCI incidence trends in Alberta suggest that SCI is not decreasing. Since there is currently no cure for SCI, primary prevention efforts are critical. Targeted injury control initiatives must be implemented if the injury statistics are to improve. Key words: spinal cord injury; trauma; injury surveillance

Clinical predictors for pelvic fracture following severe trauma.

Perry JJ, Forbes M, Stiell IG, Mortensen M, Symington C. Department of Emergency Medicine, University of Ottawa, Ottawa, ON

INTRODUCTION: Pelvic x-ray is recommended by the Advanced Trauma Life Support course for blunt trauma. This study determined the correlation of clinical findings to pelvic fracture and the feasibility of developing a clinical decision rule. METHODS: This historical cohort study was conducted at a university level 1 trauma center. We enrolled all adult blunt trauma patients with an injury severity score of >12 for one year. Patients transfers with confirmed pelvic fracture or >48 hrs from injury were excluded. Data was extracted from patient's trauma record and electronic diagnostic imaging (DI) record. Patients without pelvic DI had discharge summary and subsequent DI checked for missed fractures. We defined pelvic fracture as any fracture or displacement to the pelvic ring. Descriptive, univariate and logistic regression analysis were performed. RESULTS: Of 342 patients identified, 254 were eligible. Injury mechanism included: fall 38.8%, motor vehicle accident 39.2%, pedestrian 4.7%, recreational vehicle 5.1%, and other 12.2%. Enrolled patients had the following characteristics: pelvic fracture 6.3%; mean age 47.3 yrs; median GCS 15 (IQR 11, 15); tender with palpation of pelvis 20.5%; bruise at pelvis 6.7%; pelvic instability 2.4%; decreased rectal tone 3.6%; gross blood in urine 23.4%; pelvic x-ray 30.2%; pelvic CT 31.9%; CT and/or x-ray 42.9%. Table 1 (of Abstract 31) shows % injury and non-injury with findings, p-value, adjusted odds ratio:

CONCLUSION: Pelvic fracture is relatively rare. Tenderness on palpation of the pelvis, pelvic instability and decreased rectal tone correlate highly with pelvic fracture. Deriving a clinical decision rule is likely feasible and future research should address this issue. Key words: ATLS; pelvic fracture

Survey of domestic violence screening protocols in Canadian emergency departments.

McClennan SK, Worster A, MacMillan H. Division of Emergency Medicine, McMaster University, Hamilton, ON

INTRODUCTION: At least 6% of the adult female population are victims of domestic violence. Approximately 30% of Canadian emergency departments (EDs) routinely screen for these women. In 2003, the Canadian Task Force on Preventive Health Care (CTFPHC) reported no evidence in favour for or against this practice. The objectives of this study were to determine: the proportion of Canadian EDs with a universal screening program for victims of domestic violence; the proportion with domestic violence intervention policies and procedures; changes in practices in the past ten years and; changes in ED domestic violence policies and procedures since the CTFPHC Recommendations. METHODS: A cross-sectional survey of a stratified random sample of all 638 full-service, Canadian EDs was conducted between September and December 2004 using the Dillman method. Participants were asked about their ED policies and procedures for the identification and management of victims of domestic violence. Validation of responses was via receipt and review of the institution's written policies and procedures.RESULTS: The response rate for the 114 participating sites was 78.9% (95% CI: 70.6, 85.4) with 12.3% (95% CI: 7.5, 20.0) reporting a universal screening program and 27.2% (95% CI: 19.9, 36.0) reporting intervention policies and procedures. Ten years ago, 13% (95% CI: 9.1, 18.6) of Canadian EDs reported use of a universal screening program and 39.4% (95% CI: 32.8, 46.3) reported having policies and procedures for victims of domestic violence. All 7.0% (95% CI: 3.6, 13.2) of respondents that made changes to their policies and procedures since the CTFPHC 2003 Recommendations were contrary to the recommendations.CONCLUSIONS: Despite a CTFPHC recommendation concluding insufficient evidence to recommend for or against screening for violence against women, there has been no significant change in how EDs screen for victims of domestic violence in the past ten years. Future work needs to focus on knowledge dissemination of this evidence-based information. Key words: domestic violence

Emergency department triage: evaluating a computerized triage tool and its implementation strategies.

