The role of environmental variation in mediating fitness trade-offs for an amphibian polyphenism

Fitness trade-offs are a foundation of ecological and evolutionary theory because trade-offs can explain life history variation, phenotypic plasticity, and the existence of polyphenisms. Using a 32-year mark-recapture dataset on lifetime fitness for 1093 adult Arizona tiger salamanders (Ambystoma mavortium nebulosum) from a high elevation, polyphenic population, we evaluated the extent to which two life history morphs (aquatic paedomorphs vs. terrestrial metamorphs) exhibited fitness trade-offs in breeding and body condition with respect to environmental variation (e.g. climate) and internal state-based variables (e.g. age). Both morphs displayed a similar response to higher probabilities of breeding during years of high spring precipitation (i.e. not indicative of a morph-specific fitness trade-off). There were likely no climate-induced fitness trade-offs on breeding state for the two life history morphs because precipitation and water availability are vital to amphibian reproduction. Body condition displayed a contrasting response for the two morphs that was indicative of a climate-induced fitness trade-off. While metamorphs exhibited a positive relationship with summer snowpack conditions, paedomorphs were unaffected. Fitness trade-offs from summer snowpack are likely due to extended hydroperiods in temporary ponds, where metamorphs gain a fitness advantage during the summer growing season by exploiting resources that are unavailable to paeodomorphs. However, paedomorphs appear to have the overwintering fitness advantage because they consistently had higher body condition than metamorphs at the start of the summer growing season. Our results reveal that climate and habitat type (metamorphs as predominately terrestrial, paedomorphs as fully aquatic) interact to confer different advantages for each morph. These results advance our current understanding of fitness trade-offs in this well-studied polyphenic amphibian by integrating climate-based mechanisms. Our conclusions prompt future studies to explore how climatic variation can maintain polyphenisms and promote life history diversity, as well as the implications of climate change for polyphenisms.

Air temperatures over-predict changes to stream fish assemblages with climate warming compared with water temperatures

Studies predicting how the distribution of aquatic organisms will shift with climate change often use projected increases in air temperature or water temperature. However, the assumed correlations between water temperature change and air temperature change can be problematic, especially for mountainous, high elevation streams. Using stream fish assemblage data from 1,442 surveys across a mountain-plains gradient (Wyoming, USA; 1990-2018), we compared the responsiveness of thermal guilds, native status groups, and assemblage structure to projected climate warming from generalized air temperature models and stream-specific water temperature models. Air temperature models consistently predicted greater range shift differences between warm-water and cold-water species, with air temperatures predicting greater increases in occurrence and greater range expansions for warm-water species. The "over-prediction" of warm-water species expansions resulted in air temperature models predicting higher rates of novel species combinations, greater increases in local species richness, and higher magnitudes of biotic homogenization compared with water temperature models. Despite differences in model predictions for warm-water species, both air and water temperature models predicted that three cold-water species would exhibit similar decreases in occurrence (decline of 1.0% and 1.8% of sites per 1°C warming, respectively) and similar range contractions (16.6 and 21.5 m elevation loss per 1°C warming, respectively). The "over-prediction" for warm-water species is partially attributable to water temperatures warming at slower rates than air temperatures because local, stream-scale factors (e.g., riparian cover, groundwater inputs) buffer high elevation streams from rising air temperatures. Our study provides the first comparison of how inferences about climate-induced biotic change at the species- and assemblage-levels differ when modeling with generalized air temperatures versus stream-specific water temperatures. We recommend that future studies use stream-specific water temperature models, especially for mountainous, high elevation streams, to avoid the "over-prediction" of biotic changes observed from air temperature variables.

