Improving surface PM2.5 forecasts in the United States using an ensemble of chemical transport model outputs: 2. bias correction with satellite data for rural areas

This work serves as the second of a two-part study to improve surface PM2.5 forecasts in the continental U.S. through the integrated use of multi-satellite aerosol optical depth (AOD) products (MODIS Terra/Aqua and VIIRS DT/DB), multi chemical transport model (CTM) (GEOS-Chem, WRF-Chem and CMAQ) outputs and ground observations. In part I of the study, a multi-model ensemble Kalman filter (KF) technique using three CTM outputs and ground observations was developed to correct forecast bias and generate a single best forecast of PM2.5 for next day over non-rural areas that have surface PM2.5 measurements in the proximity of 125 km. Here, with AOD data, we extended the bias correction into rural areas where the closest air quality monitoring station is at least 125 - 300 km away. First, we ensembled all of satellite AOD products to yield the single best AOD. Second, we corrected daily PM2.5 in rural areas from multiple models through the AOD spatial pattern between these areas and non-rural areas, referred to as "extended ground truth" or EGT, for today. Lastly, we applied the KF technique to update the bias in the forecast for next day using the EGT. Our results find that the ensemble of bias-corrected daily PM2.5 from three models for both today and next day show the best performance. Together, the two-part study develops a multi-model and multi-AOD bias correction technique that has the potential to improve PM2.5 forecasts in both rural and non-rural areas in near real time, and be readily implemented at state levels.

Monthly Global Estimates of Fine Particulate Matter and Their Uncertainty

Annual global satellite-based estimates of fine particulate matter (PM2.5) are widely relied upon for air-quality assessment. Here, we develop and apply a methodology for monthly estimates and uncertainties during the period 1998-2019, which combines satellite retrievals of aerosol optical depth, chemical transport modeling, and ground-based measurements to allow for the characterization of seasonal and episodic exposure, as well as aid air-quality management. Many densely populated regions have their highest PM2.5 concentrations in winter, exceeding summertime concentrations by factors of 1.5-3.0 over Eastern Europe, Western Europe, South Asia, and East Asia. In South Asia, in January, regional population-weighted monthly mean PM2.5 concentrations exceed 90 μg/m3, with local concentrations of approximately 200 μg/m3 for parts of the Indo-Gangetic Plain. In East Asia, monthly mean PM2.5 concentrations have decreased over the period 2010-2019 by 1.6-2.6 μg/m3/year, with decreases beginning 2-3 years earlier in summer than in winter. We find evidence that global-monitored locations tend to be in cleaner regions than global mean PM2.5 exposure, with large measurement gaps in the Global South. Uncertainty estimates exhibit regional consistency with observed differences between ground-based and satellite-derived PM2.5. The evaluation of uncertainty for agglomerated values indicates that hybrid PM2.5 estimates provide precise regional-scale representation, with residual uncertainty inversely proportional to the sample size.

Effects of COVID-19 lockdowns on fine particulate matter concentrations

Lockdowns during the COVID-19 pandemic provide an unprecedented opportunity to examine the effects of human activity on air quality. The effects on fine particulate matter (PM2.5) are of particular interest, as PM2.5 is the leading environmental risk factor for mortality globally. We map global PM2.5 concentrations for January to April 2020 with a focus on China, Europe, and North America using a combination of satellite data, simulation, and ground-based observations. We examine PM2.5 concentrations during lockdown periods in 2020 compared to the same periods in 2018 to 2019. We find changes in population-weighted mean PM2.5 concentrations during the lockdowns of -11 to -15 μg/m3 across China, +1 to -2 μg/m3 across Europe, and 0 to -2 μg/m3 across North America. We explain these changes through a combination of meteorology and emission reductions, mostly due to transportation. This work demonstrates regional differences in the sensitivity of PM2.5 to emission sources.

Global Estimates and Long-Term Trends of Fine Particulate Matter Concentrations (1998-2018)

Exposure to outdoor fine particulate matter (PM_2.5) is a leading risk factor for mortality. We develop global estimates of annual PM_2.5 concentrations and trends for 1998-2018 using advances in satellite observations, chemical transport modeling, and ground-based monitoring. Aerosol optical depths (AODs) from advanced satellite products including finer resolution, increased global coverage, and improved long-term stability are combined and related to surface PM_2.5 concentrations using geophysical relationships between surface PM_2.5 and AOD simulated by the GEOS-Chem chemical transport model with updated algorithms. The resultant annual mean geophysical PM_2.5 estimates are highly consistent with globally distributed ground monitors (R² = 0.81; slope = 0.90). Geographically weighted regression is applied to the geophysical PM_2.5 estimates to predict and account for the residual bias with PM_2.5 monitors, yielding even higher cross validated agreement (R² = 0.90-0.92; slope = 0.90-0.97) with ground monitors and improved agreement compared to all earlier global estimates. The consistent long-term satellite AOD and simulation enable trend assessment over a 21 year period, identifying significant trends for eastern North America (-0.28 ± 0.03 μg/m³/yr), Europe (-0.15 ± 0.03 μg/m³/yr), India (1.13 ± 0.15 μg/m³/yr), and globally (0.04 ± 0.02 μg/m³/yr). The positive trend (2.44 ± 0.44 μg/m³/yr) for India over 2005-2013 and the negative trend (-3.37 ± 0.38 μg/m³/yr) for China over 2011-2018 are remarkable, with implications for the health of billions of people.

