Prospective Validation of Computed Tomography to Identify Patients at High Risk for Stroke After Transient Ischemic Attack or Minor Stroke.

BACKGROUND: Computed tomography (CT) findings of acute and chronic ischemia are associated with subsequent stroke risk in patients with transient ischemic attack. We sought to validate these associations in a large prospective cohort of patients with transient ischemic attack or minor stroke. METHODS: This prospective cohort study enrolled emergency department patients from 13 hospitals with transient ischemic attack who had CT imaging. Primary outcome was stroke within 90 days. Secondary outcomes were stroke within 2 or 7 days. CT findings were abstracted from radiology reports and classified for the presence of acute ischemia, chronic ischemia, or microangiopathy. Multivariable logistic regression was used to test associations with primary and secondary end points. RESULTS: From 8670 prospectively enrolled patients between May 2010 and May 2017, 8382 had a CT within 24 hours. From this total population, 4547 (54%) patients had evidence of acute ischemia, chronic ischemia, or microangiopathy on CT, of whom 175 had a subsequent stroke within 90 days (3.8% subsequent stroke rate; adjusted odds ratio [aOR], 2.33 [95% CI, 1.62-3.36]). This was in comparison to those with CT imaging without ischemia. Findings associated with an increased risk of stroke at 90 days were isolated acute ischemia (6.0%; aOR, 2.42 [95% CI, 1.03-5.66]), acute ischemia with microangiopathy (10.7%; aOR, 3.34 [95% CI, 1.57-7.14]), chronic ischemia with microangiopathy (5.2%; aOR, 1.83 [95% CI, 1.34-2.50]), and acute ischemia with chronic ischemia and microangiopathy (10.9%; aOR, 3.49 [95% CI, 1.54-7.91]). Acute ischemia with chronic ischemia and microangiopathy were most strongly associated with subsequent stroke within 2 days (aOR, 4.36 [95% CI, 1.31-14.54]) and 7 days (aOR, 4.50 [95% CI, 1.73-11.69]). CONCLUSIONS: In patients with transient ischemic attack or minor stroke, CT evidence of acute ischemia with chronic ischemia or microangiopathy significantly increases the risk of subsequent stroke within 90 days of index visit. The combination of all 3 findings results in the greatest early risk.

Electrical versus pharmacological cardioversion for emergency department patients with acute atrial fibrillation (RAFF2): a partial factorial randomised trial.

BACKGROUND: Acute atrial fibrillation is the most common arrythmia treated in the emergency department. Our primary aim was to compare conversion to sinus rhythm between pharmacological cardioversion followed by electrical cardioversion (drug-shock), and electrical cardioversion alone (shock-only). Our secondary aim was to compare the effectiveness of two pad positions for electrical cardioversion. METHODS: We did a partial factorial trial of two protocols for patients with acute atrial fibrillation at 11 academic hospital emergency departments in Canada. We enrolled adult patients with acute atrial fibrillation. Protocol 1 was a randomised, blinded, placebo-controlled comparison of attempted pharmacological cardioversion with intravenous procainamide (15 mg/kg over 30 min) followed by electrical cardioversion if necessary (up to three shocks, each of ≥200 J), and placebo infusion followed by electrical cardioversion. For patients having electrical cardioversion, we used Protocol 2, a randomised, open-label, nested comparison of anteroposterior versus anterolateral pad positions. Patients were randomly assigned (1:1, stratified by study site) for Protocol 1 by on-site research personnel using an online electronic data capture system. Randomisation for Protocol 2 occurred 30 min after drug infusion for patients who had not converted and was stratified by site and Protocol 1 allocation. Patients and all research and emergency department staff were masked to treatment allocation for Protocol 1. The primary outcome was conversion to normal sinus rhythm for at least 30 min at any time after randomisation and up to a point immediately after three shocks. Protocol 1 was analysed by intention to treat and Protocol 2 excluded patients who did not receive electrical cardioversion. This study is registered at ClinicalTrials.gov, number NCT01891058. FINDINGS: Between July 18, 2013, and Oct 17, 2018, we enrolled 396 patients, and none were lost to follow-up. In the drug-shock group (n=204), conversion to sinus rhythm occurred in 196 (96%) patients and in the shock-only group (n=192), conversion occurred in 176 (92%) patients (absolute difference 4%; 95% CI 0-9; p=0·07). The proportion of patients discharged home was 97% (n=198) versus 95% (n=183; p=0·60). 106 (52%) patients in the drug-shock group converted after drug infusion only. No patients had serious adverse events in follow-up. The different pad positions in Protocol 2 (n=244), had similar conversions to sinus rhythm (119 [94%] of 127 in anterolateral group vs 108 [92%] of 117 in anteroposterior group; p=0·68). INTERPRETATION: Both the drug-shock and shock-only strategies were highly effective, rapid, and safe in restoring sinus rhythm for patients in the emergency department with acute atrial fibrillation, avoiding the need for return to hospital. The drug infusion worked for about half of patients and avoided the resource intensive procedural sedation required for electrical cardioversion. We also found no significant difference between the anterolateral and anteroposterior pad positions for electrical cardioversion. Immediate rhythm control for patients in the emergency department with acute atrial fibrillation leads to excellent outcomes. FUNDING: Heart and Stroke Foundation of Canada and the Canadian Institutes of Health Research.