Assessment of Long-Term Trends in Fish Distributions at Multiple Scales Decreases Uncertainty Associated with Historical Datasets

Monitoring long-term changes in aquatic biodiversity requires the effective use of historical data that were collected with different methods and varying levels of effort. Aggregating data into different spatial scales can control for such differences and provide a robust framework for monitoring distribution trends. We used a quantitative, multi-scale assessment to evaluate the potential drivers of distribution change for 60 fish species at three spatial scales, using 503 unique sampling events conducted between 1931 and 2019 in a stream biodiversity hotspot (French Creek, Pennsylvania, U.S.A). Trends delineated at multiple scales demonstrated that only one cyprinid species consistently declined through time. In contrast, several species, particularly centrarchids (bass and sunfish), appeared to increase with time. However, evidence for species' increases varied among the different spatial scales, and our observations suggest that differences in effort and detection across time periods may contribute to patterns of species increases. There was agreement among scales that agricultural land use, non-native brown trout (Salmo trutta), and anthropogenic barriers did not explain patterns in biodiversity change from the distribution trends in this study. The lack of species declines is likely due to the limited levels of historical impacts in the watershed compared with other locations in the region that experienced more acute pollution bottlenecks. Species increases were most prevalent for sportfish and baitfish species, suggesting that distribution increases were human mediated. Similar multi-scale assessments should provide more robust insight into patterns of biodiversity loss and distribution changes by maximizing the use of historical data.

Seasonal differences in climate change explain a lack of multi-decadal shifts in population characteristics of a pond breeding salamander

There is considerable variation among studies that evaluate how amphibian populations respond to global climate change. We used 23 years of annual survey data to test whether changes in climate have caused predictable shifts in the phenology and population characteristics of adult spotted salamanders (Ambystoma maculatum) during spring breeding migrations. Although we observed year-to-year correlation between seasonal climate variables and salamander population characteristics, there have not been long-term, directional shifts in phenological or population characteristics. Warm winters consistently resulted in early migration dates, but across the 23-year study, there was no overall shift towards warmer winters and thus no advanced migration timing. Warm summers and low variability in summer temperatures were correlated with large salamander body sizes, yet an overall shift towards increasing body sizes was not observed despite rising summer temperatures during the study. This was likely due to the absence of long-term changes of within-year variation in summer temperatures, which was a stronger determinant of body size than summer temperature alone. Climate-induced shifts in population characteristics were thus not observed for this species as long-term changes in important seasonal climate variables were not observed during the 23-years of the study. Different amphibian populations will likely be more resilient to climate change impacts than others, and the probability of amphibians exhibiting long-term population changes will depend on how seasonal climate change interacts with a species’ life history, phenology, and geographic location. Linking a wide range of seasonal climatic conditions to species or population characteristics should thus improve our ability for explaining idiosyncratic responses of species to climate change.

Measurement of Heavy Ion Irradiation Induced In-Plane Strain in Patterned Face-Centered-Cubic Metal Films: An in Situ Study

Nanocrystalline Ag, Cu, and Ni thin films and their coarse grained counterparts are patterned using focused ion beam and then irradiated by Kr ions within an electron microscope at room temperature. Irradiation induced in-plane strain of the films is measured by tracking the location of nanosized holes. The magnitude of the strain in all specimens is linearly dose-dependent and the strain rates of nanocrystalline metals are significantly greater as compared to that of the coarse grained metals. Real-time microscopic observation suggests that substantial grain boundary migration and grain rotation are responsible for the significant in-plane strain.

In situ study of defect migration kinetics and self-healing of twin boundaries in heavy ion irradiated nanotwinned metals

High energy particles introduce severe radiation damage in metallic materials, such as Ag. Here we report on the study on twin boundary (TB) affected zone in irradiated nanotwinned Ag wherein time accumulative defect density and defect diffusivity are substantially different from those in twin interior. In situ studies also reveal surprising resilience and self-healing of TBs in response to radiation. This study provides further support for the design of radiation-tolerant nanotwinned metallic materials.