Interannual variability and trends of combustion aerosol and dust in major continental outflows revealed by MODIS retrievals and CAM5 simulations during 2003-2017

Emissions and long-range transport of mineral dust and combustion-related aerosol from burning fossil fuels and biomass vary from year to year, driven by the evolution of the economy and changes in meteorological conditions and environmental regulations. This study offers both satellite and model perspectives on the interannual variability and possible trends of combustion aerosol and dust in major continental outflow regions over the past 15 years (2003-2017). The decade-long record of aerosol optical depth (AOD, denoted as τ), separately for combustion aerosol (τ _c) and dust (τ _d), over global oceans is derived from the Collection 6 aerosol products of the Moderate Resolution Imaging Spectroradiometer (MODIS) onboard both Terra and Aqua. These MODIS Aqua datasets, complemented by aerosol source-tagged simulations using the Community Atmospheric Model version 5 (CAM5), are then analyzed to understand the interannual variability and potential trends of τ _c and τ _d in the major continental outflows. Both MODIS and CAM5 consistently yield a similar decreasing trend of -0.017 to -0.020 per decade for τ _c over the North Atlantic Ocean and the Mediterranean Sea that is attributable to reduced emissions from North America and Europe, respectively. On the contrary, both MODIS and CAM5 display an increasing trend of +0.017 to +0.036 per decade for τ _c over the tropical Indian Ocean, the Bay of Bengal, and the Arabian Sea, which reflects the influence of increased anthropogenic emissions from South Asia and the Middle East in the last 2 decades. Over the northwestern Pacific Ocean, which is often affected by East Asian emissions of pollution and dust, the MODIS retrievals show a decreasing trend of -0.021 per decade for τ _c and -0.012 per decade for τ _d, which is, however, not reproduced by the CAM5 model. In other outflow regions strongly influenced by biomass burning smoke or dust, both MODIS retrievals and CAM5 simulations show no statistically significant trends; the MODIS-observed interannual variability is usually larger than that of the CAM5 simulation.

Exploring aerosols near clouds with high-spatial-resolution aircraft remote sensing during SEAC4RS

Since aerosols are important to our climate system, we seek to observe the variability of aerosol properties within cloud systems. When applied to the satellite-borne Moderate-resolution Imaging Spectroradiometer (MODIS), the Dark Target (DT) retrieval algorithm provides global aerosol optical depth (AOD at 0.55 μm) in cloud-free scenes. Since MODIS' resolution (500 m pixels, 3 km or 10 km product) is too coarse for studying near-cloud aerosol, we ported the DT algorithm to the high-resolution (~50 m pixels) enhanced-MODIS Airborne Simulator (eMAS), which flew on the high-altitude ER-2 during the Studies of Emissions, Atmospheric Composition, Clouds and Climate Coupling by Regional Surveys (SEAC4RS) Airborne Science Campaign over the U.S. in 2013. We find that even with aggressive cloud screening, the ~0.5 km eMAS retrievals show enhanced AOD, especially within 6 km of a detected cloud. To determine the cause of the enhanced AOD, we analyze additional eMAS products (cloud retrievals and degraded-resolution AOD), co-registered Cloud Physics Lidar (CPL) profiles, MODIS aerosol retrievals, and ground-based Aerosol Robotic Network (AERONET) observations. We also define spatial metrics to indicate local cloud distributions near each retrieval, and then separate into near-cloud and far-from-cloud environments. The comparisons show that low cloud masking is robust, and unscreened thin cirrus would have only a small impact on retrieved AOD. Some of the enhancement is consistent with clear-cloud transition zone microphysics such as aerosol swelling. However, 3D radiation interaction between clouds and the surrounding clear air appears to be the primary cause of the high AOD near clouds.