Predicting mortality from acetaminophen poisoning shortly after hospital presentation.

AIMS: Early identification of patients likely to die after acetaminophen (APAP) poisoning remains challenging. We sought to compare the sensitivity and time to fulfilment (latency) of established prognostic criteria. METHODS: Three physician toxicologists independently classified every in-hospital death associated with APAP overdose from eight large Canadian cities over three decades using the Relative Contribution to Fatality scale from the American Association of Poison Control Centres. The sensitivity and latency were calculated for each of the following criteria: King's College Hospital (KCH), Model for End Stage Liver Disease (MELD) ≥33, lactate ≥3.5 mmol/L, phosphate ≥1.2 mmol/L 48+ hours post-ingestion, as well as combinations thereof. RESULTS: A total of 162 in-hospital deaths were classified with respect to APAP as follows: 26 Undoubtedly, 40 Probably, 27 Contributory, 14 Probably not, 25 Clearly not, and 30 Unknown. Cases from the first three classes (combined into n = 93 "APAP deaths") typically presented with supratherapeutic APAP concentrations, hepatotoxicity, acidaemia, coagulopathy and/or encephalopathy, and began antidotal treatment a median of 12 hours (IQR 3.4-30 h) from the end of ingestion. Among all patients deemed "APAP deaths", meeting either KCH or lactate criteria demonstrated the highest sensitivity (94%; 95% CI 86-98%), and the shortest latency from hospital arrival to criterion fulfilment (median 4.2 h; IQR 1.0-16 h). In comparison, the MELD criterion demonstrated a substantially lower sensitivity (55%; 43-66%) and longer latency (52 h; 4.4-∞ h, where "∞" denotes death prior to criterion becoming positive). CONCLUSIONS: Meeting either KCH or serum lactate criteria identifies most patients who die from acetaminophen poisoning at or shortly after hospital presentation.

Intravenous Haloperidol Versus Ondansetron for Cannabis Hyperemesis Syndrome (HaVOC): A Randomized, Controlled Trial.