Elastic trapping of dislocation loops in cascades in ion-irradiated tungsten foils

Using in situ transmission electron microscopy (TEM), we have observed nanometre scale dislocation loops formed when an ultra-high-purity tungsten foil is irradiated with a very low fluence of self-ions. Analysis of the TEM images has revealed the largest loops to be predominantly of prismatic 1/2〈111〉 type and of vacancy character. The formation of such dislocation loops is surprising since isolated loops are expected to be highly mobile, and should escape from the foil. In this work we show that the observed size and number density of loops can be explained by the fact that the loops are not isolated-the loops formed in close proximity in the cascades interact with each other and with vacancy clusters, also formed in cascades, through long-range elastic fields, which prevent the escape of loops from the foil. We find that experimental observations are well reproduced by object Kinetic Monte Carlo simulations of evolution of cascades only if elastic interaction between the loops is taken into account. Our analysis highlights the profound effect of elastic interaction between defects on the microstructural evolution of irradiated materials.

Reactive skin decontamination lotion (RSDL) for the decontamination of chemical warfare agent (CWA) dermal exposure

Rapid decontamination of the skin is the single most important action to prevent dermal absorption of chemical contaminants in persons exposed to chemical warfare agents (CWA) and toxic industrial chemicals (TICs) as a result of accidental or intentional release. Chemicals on the skin may be removed by mechanical means through the use of dry sorbents or water. Recent interest in decontamination systems which both partition contaminants away from the skin and actively neutralize the chemical has led to the development of several reactive decontamination solutions. This article will review the recently FDA-approved Reactive Skin Decontamination Lotion (RSDL) and will summarize the toxicity and efficacy studies conducted to date. Evidence of RSDL's superior performance against vesicant and organophosphorus chemical warfare agents compared to water, bleach, and dry sorbents, suggests that RSDL may have a role in mass human exposure chemical decontamination in both the military and civilian arenas.

High-fidelity simulation is superior to case-based discussion in teaching the management of shock

BACKGROUND

Case-based discussion (CBD) is an established method for active learning in medical education. High-fidelity simulation has emerged as an important new educational technology. There is limited data from direct comparisons of these modalities.

AIMS

The primary purpose of this study was to compare the effectiveness of high-fidelity medical simulation with CBD in an undergraduate medical curriculum for shock.

METHODS

The subjects were 85 third-year medical students in their required surgery rotation. Scheduling circumstances created two equal groups. One group managed a case of septic shock in simulation and discussed a case of cardiogenic shock, the other group discussed septic shock and experienced cardiogenic shock through simulation. Student comprehension of the assessment and management of shock was then evaluated by oral examination (OE).

RESULTS

Examination scores were superior in all comparisons for the type of shock experienced through simulation. This was true regardless of the shock type. Scores associated with patient evaluation and invasive monitoring, however, showed no difference between groups or in crossover comparison.

CONCLUSIONS

In this study, students demonstrated better understanding of shock following simulation than after CBD. The secondary finding was the effectiveness of an OE with just-in-time deployment in curriculum assessment.

Termination of drug-induced torsades de pointes with overdrive pacing

Drug-induced prolongation of the QT interval is frequently encountered after medication overdose. Such toxicity can result in degeneration to torsades de pointes (TdP) and require overdrive pacing. We present 3 cases in which intentional medication overdose resulted in QTc prolongation with subsequent degeneration to TdP. Despite appropriate care, including magnesium therapy, each case required overdrive pacing for resolution of TdP. Although rarely encountered, patients with drug-induced TdP can be successfully managed with overdrive pacing.

Preparation of TEM samples of ferritic alloys

We describe techniques for electropolishing irradiated ferritic specimens for examination under the TEM in situations where the foil quality is of utmost importance. First, we describe some modifications to the standard technique for making plan-view specimens aimed at optimizing the foil quality. Second, we describe a technique for making plan-view specimens from a region of buried damage in a specimen irradiated with 2 MeV Fe(+) ions.