Exploring systematic offsets between aerosol products from the two MODIS sensors

Long-term measurements of global aerosol loading and optical properties are essential for assessing climate-related questions. Using observations of spectral reflectance and radiance, the dark-target (DT) aerosol retrieval algorithm is applied to Moderate-resolution Imaging Spectroradiometer sensors on both Terra (MODIS-T) and Aqua (MODIS-A) satellites, deriving products (known as MOD04 and MYD04, respectively) of global aerosol optical depth (AOD at 0.55 μm) over both land and ocean, and Angstrom Exponent (AE derived from 0.55 and 0.86 μm) over ocean. Here, we analyse the overlapping time series (since mid-2002) of the Collection 6 (C6) aerosol products. Global monthly mean AOD from MOD04 (Terra with morning overpass) is consistently higher than MYD04 (Aqua with afternoon overpass) by ~13% (~0.02 over land and ~0.015 over ocean), and this offset (MOD04 - MYD04), has seasonal as well as long-term variability. Focusing on 2008, and deriving yearly gridded mean AOD and AE, we find that over ocean, the MOD04 (morning) AOD is higher and the AE is lower. Over land, there is more variability, but only biomass-burning regions tend to have AOD lower for MOD04. Using simulated aerosol fields from the Goddard Earth Observing System (GEOS-5) Earth system model, and sampling separately (in time and space) along each MODIS-observed swath during 2008, the magnitudes of morning versus afternoon offsets of AOD and AE are smaller than those in the C6 products. Since the differences are not easily attributed to either aerosol diurnal cycles or sampling issues, we test additional corrections to the input reflectance data. The first, known as C6+, corrects for long-term changes to each sensors' polarization sensitivity, response-versus-scan angle, and to cross-calibration from MODIS-T to MODIS-A. A second convolves the de-trending and cross-calibration into scaling factors. Each method was applied upstream of the aerosol retrieval, using 2008 data. While both methods reduced the overall AOD offset over land from 0.02 to 0.01, neither significantly reduced the AOD offset over ocean. The overall negative AE offset was reduced. A Collection (C6.1) of all MODIS-atmosphere products was released, but we expect that the C6.1 aerosol products will maintain similar overall AOD and AE offsets. We conclude that: a) users should not interpret global differences between Terra and Aqua aerosol products as representing a true diurnal signal in the aerosol. b) Because the MODIS-A product appears to have overall smaller bias compared to ground-truth, it may be more suitable for some applications, however c) since the AOD offset is only ~0.02 and within noise level for single retrievals, both MODIS products may be adequate for most applications.

Observations of the Interaction and Transport of Fine Mode Aerosols with Cloud and/or Fog in Northeast Asia from Aerosol Robotic Network (AERONET) and Satellite Remote Sensing

Analysis of sun photometer measured and satellite retrieved aerosol optical depth (AOD) data has shown that major aerosol pollution events with very high fine mode AOD (>1.0 in mid-visible) in the China/Korea/Japan region are often observed to be associated with significant cloud cover. This makes remote sensing of these events difficult even for high temporal resolution sun photometer measurements. Possible physical mechanisms for these events that have high AOD include a combination of aerosol humidification, cloud processing, and meteorological co-variation with atmospheric stability and convergence. The new development of Aerosol Robotic network (AERONET) Version 3 Level 2 AOD with improved cloud screening algorithms now allow for unprecedented ability to monitor these extreme fine mode pollution events. Further, the Spectral Deconvolution Algorithm (SDA) applied to Level 1 data (L1; no cloud screening) provides an even more comprehensive assessment of fine mode AOD than L2 in current and previous data versions. Studying the 2012 winter-summer period, comparisons of AERONET L1 SDA daily average fine mode AOD data showed that Moderate Resolution Imaging Spectroradiometer (MODIS) satellite remote sensing of AOD often did not retrieve and/or identify some of the highest fine mode AOD events in this region. Also, compared to models that include data assimilation of satellite retrieved AOD, the L1 SDA fine mode AOD was significantly higher in magnitude, particularly for the highest AOD events that were often associated with significant cloudiness.

Developing and diagnosing climate change indicators of regional aerosol optical properties

Given the importance of aerosol particles to radiative transfer via aerosol-radiation interactions, a methodology for tracking and diagnosing causes of temporal changes in regional-scale aerosol populations is illustrated. The aerosol optical properties tracked include estimates of total columnar burden (aerosol optical depth, AOD), dominant size mode (Ångström exponent, AE), and relative magnitude of radiation scattering versus absorption (single scattering albedo, SSA), along with metrics of the structure of the spatial field of these properties. Over well-defined regions of North America, there are generally negative temporal trends in mean and extreme AOD, and SSA. These are consistent with lower aerosol burdens and transition towards a relatively absorbing aerosol, driven primarily by declining sulfur dioxide emissions. Conversely, more remote regions are characterized by increasing mean and extreme AOD that is attributed to increased local wildfire emissions and long-range (transcontinental) transport. Regional and national reductions in anthropogenic emissions of aerosol precursors are leading to declining spatial autocorrelation in the aerosol fields and increased importance of local anthropogenic emissions in dictating aerosol burdens. However, synoptic types associated with high aerosol burdens are intensifying (becoming more warm and humid), and thus changes in synoptic meteorology may be offsetting aerosol burden reductions associated with emissions legislation.