STUDY OBJECTIVE: Little is known about the cause or optimal treatment of hyperemesis in habitual cannabis users. Anecdotal evidence supports the use of haloperidol over traditional antiemetics for this newly recognized disorder. We compare haloperidol with ondansetron for cannabis hyperemesis syndrome. METHODS: We randomized cannabis users with active emesis to either haloperidol (with a nested randomization to either 0.05 or 0.1 mg/kg) or ondansetron 8 mg intravenously in a triple-blind fashion. The primary outcome was the reduction from baseline in abdominal pain and nausea (each measured on a 10-cm visual analog scale) at 2 hours after treatment. Although the trial allowed for crossover, the primary analysis used only the first treatment period because few subjects crossed over. RESULTS: We enrolled 33 subjects, of whom 30 (16 men, aged 29 years [SD 11 years] using 1.5 g/day [SD 0.9 g/day] since age 19 years [SD 2 years]) received at least 1 treatment (haloperidol 13, ondansetron 17). Haloperidol at either dose was superior to ondansetron (difference 2.3 cm [95% confidence interval 0.6 to 4.0 cm]; P=.01), with similar improvements in both pain and nausea, as well as less use of rescue antiemetics (31% versus 59%; difference -28% [95% confidence interval -61% to 13%]) and shorter time to emergency department (ED) departure (3.1 hours [SD 1.7] versus 5.6 hours [SD 4.5]; difference 2.5 hours [95% confidence interval 0.1 to 5.0 hours]; P=.03). There were 2 return visits for acute dystonia, both in the higher-dose haloperidol group. CONCLUSION: In this clinical trial, haloperidol was superior to ondansetron for the acute treatment of cannabis-associated hyperemesis. The efficacy of haloperidol over ondansetron provides insight into the pathophysiology of this now common diagnosis in many EDs.

Adverse Events Among Emergency Department Patients With Cardiovascular Conditions: A Multicenter Study.

STUDY OBJECTIVE: We aim to determine incidence and type of adverse events (adverse outcomes related to emergency care) among emergency department (ED) patients discharged with recent-onset atrial fibrillation, acute heart failure, and syncope. METHODS: This 5-year prospective cohort study included high-acuity adult patients discharged with the 3 sentinel diagnoses from 6 tertiary care Canadian EDs. We screened all ED visits for eligibility and performed telephone interviews 14 days postdischarge to identify flagged outcomes: death, hospital admission, return ED visit, health care provider visit, and new or worsening symptoms. We created case summaries describing index ED visit and flagged outcomes, and trained emergency physicians reviewed case summaries to identify adverse events. We reported adverse event incidence and rates with 95% confidence intervals and contributing factor themes. RESULTS: Among 4,741 subjects (mean age 70.2 years; 51.2% men), we observed 170 adverse events (3.6 per 100 patients; 95% confidence interval 3.1 to 4.2). Patients discharged with acute heart failure were most likely to experience adverse events (5.3%), followed by those with atrial fibrillation (2.0%) and syncope (0.8%). We noted variation in absolute adverse event rates across sites from 0.7 to 6.0 per 100 patients. The most common adverse event types were management issues, diagnostic issues, and unsafe disposition decisions. Frequent contributing factor themes included failure to recognize underlying causes and inappropriate management of dual diagnoses. CONCLUSION: Among adverse events after ED discharge for patients with these 3 sentinel cardiovascular diagnoses, we identified quality improvement opportunities such as strengthening dual diagnosis detection and evidence-based clinical practice guideline adherence.

Does N-Terminal Pro-B-Type Natriuretic Peptide Improve the Risk Stratification of Emergency Department Patients With Syncope?