Dong SL, Bullard MJ, Meurer DP, Blitz S, Rowe BH. Department of Emergency Medicine, University of Alberta, Edmonton, AB

INTRODUCTION: Emergency Department (ED) triage prioritizes patients based on urgency of care. The Canadian Triage and Acuity Scale (CTAS) is the nationally recognized standard. A web-based triage tool (eTRIAGE) based on CTAS has been developed. We describe its implementation into a busy ED and compare it triage without electronic decision support. METHODS: This prospective study took place in a tertiary care ED in a large urban centre. In Phase 1, duty triage nurses did not use any electronic decision support. In Phase 2, the ED deployed eTRIAGE after providing a three hour training course to a small cohort of triage nurses who were to share this knowledge with their untrained colleagues during regular triage shifts. In Phase 3, a group of eight triage nurses, selected for their triage experience and interest, underwent further training with eTRIAGE. In each phase, patients were assessed first by the triage nurse, using memory in Phase 1 and eTRIAGE in Phases 2 and 3. A blinded study nurse then independently used eTRIAGE to triage each patient. Inter-rater agreement is reported using kappa (weighted κ) statistics. RESULTS: Phase 1 enrolled 722 patients with 693 (96.0%) complete records, Phase 2 enrolled 570 patients with 541 (94.9%) complete records, and Phase 3 enrolled 577 patients with 569 (98.6%) complete records; phases ranged from 5-9 weeks to complete. At least 37 different triage nurses made the initial triage assessments in Phases 1 and 2. Inter-rater agreement during Phase 1 was fair (weighted κ = 0.36, 95% CI 0.31, 0.42) but improved to moderate in Phase 2 (weighted κ = 0.41, 95% CI 0.35, 0.47) and Phase 3 (weighted κ = 0.52, 95% CI 0.46, 0.57). CONCLUSIONS: Agreement between study nurses using eTRIAGE and duty triage nurses improved when duty nurses were provided eTRIAGE over memory. Further improvement was observed employing nurses selected for triage interest and provided with further eTRIAGE training. Continued attempts to improve the triage process, the triage environment, and training appear warranted. Key words: CTAS; triage

Should spectrophotometry be used to diagnose xanthochromia in the cerebrospinal fluid of alert patients suspected of having subarachnoid hemorrhage?

Perry JJ, Sivilotti M, Stiell IG, Wells GA, Raymond JJ, Mortensen M, Symington C. Department of Emergency Medicine, University of Ottawa, Ottawa, ON

INTRODUCTION: Clinicians rely on the absence of xanthochromia in the cerebrospinal fluid (CSF) obtained by lumbar puncture (LP) several hours after headache to exclude subarachnoid hemorrhage (SAH). Several authorities and guidelines from the United Kingdom (UKNEQAS) advocate spectrophotometry to measure xanthochromia, but most hospitals in North America rely on visual inspection. This study examines the accuracy and impact of spectrophotometry for SAH. METHODS: This prospective cohort study was conducted at three university tertiary care EDs. We enrolled neurologically intact patients >15 yrs with non-traumatic acute (<1 hour from onset to peak) headache who had a LP to rule out SAH. CSF was centrifuged immediately, then frozen and analyzed later in batch (Milton Roy Spectronic). Four definitions of spectrophotmetric xanthochromia were compared to visual inspection. 6-month telephone follow-up was conducted.RESULTS: We enrolled 220 patients (mean age 42 ± 16 yrs; CT rate 87.7%; angiography rate 5.9%). Two SAH were identified with current practice: 1 with aneurysm on CT and 1 with blood in CSF with positive angiography. No additional SAH were identified on follow-up. Table 1 (of Abstract 34) reports sensitivity, specificity and percentage requiring an angiogram (change from current practice) for each definition:

CONCLUSION: Spectrophotometric xanthochromia has a low specificity for SAH. Each spectophotometric definition would result in a substantial increase in angiography, and would therefore be expected to identify more incidental aneurysms, increase patient anxiety and expose patients to unnecessary surgical or investigational complications without benefit. Key words: subarachnoid hemorrhage; lumbar puncture

Why do some use the emergency department more than others?

