Development and validation of self-monitoring auto-updating prognostic models of survival for hospitalized COVID-19 patients

Clinical prognostic models can assist patient care decisions. However, their performance can drift over time and location, necessitating model monitoring and updating. Despite rapid and significant changes during the pandemic, prognostic models for COVID-19 patients do not currently account for these drifts. We develop a framework for continuously monitoring and updating prognostic models and apply it to predict 28-day survival in COVID-19 patients. We use demographic, laboratory, and clinical data from electronic health records of 34912 hospitalized COVID-19 patients from March 2020 until May 2022 and compare three modeling methods. Model calibration performance drift is immediately detected with minor fluctuations in discrimination. The overall calibration on the prospective validation cohort is significantly improved when comparing the dynamically updated models against their static counterparts. Our findings suggest that, using this framework, models remain accurate and well-calibrated across various waves, variants, race and sex and yield positive net-benefits.

A method to quantify autonomic nervous system function in healthy, able-bodied individuals

BACKGROUND

The autonomic nervous system (ANS) maintains physiological homeostasis in various organ systems via parasympathetic and sympathetic branches. ANS function is altered in common diffuse and focal conditions and heralds the beginning of environmental and disease stresses. Reliable, sensitive, and quantitative biomarkers, first defined in healthy participants, could discriminate among clinically useful changes in ANS function. This framework combines controlled autonomic testing with feature extraction during physiological responses.

METHODS

Twenty-one individuals were assessed in two morning and two afternoon sessions over two weeks. Each session included five standard clinical tests probing autonomic function: squat test, cold pressor test, diving reflex test, deep breathing, and Valsalva maneuver. Noninvasive sensors captured continuous electrocardiography, blood pressure, breathing, electrodermal activity, and pupil diameter. Heart rate, heart rate variability, mean arterial pressure, electrodermal activity, and pupil diameter responses to the perturbations were extracted, and averages across participants were computed. A template matching algorithm calculated scaling and stretching features that optimally fit the average to an individual response. These features were grouped based on test and modality to derive sympathetic and parasympathetic indices for this healthy population.

RESULTS

A significant positive correlation (p = 0.000377) was found between sympathetic amplitude response and body mass index. Additionally, longer duration and larger amplitude sympathetic and longer duration parasympathetic responses occurred in afternoon testing sessions; larger amplitude parasympathetic responses occurred in morning sessions.

CONCLUSIONS

These results demonstrate the robustness and sensitivity of an algorithmic approach to extract multimodal responses from standard tests. This novel method of quantifying ANS function can be used for early diagnosis, measurement of disease progression, or treatment evaluation.

TRIAL REGISTRATION

This study registered with Clinicaltrials.gov , identifier NCT04100486 . Registered September 24, 2019, https://www.clinicaltrials.gov/ct2/show/NCT04100486 .

Barriers to the Use of Clinical Decision Support for the Evaluation of Pulmonary Embolism: Qualitative Interview Study

BACKGROUND

Clinicians often disregard potentially beneficial clinical decision support (CDS).

OBJECTIVE

In this study, we sought to explore the psychological and behavioral barriers to the use of a CDS tool.

METHODS

We conducted a qualitative study involving emergency medicine physicians and physician assistants. A semistructured interview guide was created based on the Capability, Opportunity, and Motivation-Behavior model. Interviews focused on the barriers to the use of a CDS tool built based on Wells' criteria for pulmonary embolism to assist clinicians in establishing pretest probability of pulmonary embolism before imaging.

RESULTS

Interviews were conducted with 12 clinicians. Six barriers were identified, including (1) Bayesian reasoning, (2) fear of missing a pulmonary embolism, (3) time pressure or cognitive load, (4) gestalt includes Wells' criteria, (5) missed risk factors, and (6) social pressure.

CONCLUSIONS

Clinicians highlighted several important psychological and behavioral barriers to CDS use. Addressing these barriers will be paramount in developing CDS that can meet its potential to transform clinical care.