BACKGROUND: Studies have reported that natriuretic peptides provide prognostic information for emergency department (ED) syncope. OBJECTIVE: To evaluate whether adding N-terminal pro-B-type natriuretic peptide (NT-proBNP) to the Canadian Syncope Risk Score (CSRS) improves prediction of 30-day serious adverse events (SAEs). DESIGN: Prospective cohort study. SETTING: 6 EDs in 2 Canadian provinces. PARTICIPANTS: 1452 adult ED patients with syncope. INTERVENTION: Serum NT-proBNP was measured locally at 1 site and batch processed at a central laboratory from other sites. The concentrations were not available to treating physicians or for adjudication of outcomes. MEASUREMENTS: An adjudicated composite outcome of 30-day SAEs, including death and cardiac (arrhythmic and nonarrhythmic) and noncardiac events. RESULTS: Of 1452 patients enrolled, 152 (10.5% [95% CI, 9.0% to 12.1%]) had 30-day SAEs, 57 (3.9%) of which were identified after the index ED disposition. Serum NT-proBNP concentrations were significantly higher among patients with SAEs than those without them (median, 626.5 ng/L vs. 81 ng/L; P < 0.001). Adding NT-proBNP values to the CSRS did not significantly improve prognostication (c-statistic, 0.89 and 0.90; P = 0.12 for difference), regardless of SAE subgroup or whether the SAE was identified after the index ED visit. The net reclassification index shows that NT-proBNP would have correctly reclassified 3% of patients with SAEs at the expense of incorrectly reclassifying 2% of patients without SAEs. LIMITATIONS: Our study was powered to detect a 3% difference in the area under the curve. The heterogeneity of outcomes and robust baseline discrimination by the CSRS will make improvements challenging. CONCLUSION: Although serum NT-proBNP concentrations were generally much higher among ED patients with syncope who had a 30-day SAE, this blood test added little new information to the CSRS. Routine use of NT-proBNP for ED syncope prognostication is not recommended. PRIMARY FUNDING SOURCE: Physicians' Services Incorporated Foundation, Canadian Institutes of Health Research, and The Ottawa Hospital Academic Medical Organization.

Duration of Electrocardiographic Monitoring of Emergency Department Patients With Syncope.

BACKGROUND: The optimal duration of cardiac rhythm monitoring after emergency department (ED) presentation for syncope is poorly described. We sought to describe the incidence and time to arrhythmia occurrence to inform decisions regarding duration of monitoring based on ED risk stratification. METHODS: We conducted a prospective cohort study with enrolled adult patients (≥16 years old) presenting within 24 hours of syncope at 6 EDs. We collected baseline characteristics, time of syncope and ED arrival, and the Canadian Syncope Risk Score (CSRS) risk category. We followed subjects for 30 days, and our adjudicated primary outcome was serious arrhythmic conditions (arrhythmias, interventions for arrhythmias, and unexplained death). After excluding patients with an obvious serious condition on ED presentation and those with missing CSRS predictors, we used Kaplan-Meier analysis to describe the time to serious arrhythmic outcomes. RESULTS: A total of 5581 patients (mean age, 53.4 years; 54.5% females; 11.6% hospitalized) were available for analysis, including 346 (6.2%) for whom the 30-day follow-up was incomplete and who were censored at the last follow-up time. A total of 417 patients (7.5%) experienced serious outcomes, 207 of which (3.7%; 95% CI, 3.3%-4.2%) were arrhythmic (161 arrhythmias, 30 cardiac device implantations, 16 unexplained deaths). Overall, 4123 (73.9%) were classified as CSRS low risk, 1062 (19.0%) medium risk, and 396 (7.1%) high risk. The CSRS accurately stratified subjects as low risk (0.4% risk for 30-day arrhythmic outcome), medium risk (8.7% risk), and high risk (25.3% risk). One-half of arrhythmic outcomes were identified within 2 hours of ED arrival in low-risk patients and within 6 hours in medium- and high-risk patients, and the residual risk after these cut points were 0.2% for low-risk, 5.0% for medium-risk, and 18.1% for high-risk patients. Overall, 91.7% of arrhythmic outcomes among medium- and high-risk patients, including all ventricular arrhythmias, were identified within 15 days. None of the low-risk patients experienced ventricular arrhythmia or unexplained death, whereas 0.9% of medium-risk patients and 6.3% of high-risk patients experienced them ( P<0.0001). CONCLUSIONS: Serious underlying arrhythmia was often identified within the first 2 hours of ED arrival for CSRS low-risk patients and within 6 hours for CSRS medium- and high-risk patients. Outpatient cardiac rhythm monitoring for 15 days for selected medium-risk patients and all high-risk patients discharged from the hospital should also be considered.