Retrieval of aerosol optical properties using MERIS observations: Algorithm and some first results

The MEdium Resolution Imaging Spectrometer (MERIS) instrument on board ESA Envisat made measurements from 2002 to 2012. Although MERIS was limited in spectral coverage, accurate Aerosol Optical Thickness (AOT) from MERIS data are retrieved by using appropriate additional information. We introduce a new AOT retrieval algorithm for MERIS over land surfaces, referred to as eXtensible Bremen AErosol Retrieval (XBAER). XBAER is similar to the "dark-target" (DT) retrieval algorithm used for Moderate-resolution Imaging Spectroradiometer (MODIS), in that it uses a lookup table (LUT) to match to satellite-observed reflectance and derive the AOT. Instead of a global parameterization of surface spectral reflectance, XBAER uses a set of spectral coefficients to prescribe surface properties. In this manner, XBAER is not limited to dark surfaces (vegetation) and retrieves AOT over bright surface (desert, semiarid, and urban areas). Preliminary validation of the MERIS-derived AOT and the ground-based Aerosol Robotic Network (AERONET) measurements yield good agreement, the resulting regression equation is y = (0.92 × ± 0.07) + (0.05 ± 0.01) and Pearson correlation coefficient of R = 0.78. Global monthly means of AOT have been compared from XBAER, MODIS and other satellite-derived datasets.

Global Estimates of Fine Particulate Matter using a Combined Geophysical-Statistical Method with Information from Satellites, Models, and Monitors

We estimated global fine particulate matter (PM2.5) concentrations using information from satellite-, simulation- and monitor-based sources by applying a Geographically Weighted Regression (GWR) to global geophysically based satellite-derived PM2.5 estimates. Aerosol optical depth from multiple satellite products (MISR, MODIS Dark Target, MODIS and SeaWiFS Deep Blue, and MODIS MAIAC) was combined with simulation (GEOS-Chem) based upon their relative uncertainties as determined using ground-based sun photometer (AERONET) observations for 1998-2014. The GWR predictors included simulated aerosol composition and land use information. The resultant PM2.5 estimates were highly consistent (R(2) = 0.81) with out-of-sample cross-validated PM2.5 concentrations from monitors. The global population-weighted annual average PM2.5 concentrations were 3-fold higher than the 10 μg/m(3) WHO guideline, driven by exposures in Asian and African regions. Estimates in regions with high contributions from mineral dust were associated with higher uncertainty, resulting from both sparse ground-based monitoring, and challenging conditions for retrieval and simulation. This approach demonstrates that the addition of even sparse ground-based measurements to more globally continuous PM2.5 data sources can yield valuable improvements to PM2.5 characterization on a global scale.

A rapid diagnostic and treatment center for patients with chest pain in the emergency department

STUDY OBJECTIVE

To evaluate a comprehensive diagnostic 9-hour evaluation (Heart ER Program) for patients with possible acute ischemic coronary syndromes.

DESIGN

Retrospective review of consecutive patients.

SETTING

Urban tertiary care emergency department.

PARTICIPANTS

A total of 1,010 patients with symptoms suggestive of acute ischemic coronary syndrome was enrolled in the Heart ER Program over the first 32 months of operation. Patients with history of coronary artery disease, hemodynamic instability, acute ST-segment elevation or depression of more than 1 mm, or a clinical syndrome consistent with unstable angina were directly admitted to the hospital.

INTERVENTION

Patients underwent serial testing for creatine kinase (CK-MB) on presentation to the Heart ER and 3, 6, and 9 hours later with continuous 12-lead ECGs/serial ST-segment trend monitoring for 9 hours. Two-dimensional echocardiography and graded exercise testing were performed in the ED after the 9-hour evaluation period.

RESULTS

Of 1,010 patients, 829 (82.1%) were released home from the ED; 153 (15.1%) required admission for further cardiac evaluation. Fifty-two of 153 (33.9%) admitted patients were found to have a cardiac cause for their symptoms; 43 had acute ischemic coronary syndromes (12, acute myocardial infarction; 31, angina or unstable angina).

CONCLUSION

The Heart ER program provides an effective method for evaluating low- to moderate-risk patients with possible acute ischemic coronary syndrome in the ED setting.