The Cholinergic Drug Galantamine Alleviates Oxidative Stress Alongside Anti-inflammatory and Cardio-Metabolic Effects in Subjects With the Metabolic Syndrome in a Randomized Trial

Background: The metabolic syndrome (MetS) is an obesity-associated disorder of pandemic proportions and limited treatment options. Oxidative stress, low-grade inflammation and altered neural autonomic regulation, are important components and drivers of pathogenesis. Galantamine, an acetylcholinesterase inhibitor and a cholinergic drug that is clinically-approved (for Alzheimer's disease) has been implicated in neural cholinergic regulation of inflammation in several conditions characterized with immune and metabolic derangements. Here we examined the effects of galantamine on oxidative stress in parallel with inflammatory and cardio-metabolic parameters in subjects with MetS. Trial Design and Methods: The effects of galantamine treatment, 8 mg daily for 4 weeks or placebo, followed by 16 mg daily for 8 weeks or placebo were studied in randomly assigned subjects with MetS (n = 22 per group) of both genders. Oxidative stress, including superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase activities, lipid and protein peroxidation, and nitrite levels were analyzed before and at the end of the treatment. In addition, plasma cytokine and adipokine levels, insulin resistance (HOMA-IR) and other relevant cardio-metabolic indices were analyzed. Autonomic regulation was also examined by heart rate variability (HRV) before treatment, and at every 4 weeks of treatment. Results: Galantamine treatment significantly increased antioxidant enzyme activities, including SOD [+1.65 USOD/mg protein, [95% CI 0.39-2.92], P = 0.004] and CAT [+0.93 nmol/mg, [95% CI 0.34-1.51], P = 0.01], decreased lipid peroxidation [thiobarbituric acid reactive substances [log scale 0.72 pmol/mg, [95% CI 0.46-1.07], P = 0.05], and systemic nitrite levels [log scale 0.83 μmol/mg protein, [95% CI 0.57-1.20], P = 0.04] compared with placebo. In addition, galantamine significantly alleviated the inflammatory state and insulin resistance, and decreased the low frequency/high frequency ratio of HRV, following 8 and 12 weeks of drug treatment. Conclusion: Low-dose galantamine alleviates oxidative stress, alongside beneficial anti-inflammatory, and metabolic effects, and modulates neural autonomic regulation in subjects with MetS. These findings are of considerable interest for further studies with the cholinergic drug galantamine to ameliorate MetS.

Let Sleeping Patients Lie, avoiding unnecessary overnight vitals monitoring using a clinically based deep-learning model

Impaired sleep for hospital patients is an all too common reality. Sleep disruptions due to unnecessary overnight vital sign monitoring are associated with delirium, cognitive impairment, weakened immunity, hypertension, increased stress, and mortality. It is also one of the most common complaints of hospital patients while imposing additional burdens on healthcare providers. Previous efforts to forgo overnight vital sign measurements and improve patient sleep used providers’ subjective stability assessment or utilized an expanded, thus harder to retrieve, set of vitals and laboratory results to predict overnight clinical risk. Here, we present a model that incorporates past values of a small set of vital signs and predicts overnight stability for any given patient-night. Using data obtained from a multi-hospital health system between 2012 and 2019, a recurrent deep neural network was trained and evaluated using ~2.3 million admissions and 26 million vital sign assessments. The algorithm is agnostic to patient location, condition, and demographics, and relies only on sequences of five vital sign measurements, a calculated Modified Early Warning Score, and patient age. We achieved an area under the receiver operating characteristic curve of 0.966 (95% confidence interval [CI] 0.956–0.967) on the retrospective testing set, and 0.971 (95% CI 0.965–0.974) on the prospective set to predict overnight patient stability. The model enables safe avoidance of overnight monitoring for ~50% of patient-nights, while only misclassifying 2 out of 10,000 patient-nights as stable. Our approach is straightforward to deploy, only requires regularly obtained vital signs, and delivers easily actionable clinical predictions for a peaceful sleep in hospitals.