Prospective Implementation of the Ottawa Subarachnoid Hemorrhage Rule and 6-Hour Computed Tomography Rule.

Background and Purpose- The Ottawa subarachnoid hemorrhage (SAH) rule identifies patients with headache requiring no testing for SAH, while the 6-hour computed tomography (CT) rule guides when to forgo a lumbar puncture. Our objectives were to: (1) estimate the clinical impact of the Ottawa SAH rule and the 6-hour-CT rule on testing rates (ie, CT, lumbar puncture, CT angiography); (2) validate the 6-hour-CT rule for SAH when applied prospectively in a new cohort of patients. Methods- We conducted a multicenter prospective before/after implementation study from 2011 to 2016 with 6 months follow-up at 6 tertiary-care Canadian Academic Emergency Departments. Consecutive alert, neurologically intact adults with headache were included. For intervention period, physicians were given a 1-hour lecture, pocket cards, posters were installed, and physicians indicated Ottawa SAH rule criteria when ordering CTs. SAH was defined by blood on CT, xanthochromia in cerebrospinal fluid, or >1×106/L red blood cells in cerebrospinal fluid with aneurysm. Results- We enrolled 3672 patients, 1743 before and 1929 after implementation, including 188 with SAH. Proportions undergoing CT was unchanged (88.0% versus 87.5%; P=0.643). Lumbar puncture use decreased (38.9% versus 25.9%; P<0.0001). Additional testing following CT (ie, lumbar puncture or CT angiography) decreased (51.3% versus 42.2%; P<0.0001). Admissions declined (9.8% versus 7.4%; P=0.011). Mean emergency department stay was unchanged (6.3±4.0 versus 6.4±4.2 hours; P=0.685). The Ottawa SAH rule was 100% (95% CI, 98.1%-100%) sensitive, and the 6-hour-CT rule was 95.5% (95% CI, 89.8-98.5) sensitive for SAH. The 6-hour-CT rule missed 5 SAHs: 1 radiology misread, 2 incidental aneurysms, 1 nonaneurysmal cause, and 1 profoundly anemic patient. Conclusions- The Ottawa SAH rule and the 6-hour-CT rule are highly sensitive and can be used routinely when SAH is considered in patients with headache. Implementing both rules was associated with a meaningful decrease in testing and admissions to hospital.

Benefit of hospital admission for detecting serious adverse events among emergency department patients with syncope: a propensity-score-matched analysis of a multicentre prospective cohort.

BACKGROUND: The benefit of hospital admission after emergency department evaluation for syncope is unclear. We sought to determine the association between hospital admission and detection of serious adverse events, and whether this varied according to the Canadian Syncope Risk Score (CSRS). METHODS: We conducted a secondary analysis of a multicentre prospective cohort of patients assessed in the emergency department for syncope. We compared patients admitted to hospital and discharged patients, using propensity scores to match 1:1 for risk of a serious adverse event. The primary outcome was detection of a serious adverse event in hospital for admitted patients or within 30 days after emergency department disposition for discharged patients. RESULTS: We included 8183 patients, of whom 743 (9.1%) were admitted; 658/743 (88.6%) were matched. Admitted patients had higher odds of detection of a serious adverse event (odds ratio [OR] 5.0, 95% confidence interval [CI] 3.3-7.4), nonfatal arrhythmia (OR 5.1, 95% CI 2.9-8.8) and nonarrhythmic serious adverse event (OR 6.3, 95% CI 2.9-13.5). There were no significant differences between the 2 groups in death (OR 1.0, 95% CI 0.4-2.7) or detection of ventricular arrhythmia (OR 2.0, 95% CI 0.7-6.0). Differences between admitted and discharged patients in detection of serious adverse events were greater for those with a CSRS indicating medium to high risk (p = 0.04). INTERPRETATION: Patients with syncope were more likely to have serious adverse events identified within 30 days if they were admitted to hospital rather than discharged from the emergency department. However, the benefit of hospital admission is low for patients at low risk of a serious adverse event.