Atypical antipsychotics and newer antidepressants

Atypical antipsychotics and newer antidepressants are commonly prescribed medications responsible for tens of thousands of adverse drug exposures each year. The emergency medicine physician should have a basic understanding of the pharmacology and toxicity of these agents. This knowledge is crucial to providing proper care and timely management of patients presenting with adverse drug effects from exposure to atypical antipsychotics and newer antidepressants.

Chemical Terrorism Attacks: Update on Antidotes

There is well-founded concern that a chemical or radioactive agent will at some point be used as a weapon of terror. There are several antidotes that, if used correctly in a timely fashion, can help lessen the harm caused by these agents. This article is meant to introduce the clinician to several such agents, along with the antidotes useful in the management of exposure to these. It covers the indications, administration, and precautions for using these antidotes.

Poison Centers as Information Resources for Volunteer EMS in a Suspected Chemical Exposure

In the early part of chemical terrorism or hazardous materials events, protective actions and patient care require empirical decisions because reliable and accurate information may not be readily available. It has become increasingly important to identify reliable information resources that are the most likely to be accessed for information during these events. We sought to identify information resources that volunteer Emergency Medical Services (EMS) providers would use during a suspected chemical exposure. Survey questionnaires were completed by 116 of 151 (76.8%) suburban and rural EMS providers. In the past 12 months, most participants used medical journals and textbooks (59.5%), internet sites (57.8%), and poison centers (55.2%) as information resources. For two hypothetical scenarios involving chemical exposures, poison centers were most frequently chosen as likely contacts for information regarding the identity of the agent (case 1: 52.6%, case 2: 48.3%), treatment (74.1%, 64.7%, respectively), and antidote (59.5%, 49.1%, respectively). Fire department hazardous materials team tied with poison centers as the highest for chemical agent in the second scenario (48.3%) and was ranked highest both for decontamination (75.0%, 64.7%, respectively) and personal protection (56.9%, 45.7%, respectively). Poison centers were selected as the best resource for timely information (70.7%), availability (69.0%), and ease of contact (72.4%), and second highest for knowledge of chemical agents (44.0%), after CHEMTREC (56.9%). Finally, poison centers and CHEMTREC received the highest overall ratings (28.4% and 26.7%, respectively). Poison centers are viewed as an important information resource by EMS providers and may be the most commonly sought resource for various information needs during a suspected chemical exposure.

Bringing Order Out of Chaos: Effective Strategies for Medical Response to Mass Chemical Exposure

An accident or a deliberate terrorism attack releasing hazardous chemicals will create chaos, confusion, and seeming unpredictability that complicates the emergency response. Clinicians are challenged to urgently treat patients needing care, even before a chemical is confirmed. Emergency response planning that focuses on preparing for predictable challenges to the health care system and applies basic toxicologic principles to clinical decision-making can bring a sense of order to the chaos and provide medical care that will be best for the most victims of an incident.

Acetaminophen Poisoning

Acetaminophen (acetyl-para-amino-phenol or APAP), an antipyretic and analgesic, is a common component in hundreds of over-the-counter and prescription medications. The wide usage of this drug results in many potentially toxic exposures. It is therefore critical for the clinician to be comfortable with the diagnosis and treatment of APAP toxicity. Prompt recognition of APAP overdose and institution of appropriate therapy are essential to preventing morbidity and mortality.

Updates on acetaminophen toxicity

APAP is likely to remain a common toxic exposure and continue to cause significant morbidity and mortality. To minimize the harm to patients, it is necessary for the clinician to be aware of the current diagnostic and therapeutic management of APAP poisoning. Despite the bulk of literature on APAP, management strategies are likely to continue to change as more studies are conducted to improve our understanding of nonacute ingestions and the role of prognostic markers in defining those most at risk for life-threatening hepatotoxicity.