Machine learning to assist clinical decision-making during the COVID-19 pandemic

BACKGROUND

The number of cases from the coronavirus disease 2019 (COVID-19) global pandemic has overwhelmed existing medical facilities and forced clinicians, patients, and families to make pivotal decisions with limited time and information.

MAIN BODY

While machine learning (ML) methods have been previously used to augment clinical decisions, there is now a demand for "Emergency ML." Throughout the patient care pathway, there are opportunities for ML-supported decisions based on collected vitals, laboratory results, medication orders, and comorbidities. With rapidly growing datasets, there also remain important considerations when developing and validating ML models.

CONCLUSION

This perspective highlights the utility of evidence-based prediction tools in a number of clinical settings, and how similar models can be deployed during the COVID-19 pandemic to guide hospital frontlines and healthcare administrators to make informed decisions about patient care and managing hospital volume.

Development and Validation of a Survival Calculator for Hospitalized Patients with COVID-19

BACKGROUND

Chinese studies reported predictors of severe disease and mortality associated with coronavirus disease 2019 (COVID-19). A generalizable and simple survival calculator based on data from US patients hospitalized with COVID-19 has not yet been introduced.

OBJECTIVE

Develop and validate a clinical tool to predict 7-day survival in patients hospitalized with COVID-19.

DESIGN

Retrospective and prospective cohort study.

SETTING

Thirteen acute care hospitals in the New York City area.

PARTICIPANTS

Adult patients hospitalized with a confirmed diagnosis of COVID-19. The development and internal validation cohort included patients hospitalized between March 1 and May 6, 2020. The external validation cohort included patients hospitalized between March 1 and May 5, 2020.

MEASUREMENTS

Demographic, laboratory, clinical, and outcome data were extracted from the electronic health record. Optimal predictors and performance were identified using least absolute shrinkage and selection operator (LASSO) regression with receiver operating characteristic curves and measurements of area under the curve (AUC).

RESULTS

The development and internal validation cohort included 11 095 patients with a median age of 65 years [interquartile range (IQR) 54-77]. Overall 7-day survival was 89%. Serum blood urea nitrogen, age, absolute neutrophil count, red cell distribution width, oxygen saturation, and serum sodium were identified as the 6 optimal of 42 possible predictors of survival. These factors constitute the NOCOS (Northwell COVID-19 Survival) Calculator. Performance in the internal validation, prospective validation, and external validation were marked by AUCs of 0.86, 0.82, and 0.82, respectively.

LIMITATIONS

All participants were hospitalized within the New York City area.

CONCLUSIONS

The NOCOS Calculator uses 6 factors routinely available at hospital admission to predict 7-day survival for patients hospitalized with COVID-19. The calculator is publicly available at https://feinstein.northwell.edu/NOCOS.

Emergency Department disposition decisions and associated mortality and costs in ICU patients with suspected infection

Background

Following emergency department (ED) assessment, patients with infection may be directly admitted to the intensive care unit (ICU) or alternatively admitted to hospital wards or sent home. Those admitted to the hospital wards or sent home may experience future deterioration necessitating ICU admission.

Methods

We used a prospectively collected registry from two hospitals within a single tertiary care hospital network between 2011 and 2014. Patient information, outcomes, and costs were stored in the hospital data warehouse. Patients were categorized into three groups: (1) admitted directly from the ED to the ICU; (2) initially admitted to the hospital wards, with ICU admission within 72 hours of initial presentation; or (3) sent home from the ED, with ICU admission within 72 hours of initial presentation. Using multivariable logistic regression, we sought to compare outcomes and total costs between groups. Total costs were evaluated using a generalized linear model.