ST-elevation in ethylene glycol toxicity mimicking myocardial infarction.

Electrocardiographic changes due to ethylene glycol toxicity are described in a 37-year-old woman who presented with intentional overdose. She received prompt treatment with dialysis and fomepizole, which reversed profound metabolic acidosis. ST-elevation in leads I, aVL, and aVR were observed 87 h after admission along with diffuse repolarization abnormalities. Coronary angiography found no evidence of coronary artery disease, and echocardiogram revealed normal left ventricle size and a mildly hypokinetic basal inferior wall. Diffuse repolarization abnormalities persisted for several days. Review of literature supports the diagnosis of myocarditis induced by toxic metabolites of ethylene glycol in context of hepatic and renal failure.

Outcomes After Recurrent Intentional Methanol Exposures Not Treated With Alcohol Dehydrogenase Inhibitors Or Hemodialysis.

BACKGROUND: Relying on a treatment threshold for methanol poisoning of 20 mg/dL (6.2 mmol/L) as a stand-alone criterion may lead to unnecessary and invasive treatment because it is likely too conservative, especially for patients with repeated, intentional methanol exposures. OBJECTIVE: We investigated how often patients with recurrent intentional methanol exposures above this threshold developed biochemical or overt clinical toxicity despite not being treated with either an alcohol dehydrogenase inhibitor (ADHi) or hemodialysis. METHODS: We identified patients with ≥3 methanol-related emergency visits from 2002 to 2015 and selected every visit in which neither ADHi nor hemodialysis were administered despite serum methanol >20 mg/dL but neither metabolic acidosis nor end organ toxicity at presentation. The primary outcome was the incidence of visual deterioration or death. RESULTS: Four patients accounted for the 17 visits that met inclusion criteria. All exposures were intentional substance misuse, and 7 of 17 were via inhalation (i.e., huffing). Initial methanol concentrations ranged from 22 mg/dL to 35 mg/dL (7-11 mmol/L). Four of these 17 visits had undetectable initial ethanol concentrations at presentation, including 1 with an initial methanol concentration of 35 mg/dL. No patients developed visual deterioration, and all were known to have survived the exposure. CONCLUSION: Following recurrent, intentional methanol exposure, isolated serum methanol concentrations as high as 35 mg/dL (11 mmol/L) appear to be well-tolerated without treatment in the absence of metabolic acidosis or end-organ toxicity. To better define the methanol treatment threshold, prospective studies are warranted in which patients are followed closely while fomepizole is withheld.

Prevalence of Pulmonary Embolism Among Emergency Department Patients With Syncope: A Multicenter Prospective Cohort Study.

STUDY OBJECTIVE: The prevalence of pulmonary embolism among patients with syncope is understudied. In accordance with a recent study with an exceptionally high pulmonary embolism prevalence, some advocate evaluating all syncope patients for pulmonary embolism, including those with another clear cause for their syncope. We seek to evaluate the pulmonary embolism prevalence among emergency department (ED) patients with syncope. METHODS: We combined data from 2 large prospective studies enrolling adults with syncope from 17 EDs in Canada and the United States. Each study collected the results of pulmonary embolism-related investigations (ie, D-dimer, ventilation-perfusion scan, or computed tomography [CT] pulmonary angiography) and 30-day adjudicated outcomes: pulmonary embolism or nonpulmonary embolism outcome (arrhythmia, myocardial infarction, serious hemorrhage, and death). RESULTS: Of the 9,374 patients enrolled, 9,091 (97.0%; median age 66 years, 51.9% women) with 30-day follow-up were analyzed: 547 (6.0%) were evaluated for pulmonary embolism (278 [3.1%] had D-dimer, 39 [0.4%] had ventilation-perfusion scan, and 347 [3.8%] had CT pulmonary angiography). Overall, 874 patients (9.6%) experienced 30-day serious outcomes: 818 patients (9.0%) with nonpulmonary embolism serious outcomes and 56 (prevalence 0.6%; 95% confidence interval 0.5% to 0.8%) with pulmonary embolism (including 8 [0.2%] out of 3521 patients diagnosed during the index hospitalization and 7 [0.1%] diagnosed after the index visit). Eighty-six patients (0.9%) died, and 4 deaths (0.04%) were related to pulmonary embolism. Only 11 patients (0.1%) with a nonpulmonary embolism serious condition had a concomitant pulmonary embolism. CONCLUSION: The prevalence of pulmonary embolism is very low among ED patients with syncope, including those hospitalized after syncope. Although an underlying pulmonary embolism may cause syncope, clinicians should be cautious about indiscriminate investigations for pulmonary embolism.