Perceived poisons

Perceived poisoning may manifest in numerous ways; however, all cases share certain characteristics. All are fostered by the wide availability of unreliable information about chemical safety, poor understanding of scientific principles, and ineffective risk communication. Although this problem is still incompletely understood, some approaches have been demonstrated to be useful, such as education about risk, appropriate reassurance, and empathy on the part of the practitioner. Successful management may curtail the spread or exacerbation of symptoms, whereas unsuccessful treatment may cause the problems to escalate, with detrimental effects on both society and patient.

What is the rate of adverse events after oral N-acetylcysteine administered by the intravenous route to patients with suspected acetaminophen poisoning?

STUDY OBJECTIVE

We conduct a study to determine the rate of adverse events (anaphylactoid and cardiorespiratory) associated with the use of oral N-acetylcysteine by the intravenous route for the treatment of suspected acetaminophen poisoning and to examine specific variables that may be associated with adverse events.

METHODS

We conducted a retrospective medical record review with explicit criteria. All patients who received oral N-acetylcysteine by the intravenous route from September 1995 to September 2001 were included. Patients were identified by cross-matching 3 databases. Adverse events were divided into categories of cutaneous, systemic, or life threatening. Five reviewers abstracted charts by using a standardized data collection form. Interrater reliability was calculated by using 24 medical records abstracted by all 5 reviewers.

RESULTS

There were 7 adverse events identified in 187 patients (3.7%; 95% confidence interval 1.0% to 6.5%). Six adverse events were cutaneous and responded rapidly to antihistamines. One adverse event was life threatening but not clearly related to N-acetylcysteine. A high rate of antihistamine exposure (53%) was identified before the administration of N-acetylcysteine. Interrater agreement was higher than 95%.

CONCLUSION

Intravenous administration of an oral solution of N-acetylcysteine is associated with a low rate of adverse events and should be considered for selected patients with suspected acetaminophen poisoning.

Dimercaptosuccinic acid and Prussian Blue in the treatment of acute thallium poisoning in rats

INTRODUCTION

Despite being banned as a pesticide, thallium still results in human and animal poisonings. Current recommended treatments include the use of the chemical Prussian Blue. Limitations in its availability may result in Prussian Blue not being obtainable in the thallium-poisoned patient. The chelator 2,3-Dimercaptosuccinic acid (DMSA) is currently FDA-approved for use in childhood lead poisoning and has been reported to be beneficial in treating other heavy metal poisonings. The objective of this study was to determine the efficacy of DMSA as a treatment for thallium poisoning by studying mortality and whole-brain concentrations in thallium poisoned rats.

MATERIAL AND METHODS

Rats were gavaged with 30 mg/kg of thallium. After 24 hours they were randomized to DMSA (n = 20) 50 mg/kg twice daily for 5 days, Prussian Blue (n = 20) 50 mg/kg twice daily for 5 days, or control (n = 30). Animals were monitored twice daily for weight loss and mortality. Animals losing greater than 20% of their starting weight were euthanized and counted as a mortality. All surviving rats at 120 hours had their brains harvested and digested and underwent subsequent thallium analysis.

RESULTS

The rate of survival in DMSA-treated animals compared to control was 45% vs. 21%, p = 0.07. Mean whole-brain thallium concentrations between DMSA and control rats were 3.4 vs. 3.0 microg/g, p = 0.06. Prussian Blue-treated rats had significantly improved survival (70% vs. 21%, p < 0.01) and lower whole-brain thallium concentrations (1.6 vs. 3.0 microg/g, p < 0.01 tissue) compared to controls.

CONCLUSION

DMSA failed to reduce brain thallium concentrations in rats poisoned with thallium and had an indeterminate effect on mortality while Prussian Blue significantly reduces both brain thallium concentrations and mortality.