Role of emergency medicine residency programs in determining emergency medicine career choice among medical students

STUDY OBJECTIVE

To characterize the role of emergency medicine residency programs in determining emergency medicine career choice among medical students.

DESIGN

Observational, cross-sectional, descriptive study. Information on student career choice was obtained through a targeted query of the National Resident Matching Program data base, simultaneously stratified by specialty and school, and adjusted for class size.

PARTICIPANTS

All accredited emergency medicine residency programs and four-year allopathic medical schools.

RESULTS

Fifty-two schools (42%) had a closely affiliated emergency medicine residency program, ie, one based primarily at the institution's main teaching hospital(s). This configuration was associated with a 70% increase in the median proportion of students choosing emergency medicine as a career when compared to the 73 schools with no closely affiliated emergency medicine residency (5.1% vs 3.0%, P < .0001). When institutions were stratified by overall commitment to emergency medicine, the median proportion of students choosing emergency medicine as a career was 2.9% for institutions with a minimal commitment to emergency medicine (neither an academic department of emergency medicine nor a closely affiliated emergency medicine residency), 4.1% for institutions with a moderate commitment to emergency medicine (either a department of emergency medicine or an emergency medicine residency, but not both), and 5.7% for institutions with a substantial commitment to emergency medicine (a department of emergency medicine and an emergency medicine residency) (P < .0001). When institutional commitment to emergency medicine was examined in a simple multivariate model, only the presence of an emergency medicine residency was associated independently with student career choice (P < .001).

CONCLUSION

An emergency medicine residency program that is closely affiliated with a medical school is strongly and independently associated with a quantitatively and statistically significant increase in the proportion of students from that school who choose a career in emergency medicine. These data support the proposition that, if emergency medicine is to meet national manpower shortage needs by attracting students to the specialty, it must establish residency programs within the primary teaching hospital(s) of medical schools. Such a configuration does not currently exist in the majority of schools.

Emergency-department diagnosis of acute myocardial infarction and ischemia: a cost analysis of two diagnostic protocols

OBJECTIVE

To assess the potential cost savings of the emergency-department (ED) diagnosis of acute myocardial infarction (AMI) and other myocardial ischemia using a nine- hour ED evaluation protocol.

METHODS

This one-year study of chest-pain evaluation unit (CPEU) patient charges was undertaken at two midwestern urban university hospital EDs. Included in the study were 447 patients presenting to the EDs with chest pain consistent with myocardial ischemia, nondiagnostic electrocardiograms (ECGs), and stable vital signs. Following initial ED evaluation, CPEU patients underwent nine hours of continuous ECG ST-segment monitoring with serum CK-MB levels determined at zero, three, six, and nine hours. Nonrandomized concurrent chest pain patients with routine ED evaluation and hospital admission without CPEU workup served as controls. At Center 1, patients with negative CPEU evaluations underwent immediate echocardiography (echo) and graded exercise testing (GXT) followed by ED release (CPEU;REL). At Center 2, CPEU patients were released from the ED for outpatient stress thallium testing (CPEU;REL). At Center 2, CPEU patients with positive workups as indicated by elevated CK-MB levels, ischemia by ST-segment monitoring, or positive echo/GXT/ stress thallium testing were admitted to the hospital for further testing. Control patients were admitted directly to the hospital to evaluate for AMI. Hospital charges for CPEU and control groups were compared.

RESULTS

(Total charges in dollars, mean +/- SD, student's t-test): [table: see text]

CONCLUSION

At both centers, hospital charges related to the acute evaluation of chest pain were significantly lower with this ED diagnostic protocol for AMI and myocardial ischemia.

Current status of academic emergency medicine within academic medicine in the United States

OBJECTIVE

To characterize the status of emergency medicine within U.S. academic medical centers.

METHODS

All accredited emergency medicine residency programs and all four-year allopathic medical schools in the United States were identified. Institutions were defined as academic medical centers based upon NIH research grant funding. These institutions were ranked using five measures of academic stature: a survey of medical school deans, a survey of internal medicine residency directors, level of research funding, characteristics of the student body, and an unweighted composite variable reflecting overall academic stature. The relationship between institutional academic stature and an empiric scale of institutional affiliation with emergency medicine was assessed.

RESULTS

Sixty-two institutions were designated academic medical centers. These medical schools captured 90% of all NIH grant monies awarded in fiscal year 1990. Twenty-six of 87 emergency medicine residency programs (30%) were closely affiliated with one of these medical schools. Within academic medical centers, the presence of a residency or an academic department of emergency medicine was inversely associated with the medical school deans' ranking (p < 0.005), research rank (p < 0.001), and composite academic rank (p < 0.001).