McMaster R, Kozyrskyj AL. Department of Community Health Sciences, University of Manitoba, Winnipeg, MB

INTRODUCTION: The objective of this study was to describe high users of emergency departments (ED) in terms of their patient characteristics, comorbidities and health care use, through comparison to low users.METHODS: Based on visit counts over one year, a cohort of Winnipeg ED users were classified as high (four or more visits a year) or low users. Anonymized linkage to population-based health care databases in Manitoba allowed for a more comprehensive description of the cohort. Study variables included gender, age, income, use of health care services, and multiple morbidity (using an established case-mix classification system).RESULTS: In 2001, 120456 users made 197707 visits to the six adult emergency departments in Winnipeg. Of these, 8007 (6.63%) were classified as high users, contributing to 24.3% of the total visits. High users, on average, were older (51.3 vs. 42.7 years), more often female (52.5% vs. 50.7%), had more physician visits (18.9 vs. 9.7) and hospitalizations (2.24 vs. 1.45) during the study year, when compared to low users. 48.7% of the high users had at least seven different morbidities; in the low user group, this percentage dropped to 18.9%. Further refinement of ED user morbidity was carried out using an extended diagnosis clustering (EDC) methodology. The most prevalent EDC among high users was depression, anxiety and neurosis (33.05%). Substance use and congestive heart failure were also more prevalent in high users (4.52 and 3.17 times more often, respectively). High users identified as having depression, anxiety and neurosis were less likely to have other major morbidities (14.9%), while those high users with congestive heart failure showed a higher prevalence of other major morbidities (37.6%). CONCLUSIONS: High users of emergency departments in Winnipeg use a disproportionate amount of emergency department services and are a complex group of patients with multiple morbidities and variable health care needs.Key words: emergency health services; utilization

Predictive validity of the triage risk screening tool in a Canadian emergency department.

Fan J, Worster A, Fernandes CMB, Lever J, Roberts R. Division of Emergency Medicine, McMaster University, Hamilton, ON

INTRODUCTION: The Triage Risk Screening Tool (TRST) developed in Ohio has never been validated externally. This study's purpose was to evaluate the predictive validity of TRST for emergency department (ED) re-visits, hospital admissions, and long-term care (LTC) facility placement in a Canadian setting. Methods: From March 1 to 24, 2004, a prospective observational cohort study of a convenience sample of patients ≥65 years old discharged from a tertiary care academic ED were given a TRST score without physician knowledge. Patients were excluded if they were LTC facility residents, previously enrolled, or had no proxy if cognitively impaired. The primary outcome was any ED re-visit, hospital admission, or LTC facility placement event at one, four, and six-months. Binary logistic regression was used to model the primary outcome odds using the TRST score as an indicator variable. Demographic variables with significant univariate analyses were added to the model. Odds ratios with confidence intervals for each variable were calculated. Somers' D rank correlation test measured the association between observed responses and predicted odds.RESULTS: 218 patients were screened, 193 patients consented to follow-up, 73 met exclusion criteria. 120 patients were enrolled, with one patient lost to follow-up. Age was associated with the primary outcome in univariate analyses (p = 0.001). Logistic regression showed that with each TRST score increase by one, the primary outcome odds increased by 1.60 (95% CI: 1.02, 2.50), 1.39 (95% CI: 0.97, 2.00), and 1.44 (95% CI: 1.00, 2.06) times at one, four, and six-months. Despite a good-fit (p = 0.274), this model correctly predicted only 61.0% to 62.9% of observed primary outcomes (Somers' D value: 0.27 to 0.29).CONCLUSIONS: Although the TRST works reasonably well to risk stratify Canadian elders for the occurrence of any ED re-visit, hospital admission, or LTC placement over six-months, it does not allow good patient-level predictions for these outcomes.Key words: emergency health services; utilization

Reporting of notifiable diseases in the ED: a survey of emergency physician knowledge, practices, and perceived barriers.