Results

A total of 657 patients were included; of these, 338 (51.4%) were admitted directly from the ED to the ICU, 246 (37.4%) were initially admitted to the wards and then to the ICU, and 73 (11.1%) were initially sent home and then admitted to the ICU. In-hospital mortality was lowest among patients admitted directly to the ICU (29.5%), as compared with patients admitted to the ICU from wards (42.7%) or home (61.6%) (P < 0.001). As compared with direct ICU admission, disposition to the ward was associated with an adjusted OR of 1.75 (95% CI, 1.22–2.50; P < 0.01) for mortality, and disposition home was associated with an adjusted OR of 4.02 (95% CI, 2.32–6.98). Mean total costs were lowest among patients directly admitted to the ICU ($26,748), as compared with those admitted from the wards ($107,315) and those initially sent home ($71,492) (P < 0.001). Cost per survivor was lower among patients directly admitted to the ICU ($37,986) than either those initially admitted to the wards ($187,230) or those sent home ($186,390) (P < 0.001).

Conclusions

In comparison with direct admission to the ICU, patients with suspected infection admitted to the ICU who have previously been discharged home or admitted to the ward are associated with higher in-hospital mortality and costs.

Electronic supplementary material

The online version of this article (10.1186/s13054-018-2096-8) contains supplementary material, which is available to authorized users.

Sepsis-3 Septic Shock Criteria and Associated Mortality Among Infected Hospitalized Patients Assessed by a Rapid Response Team

BACKGROUND

Rapid response teams (RRTs) respond to hospitalized patients with deterioration and help determine subsequent management, including ICU admission. In such patients with sepsis and septic shock, the Third International Consensus Definitions for Sepsis and Septic Shock (Sepsis-3) clinical criteria have a potential role in detection, risk stratification, and prognostication; however, their accuracy in comparison with the systemic inflammatory response syndrome (SIRS)-based septic shock criteria is unknown. We sought to evaluate prognostic accuracy of the Sepsis-3 criteria for in-hospital mortality among infected hospitalized patients with acute deterioration.

METHODS

Prospectively collected registry data (2012-2016) from two hospitals, including consecutive hospitalized patients with suspected infection seen by the RRT. We compared the Sepsis-3 criteria with the SIRS-based criteria for prediction of in-hospital mortality.

RESULTS

Of 1,708 included patients, 418 (24.5%) met the Sepsis-3 septic shock criteria, whereas 545 (31.9%) met the SIRS-based septic shock criteria. Patients meeting the Sepsis-3 septic shock criteria had higher in-hospital mortality (40.9% vs 33.5%; P < .0001), ICU admission (99.5% vs 89.2%; P < .001), and discharge rates to long-term care (66.3% vs 53.7%; P < .0001) than patients meeting the SIRS-based septic shock criteria, respectively. Sensitivity and specificity of the quick Sequential (Sepsis-Related) Organ Failure Assessment were 64.9% and 92.2% for prediction of in-hospital mortality, whereas SIRS criteria had a sensitivity and specificity of 91.6% and 23.6%, respectively.

CONCLUSIONS

Hospitalized patients with deterioration from suspected infection had higher risk of in-hospital mortality if they met the Sepsis-3 septic shock criteria than the SIRS-based septic shock criteria. Therefore, use of the Sepsis-3 criteria may be preferable in the prognostication and disposition of these patients who are critically ill.

Effect of a Single Dose of Oral Opioid and Nonopioid Analgesics on Acute Extremity Pain in the Emergency Department: A Randomized Clinical Trial

IMPORTANCE

The choice of analgesic to treat acute pain in the emergency department (ED) lacks a clear evidence base. The combination of ibuprofen and acetaminophen (paracetamol) may represent a viable nonopioid alternative.

OBJECTIVES

To compare the efficacy of 4 oral analgesics.

DESIGN, SETTINGS, AND PARTICIPANTS

Randomized clinical trial conducted at 2 urban EDs in the Bronx, New York, that included 416 patients aged 21 to 64 years with moderate to severe acute extremity pain enrolled from July 2015 to August 2016.

INTERVENTIONS

Participants (104 per each combination analgesic group) received 400 mg of ibuprofen and 1000 mg of acetaminophen; 5 mg of oxycodone and 325 mg of acetaminophen; 5 mg of hydrocodone and 300 mg of acetaminophen; or 30 mg of codeine and 300 mg of acetaminophen.