CONCLUSION

The majority of emergency medicine residency programs (70%) are not closely affiliated with institutions receiving the bulk (90%) of NIH resources for research. Within the institutions receiving the majority of NIH funding, there is a quantitatively and statistically significant inverse association of institutional emergency medicine affiliation and institutional academic rank.

Factors associated with career longevity in residency-trained emergency physicians

STUDY OBJECTIVE

To test the hypothesis that residency-trained emergency physicians who left the practice of emergency medicine do not differ significantly from those who continue to practice.

DESIGN

A retrospective cohort study using a mailed questionnaire.

TYPE OF PARTICIPANTS

Eight hundred fifty-eight emergency medicine residency graduates from 1978 through 1982.

METHODS

A mailed questionnaire was used to obtain data from the study population. Individuals who did not respond to the first mailing were sent a second survey six weeks later. A sample of 10% of nonrespondents was contacted by telephone and compared with respondents on five variables. Respondents were divided into physicians who continued to practice emergency medicine and those who had elected to leave the specialty. The variables used to compare the two groups included personal and professional demographics, career satisfaction, and satisfaction with training. chi 2, Fisher's exact t-test, and logistic regression were used to analyze the data with an a priori level of significance set at .05.

MEASUREMENTS AND MAIN RESULTS

There were 539 complete responses for a response rate of 62.8%. No statistical differences between responders and nonresponders were identified. The ten-year survival rate of respondents was 84.9%. Those who left emergency medicine were less likely to be board certified in emergency medicine (P less than .001), were more likely to be board certified in another field (P = .001), were less likely to work with residents during their emergency medicine practice (P = .009), and were more likely to report an annual gross income of less than $100,000 per year (P less than .001). Emergency physicians who have left the field were less likely to report being satisfied or very satisfied with their initial choice of emergency medicine as a specialty (P = .001). There was no difference in satisfaction with the quality of emergency medicine residency training (P = .183).

CONCLUSION

Career longevity of residency-trained emergency physicians has been greater than early predictions. Interactions with residents, higher income, satisfaction with training decision, and board certification in emergency medicine are variables associated with a higher retention rate.

Descriptive analysis of residency-trained emergency medicine physicians

The purpose of this study was to analyze the demographics, practice characteristics, and job satisfaction of physicians who completed emergency medicine residencies. A questionnaire was mailed to 858 physicians who graduated from residencies between 1978 and 1982. A 62.8% response rate (n = 539) was achieved. The majority of respondents were satisfied or very satisfied with their choice of a career in emergency medicine and with the quality of their residency training. Over 22% of respondents cited lack of preparation to perform administrative tasks as a significant weakness of their residency training. The results of survey indicate that emergency medicine physicians are engaged primarily in clinical practice, but that administrative duties increase rapidly in the years following residency graduation. Emergency medicine physicians are still highly concentrated in states in which emergency medicine residencies are located. The percentage of graduates choosing academic careers is smaller than reported in studies of earlier graduates.

Single-dose ceftriaxone treatment of urinary tract infections

Single-dose antibiotic therapy for urinary tract infections in which no underlying structural or neurologic lesions are present holds the promise of greater patient compliance and convenience. We present the results of a study comparing a single intramuscular dose of a long-acting, third-generation cephalosporin, ceftriaxone, with a standard, five-day regimen of trimethoprim-sulfamethoxazole (TMS). Fifty-two patients were entered into the study. After randomization, 26 were assigned to the TMS group and 26 were assigned to the ceftriaxone group. Of the patients who completed the study, 13 of the TMS group had positive cultures at the time of initial presentation, and 20 of the ceftriaxone group had positive cultures. There was no statistical difference between the groups in symptoms of dysuria, hematuria, frequency, flank pain, and nocturia (alpha = .05). The physical parameters of age, blood pressure, pulse, and temperature were similar in the two groups (alpha = .05), as were the types of infecting organisms (alpha = .05). When comparing the two regimens, the ceftriaxone group cure rate (18 of 20, 90%) was not found to be significantly different from that of the TMS-treated control group (13 of 13) (alpha = .05).

Treatment of cutaneous abscess: a double-blind clinical study

Controversy exists about the value of antibiotic therapy following incision and drainage of cutaneous abscess. We undertook a randomized double-blind study to clarify the controversy. Adult patients with cutaneous abscesses who received outpatient surgical therapy were entered into the study. Following incision and drainage, patients received cephradine or placebo for seven days using a randomized code in a double-blind fashion. At the end of seven days, patients were reevaluated. Twenty-seven patients were treated with cephradine, and 23 with placebo. Ninety-six percent of the patients in each group were improved clinically after seven days. We conclude that cephradine did not alter the outcome of cutaneous abscesses at one week after incision and drainage. The implications are twofold: patients are not exposed to the potential side effects and allergic reactions of antibiotics, and the cost of health care can be reduced by not prescribing antibiotics in these patients.