Intrathecal baclofen withdrawal mimicking sepsis

Baclofen (Lioresal) is a drug of choice to treat spasticity and is increasingly being administered intrathecally via an implantable pump in cases refractory to oral therapy. Emergency physicians will likely treat patients with baclofen withdrawal or overdose as this treatment becomes more widespread. The syndrome of baclofen withdrawal presents with altered mental status, fever, tachycardia, hypertension or hypotension, seizures, and rebound spasticity, and may be fatal if not treated appropriately. Baclofen withdrawal may mimic other diseases including sepsis, meningitis, autonomic dysreflexia, malignant hyperthermia, or neuroleptic malignant syndrome. Treatment consists of supportive care, reinstitution of baclofen, benzodiazepines, and diagnosis and eventual repair of intrathecal pump and catheter malfunction.

Droperidol, QT prolongation, and sudden death: what is the evidence?

STUDY OBJECTIVE

Droperidol is a butyrophenone commonly used as an antiemetic and antipsychotic in the United States since US Food and Drug Administration (FDA) approval in 1970. Its labeling has recently been revised, with a black box warning for cases of QT prolongation leading to torsades de pointes and death. A black box warning is applied when serious adverse drug reactions are uncovered for medications. We sought to examine the evidence of a causal association suggested by the black box warning to aid clinicians in their risk-benefit analyses regarding further use of droperidol.

METHODS

A literature search was undertaken to determine the evidence regarding the association between droperidol and QT prolongation or torsades de pointes. The evidence was then evaluated by using evidence-based medicine principles. In addition, a review of the FDA regulatory process is presented.

RESULTS

Three clinical studies, 1 published abstract, and 7 case reports were reviewed. Available postmarketing surveillance data (MedWatch reports) were also reviewed. Applying the criteria of evidence-based medicine and Hill's criteria, the evidence is not convincing for a causal relationship between therapeutic droperidol administration and life-threatening cardiac events.

CONCLUSION

The recent black box warning appears to have originated from postmarketing surveillance data rather than data reported in the peer-reviewed medical literature. Ongoing monitoring of drug safety and more definitive study appear appropriate.

Hyperbaric oxygen therapy in acute ischemic stroke: results of the Hyperbaric Oxygen in Acute Ischemic Stroke Trial Pilot Study

BACKGROUND AND PURPOSE

Hyperbaric oxygen therapy (HBO) has promise as a treatment for acute stroke. This study was conducted to evaluate the efficacy, safety, and feasibility of using HBO in acute ischemic stroke.

METHODS

We conducted a randomized, prospective, double-blind, sham-controlled pilot study of 33 patients presenting with acute ischemic stroke who did not receive thrombolytics over a 24-month period. Patients were randomized to treatment for 60 minutes in a monoplace hyperbaric chamber pressurized with 100% O2 to 2.5-atm absolute (ATA) in the HBO group or 1.14 ATA in the sham group. Primary outcomes measured included percentage of patients with improvement at 24 hours (National Institutes of Health Stroke Scale [NIHSS]) and 90 days (NIHSS, Barthel Index, modified Rankin Scale, Glasgow Outcome Scale). Secondary measurements included complications of treatment and mortality at 90 days.

RESULTS

Baseline demographics were similar in both groups. There were no differences between the groups at 24 hours (P=0.44). At 3 months, however, a larger percentage of the sham patients had a good outcome defined by their stroke scores compared with the HBO group (NIHSS, 80% versus 31.3%; P=0.04; Barthel Index, 81.8% versus 50%; P=0.12; modified Rankin Scale, 81.8% versus 31.3%; P=0.02; Glasgow Outcome Scale, 90.9% versus 37.5%; P=0.01) with loss of statistical significance in a intent-to-treat analysis.

CONCLUSIONS

Although our HBO protocol appears feasible and safe, it does not appear to be beneficial and may be harmful in patients with acute ischemic stroke.