MAIN OUTCOMES AND MEASURES

The primary outcome was the between-group difference in decline in pain 2 hours after ingestion. Pain intensity was assessed using an 11-point numerical rating scale (NRS), in which 0 indicates no pain and 10 indicates the worst possible pain. The predefined minimum clinically important difference was 1.3 on the NRS. Analysis of variance was used to test the overall between-group difference at P = .05 and 99.2% CIs adjusted for multiple pairwise comparisons.

RESULTS

Of 416 patients randomized, 411 were analyzed (mean [SD] age, 37 [12] years; 199 [48%] women; 247 [60%] Latino). The baseline mean NRS pain score was 8.7 (SD, 1.3). At 2 hours, the mean NRS pain score decreased by 4.3 (95% CI, 3.6 to 4.9) in the ibuprofen and acetaminophen group; by 4.4 (95% CI, 3.7 to 5.0) in the oxycodone and acetaminophen group; by 3.5 (95% CI, 2.9 to 4.2) in the hydrocodone and acetaminophen group; and by 3.9 (95% CI, 3.2 to 4.5) in the codeine and acetaminophen group (P = .053). The largest difference in decline in the NRS pain score from baseline to 2 hours was between the oxycodone and acetaminophen group and the hydrocodone and acetaminophen group (0.9; 99.2% CI, -0.1 to 1.8), which was less than the minimum clinically important difference in NRS pain score of 1.3. Adverse events were not assessed.

CONCLUSIONS AND RELEVANCE

For patients presenting to the ED with acute extremity pain, there were no statistically significant or clinically important differences in pain reduction at 2 hours among single-dose treatment with ibuprofen and acetaminophen or with 3 different opioid and acetaminophen combination analgesics. Further research to assess adverse events and other dosing may be warranted.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT02455518.

Use of the low-frequency/high-frequency ratio of heart rate variability to predict short-term deterioration in emergency department patients with sepsis

OBJECTIVE

To examine the ability of the low-frequency/high-frequency (LF/HF) ratio of heart rate variability (HRV) analysis to identify patients with sepsis at risk of early deterioration.

METHODS

This is a prospective observational cohort study of patients with sepsis presenting to the Montefiore Medical Center ED from December 2014 through September 2015. On presentation, a single ECG Holter recording was obtained and analysed to obtain the LF/HF ratio of HRV. Initial Sequential Organ Failure Assessment (SOFA) scores were computed. Patients were followed for 72 hours to identify those with early deterioration.

RESULTS

466 patients presenting to the ED with sepsis were analysed. Thirty-two (7%) reached at least one endpoint within 72 hours. An LF/HF ratio <1 had a sensitivity and specificity of 34% (95% CI (19% to 53%)) and 82% (95% CI (78% to 85%)), respectively, with positive and negative likelihood ratios of 1.9 (95% CI (1.1 to 3.2)) and 0.8 (95% CI (0.6 to 1.0)). An initial SOFA score ≥3 had a sensitivity and specificity of 38% (95% CI (22% to 56%)) and 92% (95% CI (89% to 95%)), with positive and negative likelihood ratios of 4.9 (95% CI (2.8 to 8.6)) and 0.7 (95% CI (0.5 to 0.9)). The composite measure of HRV+SOFA had improved sensitivity (56%, 95% CI (38% to 73%)) but at the expense of specificity (77%, 95% CI (72% to 80%)), with positive and negative likelihood ratios of 2.4 (95% CI (1.7 to 3.4)) and 0.6 (95% CI (0.4 to 0.9)). Receiver operating characteristic analysis did not identify a superior alternate threshold for the LF/HF ratio. Kaplan-Meier survival functions differed significantly (p=0.02) between low (<1) and high (≥1) LF/HF groups.

CONCLUSIONS

While we found a statistically significant relationship between HRV, SOFA and HRV+SOFA, and early deterioration, none reliably functioned as a clinical predictive tool. More complex multivariable models will likely be required to construct models with clinical utility.