Application of outpatient cardiac testing among emergency department patients with syncope.

OBJECTIVES: 2.6% of ED syncope patients will suffer cardiac serious adverse events (SAEs) within 30 days of disposition, and outpatient cardiac testing can improve patient safety. The objective is to determine whether outpatient cardiac testing for ED syncope patients is being appropriately ordered after discharge. To this end, we describe the proportion of high-risk and non-high (low and medium)-risk ED syncope patients as per the Canadian Syncope Risk Score (CSRS) who have a SAE after ED discharge, and the proportion referred for outpatient cardiac testing. METHODS: Our multicentre prospective cohort study enrolled adult syncope patients between 2010 and 2014 in five academic EDs. We collected patient characteristics, disposition, CSRS predictors, outpatient referrals and testing results (Holter, echocardiography), and 30-day adjudicated SAE (death due to unknown/cardiac cause, myocardial infarction, arrhythmia and structural heart disease). We used descriptive statistics (mean, SD) to report our results. RESULTS: Of 3584 enrolled patients (mean age 50.9 years, 57.7% women), 800 patients (22.3%) received an outpatient referral. Of these 800 patients, 40.3% of the non-high-risk patients (305/756) and 54.5% of the high-risk patients (24/44) received outpatient cardiac testing. Of all patients who received cardiac testing, five (1.5%; 95% CI 0.6% to 3.5%) suffered outpatient SAE (60.0% arrhythmias). Of all patients who did not receive cardiac testing, four patients (0.9%; 95% CI 0.3% to 2.2%) suffered SAE (all arrhythmias). Of the 20 (45.5%) high-risk patients who did not receive testing, two patients (10.0%; 95% CI 2.8% to 30.1%) suffered arrhythmias outside the hospital, while among the 451 (59.7%) non-high-risk patients, only two (0.4%; 95% CI 0.1% to 1.6%) suffered outpatient arrhythmias. CONCLUSION: Outpatient cardiac testing is largely underused, especially among high-risk ED syncope patients. Better guidelines for outpatient cardiac testing are needed, as the practice is highly variable and mismatched with patient risk.

Impact of Expanding the Prehospital Stroke Bypass Time Window in a Large Geographic Region.

BACKGROUND AND PURPOSE: The Ontario Acute Stroke Medical Redirect Paramedic Protocol (ASMRPP) was revised to allow paramedics to bypass to designated stroke centers if total transport time would be <2 hours and total time from symptom onset <3.5 hours. We sought to evaluate the impact and safety of implementing the Revised ASMRPP. METHODS: We conducted a 12-month implementation study involving prehospital patients presenting with possible stroke symptoms. A total of 1317 basic and advanced life support paramedics, of 9 land services in 10 rural counties and 5 cities, used the Revised ASMRPP to take appropriate patients directly to 6 designated stroke centers. RESULTS: We enrolled 1277 patients with 98.8% paramedic compliance in form completion. Of these, 755 (61.2%) met the redirect criteria and had these characteristics: mean age 72.1 (range 16-101), male 51.1%, mean time scene to hospital 16.7 minutes (range 0-92). Paramedics demonstrated excellent interobserver agreement (κ, 0.94; 95% confidence interval, 0.91-0.96) and 97.9% accuracy in interpretation of the Revised ASMRPP. Prehospital adverse events occurred in 14.7% of patients, but few were life-threatening. Overall, 71.4% of 755 cases had a stroke code activated at the hospital and 23.2% received thrombolysis. For the 189 potential stroke patients picked up in 1 city, the ASMRPP classified thrombolysis administration with sensitivity 100% and specificity 37.3% and a final diagnosis of stroke, with sensitivity 86.1% and specificity 41.9%. CONCLUSIONS: In a large urban-rural area with 9 paramedic services, we demonstrated accurate, safe, and effective implementation of the Revised ASMRPP. These revisions will allow more patients with stroke to benefit from early treatment.