Thallium and arsenic poisoning in a small midwestern town

Thallium and arsenic have been used as a means of criminal poisoning. Although both manifest characteristically with peripheral neuropathies, thallium is associated with alopecia and arsenic with gastrointestinal symptoms. We describe the symptoms, physical findings, diagnostic test results, and outcomes in a group of men poisoned with thallium and arsenic. Seven patients had evidence of elevated thallium levels, and 2 patients had elevated arsenic and thallium levels. The most commonly reported symptoms included myalgias, arthralgias, paresthesias, and dysesthesias. Five patients developed alopecia. All patients with symptoms and peripheral neuropathies had characteristic blackening of their hair roots. Initially treated with dimercaptosuccinic acid, patients were switched to multiple-dose activated charcoal after testing revealed thallium poisoning. By 6 months, all patients' symptoms and peripheral neuropathies improved, but 5 patients had ongoing psychiatric problems. Thallium remains a means of criminal poisoning and should be considered in any patient with a rapidly progressing peripheral neuropathy with or without alopecia.

Organ procurement and successful transplantation after malathion poisoning

BACKGROUND

One of the major limitations to organ procurement and donation is the lack of suitable donors. As the demand for suitable organs exceeds the supply, identification of potential donors continues to evolve. Due to perceived risks of transmittable toxins and insufficient understanding of toxicological fate, poisoned patients are often overlooked as organ donors.

CASE REPORT

A 17-year-old white male was found by his mother having a seizure in bed. A strong odor of pesticides was noted and an empty container of malathion was found. He was transported to an outlying hospital and underwent prolonged cardiopulmonary resuscitation. The patient exhibited symptoms consistent with cholinergic poisoning and received a total of 12 mg of atropine and a pralidoxime bolus of 1 g followed by an infusion at 500 mg/h. Initial plasma cholinesterase was 1433 IU/L (normal 7500-14,600). The patient developed aspiration pneumonia and remained comatose. No further treatment for cholinergic toxicity was needed 5 days after admission and a cerebral blood flow scan confirmed brain death. After review of the available literature on the disposition andfate of malathion in human tissues, the patient's liver and kidneys were harvested for transplantation. The recipients were all doing well 1 year posttransplantation.

CONCLUSIONS

This case of successful transplantation after organophosphate exposure underscores the fact that poisoned patients should not be overlooked as transplant candidates. Decisions should be based on the clinical presentation and knowledge of the properties of the toxin.

A pilot study to assess the safety of dobutamine stress echocardiography in the emergency department evaluation of cocaine-associated chest pain

STUDY OBJECTIVE

Chest pain in the setting of cocaine use poses a diagnostic dilemma. Dobutamine stress echocardiography (DSE) is a widely available and sensitive test for evaluating cardiac ischemia. Because of the theoretical concern regarding administration of dobutamine in the setting of cocaine use, we conducted a pilot study to assess the safety of DSE in emergency department patients with cocaine-associated chest pain.

METHODS

A prospective case series was conducted in the intensive diagnostic and treatment unit in the ED of an urban tertiary-care teaching hospital. Patients were eligible for DSE if they had used cocaine within 24 hours preceding the onset of chest pain and had a normal ECG and tropinin I level. Patients exhibiting signs of continuing cocaine toxicity were excluded from the study. All patients were admitted to the hospital for serial testing after the DSE testing in the intensive diagnostic and treatment unit.

RESULTS

Twenty-four patients were enrolled. Two patients had inadequate resting images, one DSE was terminated because of inferior hypokinesis, another DSE was terminated because of a rate-related atrial conduction deficit, and 1 patient did not reach the target heart rate. Thus, 19 patients completed a DSE and reached their target heart rates. None of the patients experienced signs of exaggerated adrenergic response, which was defined as a systolic blood pressure of greater than 200 mm Hg or the occurrence of tachydysrhythmias (excluding sinus tachycardia). Further suggesting lack of exaggerated adrenergic response, 13 (65%) of 20 patients required supplemental atropine to reach their target heart rates.