Friedman SM, Somersall L, Gill H, Gardam M, Samagh M. Division of Family and Community Medicine, University of Toronto, ON

INTRODUCTION: To assess EP knowledge, compliance with, and perceptions regarding provincial and national notifiable disease reporting requirements.METHODS: Web-based survey of CAEP membership using modified Dillman technique. EP knowledge, perceptions, and practice regarding notifiable diseases were assessed. Chi square and ancova were performed using Excel and SPSS. RESULTS: 384 (33.7%) of 1141 EPs responded, representing all Canadian provinces and a broad range of age, gender, certification, and practice setting. A test of EP knowledge of notifiable diseases resulted in mean and median scores of 70.9% and 69.2%, with significant difference in scores across provinces. 80.5% of EPs rated their knowledge of notifiable diseases as fair or poor. Only 12.9 % of EPs recognized the requirement to report suspected notifiable diseases before lab confirmation. 48.3% reported never consulting a list of notifiable diseases. Only 30.5% knew the location of a notifiable disease list in their ED. 45.9% of EPs indicated reporting ≤40% notifiable diseases. EPs identified lack of knowledge (53.1%) and time (56.8%) as major barriers to reporting. 3.2% of EPs reported that ethical concerns frequently impacted on compliance and 32.7 % reported occasional impact. Knowledge of notifiable diseases was correlated with personal estimate of knowledge (p < .001) and knowledge of location of notifiable disease list in ED (p = .007) but not with personal estimate of compliance. Knowledge was not correlated with years in practice, gender, certification, practice setting, teaching affiliation, or workload. CONCLUSIONS: EP compliance with notifiable disease reporting requirements is suboptimal. Lack of knowledge and time are identified as constraints. Key words: communicable diseases; public health

In search of the best therapy for alcohol withdrawal in the emergency department.

Gray SH, Bayoumi A, Steinhart B. Division of Emergency Medicine, University of Toronto, Toronto, ON

INTRODUCTION: Multiple studies demonstrate that symptom-triggered therapy for alcohol withdrawal treats patients more quickly and with a lower total benzodiazepine dose than scheduled treatment. However, this therapy lacks widespread adoption across North America. Indeed, a chart audit of 200 patients from two urban Canadian emergency departments (EDs) revealed that no patient received symptom-triggered treatment. The most commonly accepted and validated scale for measuring alcohol withdrawal is the Clinical Institute Withdrawal Assessment of Alcohol, Revised (CIWA-Ar). Our study uses the CIWA-Ar to direct symptom-triggered therapy in the ED, and examines whether lorazepam or diazepam is more efficacious in the efficient discharge of acute alcohol withdrawal patients.METHODS: In this randomised double-blind trial, 97 patients were randomly assigned to treatment with lorazepam or diazepam. The CIWA-Ar was used hourly to quantify the extent of withdrawal and to guide therapy. Physicians were blinded to the study drug, but chose the route (IV or oral) and the dose (high or low dose). Discharge was based on both CIWA-Ar score and clinical judgment. The primary end points were time to ED discharge and time to CIWA-Ar score less than 10. RESULTS: There was no difference between the groups in either their time to discharge from the ED (p = 0.99, relative hazard 1.00, CI 0.62-1.61), or their time to CIWA-Ar less than ten (p = 0.33, relative hazard 1.26, CI 0.79-1.99). The study was underpowered; physicians became unwilling to enroll patients as they found the CIWA-Ar too time-consuming for use in a busy ED. CONCLUSIONS: Current adoption of symptom-triggered therapy may be limited by the fact that the CIWA-Ar is lengthy and perceived as cumbersome. Further research is required to develop shorter and more efficient tools for measuring alcohol withdrawal. With better tools, the goal of widespread symptom-triggered therapy becomes achievable. Current investigations in our city are developing this concept. Key words: diazepam, lorazepam

Incidence and risk factors for methicillin-resistant Staphylococcus Aureus cellulitis in the emergency department.