Validation of the Ottawa Subarachnoid Hemorrhage Rule in patients with acute headache.

BACKGROUND: We previously derived the Ottawa Subarachnoid Hemorrhage Rule to identify subarachnoid hemorrhage (SAH) in patients with acute headache. Our objective was to validate the rule in a new cohort of consecutive patients who visited an emergency department. METHODS: We conducted a multicentre prospective cohort study at 6 university-affiliated tertiary-care hospital emergency departments in Canada from January 2010 to January 2014. We included alert, neurologically intact adult patients with a headache peaking within 1 hour of onset. Treating physicians in the emergency department explicitly scored the rule before investigations were started. We defined subarachnoid hemorrhage as detection of any of the following: subarachnoid blood visible upon computed tomography of the head (from the final report by the local radiologist); xanthochromia in the cerebrospinal fluid (by visual inspection); or the presence of erythrocytes (> 1 × 106/L) in the final tube of cerebrospinal fluid, with an aneurysm or arteriovenous malformation visible upon cerebral angiography. We calculated sensitivity and specificity of the Ottawa SAH Rule for detecting or ruling out subarachnoid hemorrhage. RESULTS: Treating physicians enrolled 1153 of 1743 (66.2%) potentially eligible patients, including 67 with subarachnoid hemorrhage. The Ottawa SAH Rule had 100% sensitivity (95% confidence interval [CI] 94.6%-100%) with a specificity of 13.6% (95% CI 13.1%-15.8%), whereas neuroimaging rates remained similar (about 87%). INTERPRETATION: We found that the Ottawa SAH Rule was sensitive for identifying subarachnoid hemorrhage in otherwise alert and neurologically intact patients. We believe that the Ottawa SAH Rule can be used to rule out this serious diagnosis, thereby decreasing the number of cases missed while constraining rates of neuroimaging.

Measuring physician cognitive load: validity evidence for a physiologic and a psychometric tool.

In general, researchers attempt to quantify cognitive load using physiologic and psychometric measures. Although the construct measured by both of these metrics is thought to represent overall cognitive load, there is a paucity of studies that compares these techniques to one another. The authors compared data obtained from one physiologic tool (pupillometry) to one psychometric tool (Paas scale) to explore whether they actually measured the construct of cognitive load as purported. Thirty-two participants with a range of resuscitation medicine experience and expertise completed resuscitation-medicine based multiple-choice-questions as well as arithmetic questions. Cognitive load, as measured by both tools, was found to be higher for the more difficult questions as well as for questions that were answered incorrectly (p < 0.001). The group with the least medical experience had higher cognitive load than both the intermediate and experienced groups when answering domain-specific questions (p = 0.023 and p = 0.003 respectively for the physiologic tool; p = 0.006 and p < 0.001 respectively for the psychometric tool). There was a strong positive correlation (Spearman's ρ = 0.827, p < 0.001 for arithmetic questions; Spearman's ρ = 0.606, p < 0.001 for medical questions) between the two cognitive load measurement tools. These findings support the validity argument that both physiologic and psychometric metrics measure the construct of cognitive load.

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.