CONCLUSION

No exaggerated adrenergic response was detected when dobutamine was administered to patients with cocaine-related chest pain.

Sodium bicarbonate to correct widened QRS in a case of flecainide overdose

A 16-yr-old male attempted suicide by ingesting approximately 4000 mg of flecainide. He developed coma, hypotension, and ventricular tachycardia. In addition to supportive care and antidysrhythmics, he received intravenous sodium bicarbonate for the wide complex dysrhythmia. Animal studies and anecdotal human experience have suggested that increasing the extracellular sodium improves cardiac conduction in flecainide toxicity. The patient's QRS narrowed immediately following sodium bicarbonate infusion. Sodium bicarbonate may be useful in the treatment of widened QRS and ventricular ectopy resulting from flecainide toxicity.

Comparison of topical magnesium and calcium treatment for dermal hydrofluoric acid burns

STUDY OBJECTIVE

To compare topical preparations of magnesium and calcium in the treatment of dermal hydrofluoric acid burns.

DESIGN

A randomized, blinded, controlled animal model study.

SETTING

Animal care facility.

TYPE OF PARTICIPANTS

New Zealand rabbits.

INTERVENTIONS

Each rabbit was burned with hydrofluoric acid at four sites along the thoracolumbar spine. Equimolar amounts of calcium gluconate, magnesium gluconate, and a magnesium hydroxide antacid were added into a lubricating jelly. The jelly alone was a control preparation. After a water rinse, the burns were massaged with the gels for 1 minute five times; at 4 and 20 minutes and at 1, 4, and 24 hours. Each rabbit served as its own control by receiving all four treatments.

MEASUREMENTS AND MAIN RESULTS

Burn diameter and burn surface area diminished over time, but there were no statistically significantly differences among the treatments. Burn ranking and burn rating of severity also did not demonstrate differences. The histologic analysis of the burns, however, demonstrated that calcium gluconate-treated burns were less severe and more superficial than the control and magnesium gluconate-treated burns; the magnesium hydroxide antacid-treated burns were not statistically different compared to the calcium gluconate-treated burns.

CONCLUSION

Topical calcium gluconate is an efficacious treatment for dermal hydrofluoric acid burns. Further research is needed to determine the role of magnesium-containing antacids in the treatment of hydrofluoric acid burns.

Emergency department response to hazardous materials incidents

Emergency physicians must stay alert to situations that involve toxic chemical exposures. An appropriate response to victims of chemical contamination is important for the victim's outcome and the safety of hospital personnel. Successful management of such a situation requires managing information, resources, and patients with complex medical conditions. Chemical contamination may affect one or hundreds of victims. Community planning is essential for an effective response to toxic chemical accidents (Haz-Mat).

Cyanide and methemoglobin kinetics in smoke inhalation victims treated with the cyanide antidote kit

STUDY OBJECTIVE

To evaluate serial cyanide, methemoglobin, and carbon monoxide levels in smoke inhalation patients.

SETTING

Regional poison center and regional toxicology treatment center.

PARTICIPANTS

Seven critically ill smoke inhalation patients referred to the regional poison center.

INTERVENTIONS

Peak level and half-life were determined by obtaining serial carboxyhemoglobin, cyanide, and methemoglobin levels.

RESULTS

The mean observed half-life of cyanide was 3.0 +/- 0.6 hours. Methemoglobinemia was evaluated in four patients after sodium nitrite administration. The peak measured methemoglobin levels (mean, 10.5% +/- 2%; range, 7.9% to 13.4%) did not occur until a mean of 50 minutes (range, 35 to 70 minutes) following administration of sodium nitrite. The total oxygen-carrying capacity reduced by the combination of carboxyhemoglobin and methemoglobin was never more than 21% (range, 10% to 21%) in this series.

CONCLUSION

The administration of sodium nitrite to smoke inhalation patients in the presence of concomitant carbon monoxide poisoning may be relatively safe.