Stenstrom R, Grafstein E, Fahimi J, Harris D, Hunte G, Romney M, Innes G, Christenson J. St. Paul's Hospital, Division of Emergency Medicine, University of British Columbia, Vancouver, BC

INTRODUCTION: Cellulitis is a common diagnosis in any emergency department (ED). At St Paul's Hospital, an inner ED with 60,000 patients visits/year, 7% of visits are for cellulitis. Since september 2003, there has been a marked increase in methicillin resistant staphylococcus aureus (MRSA) cellulitis incidence, and subsequent treatment with intravenous Vancomycin in our emergency department. This has important public health ramifications since Vancomycin is one of the only antibiotics to which MRSA is sensitive, and its increasing use poses a theoretical risk for the development of resistance. Also, its use in the ED is resource-intensive since it is provided every 12 hours, for many days, and requires monitoring of renal function. METHODS: Using the New Emergency Resource Database (NERD) we identified all cases of cellulitis and MRSA cellulitis between January 2003 and September 2004. Using a nested (within a cohort) case-control design, we compared risk factors between 50 incident cases MRSA cellulitis and 100 randomly selected controls, matched ± 1 month on calendar date of diagnosis, with cellulitis that was not due to MRSA. Risk factors were assessed using multivariable conditional logistic regression. RESULTS: Incidence of MRSA cellulitis increased steadily between January 2003 to September 2004 from 0.6% of cellulitis cases to 4.8% of cases. Risk factors for MRSA cellulitis include injection drug use, previously documented MRSA cellulitis, number of episodes of non-MRSA cellulitis, number of prescriptions for oral antibiotics, and previous admission to hospital (p < 0.05). CONCLUSION: Over a 20 month period, the incidence of MRSA positive cellulitis has increased eight-fold at our institution. Risk factors are injection drug use, previous episodes of MRSA cellulitis, episodes of non-MRSA cellulitis, number of prescriptions for oral antibiotics prescriptions, and previous admission to hospital. These findings have important ED and public health ramifications. Key words: injection drug use; methicillin resistance; vancomycin; cellulites

Adult epiglottitis: a five-year retrospective chart review of all cases in Hamilton.

Price IM, Preyra I, Fernandes CMB, Woolfrey K, Worster A. Emergency Medicine, McMaster University, Hamilton, ON

INTRODUCTION: Introduction of Haemophilus influenzae type B (HIB) vaccine to the immunization schedule has led to an increasing awareness of unvaccinated adults presenting with epiglottitis to the emergency department. This study examines the clinical presentations and outcomes of all adult epiglottitis cases presenting to all emergency departments in Hamilton, Ontario between 1999 and 2004.METHODS: We employed explicit protocols with defined variables, trained abstractors, standardized abstraction forms, and reviewed all adult cases of epiglottitis during a five-year period. Inter-rater agreement was measured using a kappa statistic. Summary measures are presented with 95% confidence intervals as calculated by the modified Wald method.RESULTS: Inter-rater reliability for data abstraction was κ = 1. 54 cases of epiglottitis were identified from a total of 1 million ED admissions. The mean age was 49 years (CI: 4.8-53.2) and 69% of patients were male. The three most frequently documented symptoms were sore throat (100%) (CI: 92.5-100), odynophagia (94.4%) (CI: 84.4-98.7), and inability to swallow secretions (63%) (CI: 49.7-74.7). The two most frequently documented signs were swelling of the epiglottis and/or supraglottis 98.1% (CI: 89.4-100), and tachycardia 53.7% (CI: 40.7-66.4). Organisms were isolated from blood in 11.1% of the cases. There was a white blood cell count >20,000 X 10⁹/L in only 4 of the cases (9.6%). From the 54 cases only 9 of the patients were intubated and all were safely discharged from hospital. CONCLUSIONS: Adults presenting with epiglottitis to the Emergency Department in Hamilton have good outcomes. Conservative airway management is safe in the treatment of adult epiglottitis. Key words: epiglottitis

Teaching ED teachers how to teach: a directed faculty development program.