Galantamine alleviates inflammation and insulin resistance in patients with metabolic syndrome in a randomized trial

BACKGROUND

Metabolic syndrome (MetS) is an obesity-driven condition of pandemic proportions that increases the risk of type 2 diabetes and cardiovascular disease. Pathophysiological mechanisms are poorly understood, though inflammation has been implicated in MetS pathogenesis. The aim of this study was to assess the effects of galantamine, a centrally acting acetylcholinesterase inhibitor with antiinflammatory properties, on markers of inflammation implicated in insulin resistance and cardiovascular risk, and other metabolic and cardiovascular indices in subjects with MetS.

METHODS

In this randomized, double-blind, placebo-controlled trial, subjects with MetS (30 per group) received oral galantamine 8 mg daily for 4 weeks, followed by 16 mg daily for 8 weeks or placebo. The primary outcome was inflammation assessed through plasma levels of cytokines and adipokines associated with MetS. Secondary endpoints included body weight, fat tissue depots, plasma glucose, insulin, homeostasis model assessment of insulin resistance (HOMA-IR), cholesterol (total, HDL, LDL), triglycerides, BP, heart rate, and heart rate variability (HRV).

RESULTS

Galantamine resulted in lower plasma levels of proinflammatory molecules TNF (-2.57 pg/ml [95% CI -4.96 to -0.19]; P = 0.035) and leptin (-12.02 ng/ml [95% CI -17.71 to -6.33]; P < 0.0001), and higher levels of the antiinflammatory molecules adiponectin (2.71 μg/ml [95% CI 1.93 to 3.49]; P < 0.0001) and IL-10 (1.32 pg/ml, [95% CI 0.29 to 2.38]; P = 0.002) as compared with placebo. Galantamine also significantly lowered plasma insulin and HOMA-IR values, and altered HRV.

CONCLUSION

Low-dose galantamine alleviates inflammation and insulin resistance in MetS subjects. These findings support further study of galantamine in MetS therapy.

TRIAL REGISTRATION

ClinicalTrials.gov, number NCT02283242.

FUNDING

Fundação de Amparo a Pesquisa do Estado de São Paulo (FAPESP) and Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), Brazil, and the NIH.

Generalizability and Effectiveness of Butterfly Phlebotomy in Reducing Hemolysis

OBJECTIVES

The objective was to test the hypothesis that exclusive use of butterfly needles for phlebotomy, compared with sample collection via intravenous (IV) catheter, will reduce rates of sample hemolysis.

METHODS

This was an observational study of hemolysis rates before and after implementation of a "butterfly-only" phlebotomy protocol. Weekly hemolysis rates, generated by the central laboratory, were collected and the proportion of hemolyzed specimens before and after protocol implementation were compared.

RESULTS

Prior to institution of the butterfly-only protocol, 11.3% of specimens sent from the emergency department were reported as hemolyzed. During the postintervention period, only 4.3% of specimens were hemolyzed for a proportionate decrease of 62% and an absolute decrease of 7.0% (95% confidence interval = 6.6% to 7.3%).

CONCLUSIONS

Use of a butterfly-only phlebotomy protocol cuts hemolysis rates by more than half when compared with IV catheter phlebotomy.

A study of the workforce in emergency medicine: 1999

STUDY OBJECTIVE

We estimate the total number of physicians practicing clinical emergency medicine during a specified period, describe certain characteristics of those individuals to estimate the total number of full-time equivalents (FTEs) and the total number of individuals needed to staff those FTEs, and compare the data collected with those data collected in 1997.

METHODS

Data were gathered from a survey of a random sample of 2,153 hospitals drawn from a population of 5,329 hospitals reported by the American Hospital Association as having, or potentially having, an emergency department. The survey instrument addressed items such as descriptive data on the institution, enumeration of physicians in the ED, and the total number of physicians working during the period from June 6 to June 9, 1999. Demographic data on the individuals were also collected.