Bilateral pneumothorax in an intravenous drug abuser

Pneumothorax is a condition commonly encountered by emergency physicians. Bilateral pneumothorax is a rare occurrence. We present a case of self-induced bilateral pneumothorax in an intravenous drug abuser. Causes of bilateral pneumothorax are reviewed.

Emergency phenytoin loading by constant intravenous infusion

We evaluated the efficacy of constant intravenous (IV) phenytoin infusion. Thirty-eight patients were evaluated prospectively for complications of continuous-infusion phenytoin loading. A total dose of 18 mg/kg was administered as a solution of 500 mg phenytoin in 50 mL normal saline using a constant infusion pump. The initial delivery rate was 40 mg/min. Cardiac rhythm was monitored by telemetry, and rhythm strips and vital signs were obtained every 15 minutes during infusion. Therapeutic phenytoin blood levels (greater than 10 micrograms/mL) were achieved in 37 patients (97%). Infusion was discontinued in one patient because of IV site irritation shortly after initiation of the infusion. Phenytoin levels in the toxic range were seen immediately postinfusion in 22 patients and in the four-hour postinfusion samples of 16 patients. Thirteen of 18 levels drawn 12 to 24 hours after infusion were therapeutic. Phenytoin levels greater than 20 micrograms/mL were tolerated without significant change in rhythm, QRS interval, or QT interval. A small statistically significant (P less than .05) decrease in systolic and mean arterial pressure was noted during the infusion. Complications included burning at the IV infusion site in four patients; the discomfort was relieved in three cases by reducing the rate of infusion to 20 mg/min. Seizures occurred in two patients during the infusion, requiring the additional use of diazepam or phenobarbital. Administration of a loading phenytoin dose by constant IV infusion is an effective means for achieving therapeutic levels quickly.

High carboxyhemoglobin level without acute or chronic findings

The clinical effects of carbon monoxide in humans have been well studied and described. Carboxyhemoglobin levels usually correlate with the degree of symptomatology; however, some investigators have noted that there may be a wide disparity between absolute carboxyhemoglobin levels and clinical status. A case is reported here of a young man with a potentially lethal level of carbon monoxide who developed neither significant symptomatology nor long-term sequelae. Until a more sensitive indicator of clinical outcome is found, clinicians must rely on carboxyhemoglobin levels and clinical history and examination to make treatment decisions, realizing that clinical presentation and absolute carboxyhemoglobin levels may correlate poorly.

Cutaneous abscesses: natural history and management in an outpatient facility

This study investigated the natural history and treatment of cutaneous abscesses in an outpatient setting. Incision, drainage, aerobic and anaerobic cultures were done on all 78 patients entered in the study. Tenderness and fluctuance were noted in more than 80% of the patients; erythema and induration in more than 60%. Forty-one percent of all abscesses were in the anogenital region. Forty-two percent of cultured abscesses grew aerobes exclusively, 28% grew anaerobes exclusively, and 27% grew a mixture of aerobes and anaerobes. The predominant aerobic organisms were Staphylococcus and Streptococcus, which were mostly isolated from the head/neck, extremities, and axillary regions. The predominant anaerobic organisms were Peptococcus and Bacteroides, which were primarily isolated from the anogenital regions. Nearly 60% of the patients returned for reevaluation. They were equally divided between those patients taking antibiotics and those not on antibiotics. However, all patients were clinically improved.

Transcutaneous cardiac pacing: determination of myocardial injury in a canine model

Transcutaneous cardiac pacing holds promise as the initial cardiac pacing technique for emergency patients. Determination of the extent of myocardial injury associated with the use of commercial transcutaneous pacemaker devices has been limited. This study was undertaken to document electrocardiographic, enzymatic, and histologic changes following transcutaneous pacing. Ten mongrel dogs were paced with a transcutaneous cardiac pacemaker for 30 minutes. Electrical pulses of 100 mA lasting 20 ms each were delivered at a rate of 80/min via cutaneous electrodes on the anterior and posterior thorax. Myocardial damage was assessed by serial electrocardiograms (ECGs), serial creatine kinase (CK) determinations with myocardial band (MB) fractionation, and gross and microscopic pathologic examination. Double blind reading of the ECGs showed no significant changes after pacing. CK levels peaked an average of 78 units over baseline levels at 4 hours; however, there was no rise in the CK MB fraction. Pathologic examination revealed micro-infarcts adjacent to intramural vessels in 5 animals, but no clinically significant myocardial injury in the 10 dogs. The absence of enzymatic, cardiographic, and clinically significant pathologic findings was statistically significant (P less than .05). Transcutaneous pacing at low currents and for short periods appears to be a safe technique. This pacing technique deserves further evaluation, and may hold promise as a clinical tool during resuscitation.