Bandiera GW, Lee S, Foote J. Division of Emergency Medicine, University of Toronto, Toronto, ON

INTRODUCTION: There has been little research to inform faculty development around effective Emergency Medicine (EM) teaching. We sought to develop, implement, and evaluate a new EM teaching faculty development initiative. METHODS: An interactive small group half-day workshop was designed based on recent qualitative research into practical EM teaching techniques. Small group discussion topics were based on a pre-workshop needs analysis. Evaluation included a post-workshop questionnaire and a three-month follow-up survey for practice implications. RESULTS: Fifteen faculty participated. Learner-derived small group topics were: "Teaching mistakes", "Interactive teaching", and "Problem learners." Workshop component evaluations averaged 4.2/5. All 15 participants would recommend the workshop to colleagues and said they themselves would attend another similar workshop. Follow-up questionnaires were returned by 11 participants. All had successfully incorporated new strategies into their teaching, the most common being: 'Focusing on teaching points' (50%), 'Soliciting learning objectives' (60%), 'Actively seek out learners' (50%), and 'Providing focused feedback' (40%). Comfort levels for teaching were increased in 82% of respondents. CONCLUSIONS: Participants in a faculty development workshop can identify specific learning goals. Tailoring the workshop to these objectives can assure participant satisfaction, increase confidence in teaching, and lead to incorporation of new teaching strategies.Key words: medical education

Medical student skills: effectiveness of a procedures lab in teaching suturing.

Yiu S, Frank JR, Lee C, Switakowski P, Nuth J, & Weitzman B. Department of Emergency Medicine, University of Ottawa, Ottawa, ON

INTRODUCTION: Suturing is an essential skill to be acquired via undergraduate medical education. However, little has been published on effective methods of helping students acquire such skills. We set out to measure the effectiveness of a 1 hour mannequin-based procedure lab in improving objective and subjective performance in suturing as part of a new emergency medicine clerkship.METHODS: We gathered prospective observational data as part of a before and after program evaluation design. Participants included all members of initial cohort of medical students in a new emergency medicine clerkship. All students were given hands-on suturing skills training by expert instructors, which included discussions, demonstrations, online video, and practice. Using a previously validated checklist, students were rated by two expert physicians before and after the training sessions, and at the bedside by supervisors. Students were also surveyed before and after training on their self-rated competence, their number of experiences, and their satisfaction with their clerkship training. Educational impact was calculated using Cohen's d. RESULTS: 58 students participated. Cohen's d score was high for objective ratings of change in competence at 3.17. Mean difference between pre- and post-objective skills scores (95% confidence interval) was 7.37 (6.60-8.12) out of a score of 13. Cohen's d scores were also highly significant for all self-ratings of competence after training at 1.65. Overall satisfaction with the training was 4.65 on a 5-point scale.CONCLUSIONS: This procedures lab was effective in assisting medical students in acquiring essential suturing skills.Key words: medical education

Is a negative CT scan of the head and a negative lumbar puncture sufficient to rule out a subarachnoid hemorrhage?

Perry JJ, Spacek AM, Stiell IG, Forbes M, Wells GA, Mortensen M, Symington C, Fortin N. Department of Emergency Medicine, University of Ottawa, Ottawa, ON