RESULTS

A total of 940 hospitals responded (a 44% return rate). These hospitals reported that a total of 6,719 physicians were working during the specified period, or an average of 7.85 persons scheduled per institution. The physicians were scheduled for a total of 347,702 hours. The average standard for FTE was 40 clinical hours per week. This equates to 4,346 FTEs or 5.29 FTEs per institution. The ratio of persons to FTEs was 1.48:1. With regard to demographics, 83% of the physicians were men, and 82% were white. Their average age was 42.6 years. As for professional credentials, 42% were emergency medicine residency trained, and 58% were board certified in emergency medicine; 50% were certified by the American Board of Emergency Medicine.

CONCLUSION

Given that there are 5,064 hospitals with EDs and given that the data indicate that there are 5.35 FTEs per ED, the total number of FTEs is projected to be 27,067 (SE=500). Given further that the data indicate a physician/FTE ratio of 1.47:1, we conclude that there are 39,746 persons (SE=806) needed to staff those FTEs. When adjusted for persons working at more than one ED, that number is reduced to 31,797. When the 1999 data are compared with those collected in 1997, we note a statistically significant decline in the number of hospital EDs, from 5,126 in 1997 to 5,064 in 1999 (P =.02). The total number of emergency physicians remained the same over the 2-year period, whereas the number of FTEs per institution increased from 5.11 to 5.35. The physician/FTE ratio remained unchanged.

Evidence of methodologic bias in the derivation of the Science Citation Index impact factor

STUDY OBJECTIVE

The "impact factor" published in Science Citation Index (SCI) is widely used in the scientific community to measure the relative importance of a medical journal. In contrast to all other indicators of academic growth in emergency medicine, impact factors for emergency medicine journals have remained low and unchanged since the inception of the specialty. We wished to investigate this incongruity.

METHODS

We examined the methodology used to derive the SCI's journal impact factor.

RESULTS

The impact factor for journals is defined mathematically as the number of times a journal is cited over a period of time (the numerator) divided by the number of articles published by that journal during the same period (the denominator). Citation counts are derived from examination of all references contained in a subset of journals known as "source" journals. No emergency medicine journals are included in this group. The only source of citations for emergency medicine journals is from journals outside of emergency medicine. This produces small numerators with relatively constant denominators, leading to low impact factors.

CONCLUSION

The apparent failure of emergency medicine journals, as measured by the SCI impact factor, to keep pace with other indicators of academic development of the field is at least in part attributable to a methodologic bias inherent in the derivation of this factor.

Alternative to the Science Citation Index impact factor as an assessment of emergency medicine's scientific contributions

STUDY OBJECTIVE

The Science Citation Index "impact factor" is the only available quantitative estimate of a journal's scientific contributions. However, the derivation of this factor contains an intrinsic bias that underestimates the impact of emergency medicine journals. We wished to test the hypothesis that use of an alternative criterion standard would provide an improved profile of the scientific contributions of emergency medicine journals relative to those of other specialties.

METHODS

We used an observational, longitudinal, comparative design in which all Index Medicus citations from Advanced Cardiac Life Support (ACLS) publications were aggregated by journal and then stratified by specialty. Proportions and proportionate trends, relative to total citations, were reported by specialty, facilitating comparison of emergency medicine with other disciplines.

RESULTS

Among all eight ACLS publications (1974-1994) 4,062 citations met the inclusion criteria. Emergency medicine journals were referenced in 16% of eligible citations (99% confidence interval [CI], 14% to 17%), a figure exceeded only by internal medicine and cardiology journals. Emergency medicine was the only discipline to show a significant proportionate increase in contributions over the 20-year study period (P < .001 by chi 2 for linear trend analysis).

CONCLUSION

Contrary to the implications of a low impact factor, an analysis of journal citations in ACLS publications over two decades suggests that emergency medicine has made significant contributions to a broad and important area of scientific inquiry.

Isolated intrathoracic injury with air bag use

The restrained (air bag and seatbelt) driver of a vehicle involved in a high-speed motor-vehicle accident sustained a tear of the thoracic aorta with no signs of external injury. Air bag deployment may mask significant internal injury, and a high index of suspicion is warranted in such situations.