Pilot study on disposition and pain relief after i.m. administration of meperidine during the day or night

Two groups (four patients each) of sickle cell anemia patients with severe pain were studied. One group comprised patients admitted to emergency unit in the morning (5:40 to 9:15) and the other patients admitted in the evening (18:53 to 22:50). All patients received intramuscular meperidine (1.5 mg/kg). Pain intensity and pain relief were followed for 4 h; blood samples were taken up to 6 h after drug administration. Significant differences in drug disposition were found between the day and night groups, as the elimination half-life was 46% shorter during the night and the total serum clearance was 70% greater during the night. Whereas a positive correlation was found between drug concentration and pain relief for the day group, no such correlation was found for th night group. Even though peak concentrations were higher during the night, analgesia was lower. This pilot study suggests that much higher meperidine doses might be required during the night to achieve equieffective analgesia.

Male sexual assault

Reported cases of sexual assault in the United States increased 21% from 1974 to 1978. Recent literature discusses the medical, legal, and psychological management of the female sexual assault victim, but little has been written regarding appropriate management of male sexual assault. Twenty-nine male sexual assault victims were examined at University Hospital from 1976 to 1980. This study reviews evidence of genital and extragenital trauma and the percentage of those requiring gonorrhea prophylaxis. It further studies the background and characteristics of the sexual assault victim, characterization of the assailant, as well as the details and time of the assault. Information concerning male sexual assault and the unique problems associated with this group is scarce. This study is intended to aid in the development of an effective protocol in dealing with this group of patients and to sensitize physicians to this group of patients.

Experimental design for study of cardiopulmonary resuscitation in dogs

Many different designs for studies of various aspects of cardiopulmonary resuscitation (CPR) in dogs are described in the literature. No single technique is generally accepted. We present a systematized approach to the study of CPR in the canine model. Cardiac output, arterial blood pressure, and electrocardiogram were recorded for three different methods. The methods studied were closed chest compression, closed chest compression with an automatic gas-powered chest compressor, and open chest manual cardiac massage. Cardiac output for both types of external chest compression were less than 17% of control in all cases. With open chest cardiac massage, systemic arterial blood pressures were in the 50 mm Hg to 100 mm Hg range and cardiac output of up to 70% of control was achieved. Using a metronome to obtain compression rate and the arterial blood pressure to guide the efficacy of compression, consistent levels of cardiac output could be achieved for up to 30 minutes using open chest cardiac massage. Closed chest massage in man results in a cardiac output of 25% to 30% of normal when performed under optimal conditions. A cardiac output of 25% to 30% of control cannot be achieved in large dogs with external chest compression, and hence is not a good model to stimulate CPR in man.

Lidocaine levels during CPR: differences after peripheral venous, central venous, and intracardiac injections

Drug administration via peripheral vein, central vein, and intracardiac routes is generally assumed to be equally effective during cardiopulmonary resuscitation (CPR). Experiments were performed in an animal model to evaluate this assumption. Twelve mongrel dogs weighing greater than 20 kg were studied. Arterial blood pressure and electrocardiogram were monitored continuously. Cardiac outputs were evaluated before CPR to determine control. After thoracotomy and fibrillation of the heart, cardiac massage was started and the rate of compression adjusted to give 30% of control cardiac output. A lidocaine bolus of 1.5 mg/kg was given via peripheral vein in four dogs, central vein in four dogs, and intracardiac (left ventricle) in four dogs. Drug levels were sampled through an aortic catheter at the level of the coronary artery ostia every 20 sec for five min, every 30 sec for 10 min, and every 60 sec for 15 min. There was no significant difference in the appearance of effective levels or time of peak levels in the three groups. The peak levels were highest in the central venous group, while peripheral venous and intracardiac peak levels were 63% and 31%, respectively, of the central venous peak. Duration of effective levels was 20 min in the intracardiac group, 14.5 min in the central venous group, and 9.6 min in the peripheral venous group. Further studies are needed to determine whether changes are needed in drug administration during CPR in man.

Physostigmine--its use and abuse

Physostigmine salicylate, a cholinesterase inhibitor, has been shown to reverse the effects of certain drugs with anticholinergic properties. The paper provides a brief historical account of physostigmine, reviews the cholinergic drugs and their effects and suggests a management protocol based on physiologic criteria. Twenty-six overdose cases, recently treated with physostigmine, are summarized. The controversy regarding the etiology of seizures following physostigmine administration is discussed.