INTRODUCTION: Current clinical practice assumes a negative CT head and a negative lumbar puncture (LP) together are adequate to rule out subarachnoid hemorrhage (SAH) in patients with acute headache. Only 2 small studies support the safety of this practice. Our objective was to determine the accuracy of a strategy of negative CT combined with a negative LP to exclude SAH. METHODS: This prospective cohort study was conducted at two academic tertiary care EDs over three years. We enrolled all patients >15 years with a complaint of non-traumatic acute (<1 hour from onset to peak) headache, normal neurological exam, and who had a CT head and an LP if the CT was negative. A negative CT was defined as no blood in the subarachnoid space. A negative LP was defined as the final tube of cerebrospinal fluid having no xanthochromia or red blood cells <5 x 106/ high-powered field. Patients were followed with a structured telephone questionnaire 6-36 months after their ED visit. Hospital records were reviewed to ensure no missed SAH. We calculated sensitivity, specificity, negative predictive value (NPV) and likelihood ratios (LR) of the strategy of CT then LP for SAH. RESULTS: There were 601 patients enrolled with 64 positive SAH. The mean patient age was 43.6 years (SD: 15.4) with 59.6% female. The following (see Table 1, Abstract 43) is the 2x2 for the strategy of CT then LP for SAH:

This CT/LP Strategy classified patients with sensitivity 100% (95% CI: 94-100), specificity 66% (95% CI: 6 2-70), NPV 100% (95% CI: 98-100), LR+ 2.936, LR- 0.0015. Hence, in an ED headache population with a 1% SAH prevalence, a patient with CT/LP strategy- has a post-test probability of SAH of only 0.002%.CONCLUSION: This is the largest prospective study evaluating the accuracy of a strategy of CT and LP to rule out SAH in alert patients presenting to the ED with an acute headache. This study validates clinical practice that a negative CT with a negative LP is sufficient to rule out SAH. Key words: diagnosis; computed tomography, lumbar puncture, subarachnoid hemorrhage

Comparison of termination-of-resuscitation guidelines for basic life support-defibrillator providers in out-of-hospital cardiac arrest.

Ong MEH, Jaffey J, Stiell IG, Nesbitt L, for the OPALS Study Group. Department of Emergency Medicine, University of Ottawa, Ottawa, ON

INTRODUCTION: Termination of Resuscitation (TOR) in the field for Out-of-Hospital Cardiac Arrest (OHCA) can reduce unnecessary transport to hospital and increase availability of EMS and ED resources for other patients. However such guidelines should be highly reliable and accurate. We sought to compare the performance of three TOR guidelines for Basic Life Support-Defibrillator (BLS-D) providers when applied to cardiac arrest patients in the Ontario Prehospital Advanced Life Support (OPALS) study. METHODS: This prospective cohort study involved all OHCA patients attended by BLS-D providers in 21 Ontario urban or suburban communities. The data analyses were conducted secondarily on these prospectively collected data. Three TOR guidelines proposed by Marsden (1995), Petrie (2001) and Verbeek (2002) were applied and contingency tables calculated to show the relationship between the rule and actual survival, area under the Receiver Operator Characteristic (ROC) Curve, and an evaluation of the sensitivity and specificity in each rule. RESULTS: From 1988 to 2003, BLS providers attended 13,684 cardiac arrest patients and 636 (4.7%) survived to hospital discharge. For the 3 TOR rules, sensitivity was: Petrie 99.8% (95% CI 99.5-100.0), Verbeek 99.5% (99.0-100.0) and Marsden 99.8% (99.5-100.0). Specificity was Petrie 9.9% (95% CI 9.4-10.4), Verbeek 52.9% (52.1-53.8), and Marsden 19.4% (18.8-20.1). Negative Predictive Value was 99.9% (95% CI = 99.8-100.0), 100.0% (95% CI = 99.9-100.0) and 100.0% (95% CI = 99.9-100.0) respectively. These rules would have resulted in field TOR in Petrie 9.4%, Verbeek 50.5% and Marsden 18.5% of cases. TOR was recommended for 1 patient (Petrie), 3 patients (Verbeek) and 1 patient (Marsden) who eventually survived.CONCLUSION: We found all three TOR rules to have high sensitivity and negative predictive value. However specificity and transport rates varied greatly. These results will be useful for EMS providers considering adoption of TOR in BLS-D systems for OHCA. Key words: cardiac arrest; resuscitation