Cardiac Arrest in Special Populations.

Best practices in cardiac arrest depend on continuous high-quality chest compressions, appropriate ventilatory management, early defibrillation of shockable rhythms, and identification and treatment of reversible causes. Although most patients can be treated according to highly vetted treatment guidelines, some special situations in cardiac arrest arise where additional skills and preparation can improve outcomes. Situations covered in this section involve cardiac arrest in context of electrical injuries, asthma, allergic reactions, pregnancy, trauma, electrolyte imbalances, toxic exposures, hypothermia, drowning, pulmonary embolism, and left ventricular assist devices.

Evidence of a genetic background predisposing to complex regional pain syndrome type 1.

BACKGROUND: Complex regional pain syndrome type 1 (CRPS-1) is a rare, disabling and sometimes chronic disorder usually arising after a trauma. This exploratory study examined whether patients with chronic CRPS-1 have a different genetic profile compared with those who do not have the condition. METHODS: Exome sequencing was performed to seek altered non-synonymous SNP allele frequencies in a discovery cohort of well-characterised patients with chronic CRPS-1 (n=34) compared with population databases. Identified SNP alleles were confirmed by Sanger sequencing and sought in a replication cohort (n=50). Gene expression of peripheral blood macrophages was assessed. RESULTS: In the discovery cohort, the rare allele frequencies of four non-synonymous SNPs were statistically increased. The replication cohort confirmed this finding. In a chronic pain cohort, these alleles were not overexpressed. In total, 25 out of 84 (29.8%) patients with CRPS-1 expressed a rare allele. The SNPs were rs41289586 in ANO10, rs28360457 in P2RX7, rs1126930 in PRKAG1 and rs80308281 in SLC12A9. Males were more likely than females to have a rare SNP allele, 8 out of 14 (57.1%) vs 17 out of 70 (24.3%) (Fisher's p=0.023). ANO10, P2RX7, PRKAG1 and SLC12A9 were all expressed in macrophages from healthy human controls. CONCLUSION: A single SNP in each of the genes ANO10, P2RX7, PRKAG1 and SLC12A9 was associated with developing chronic CRPS-1, with more males than females expressing these rare alleles. Our work suggests the possibility that a permissive genetic background is an important factor in the development of CRPS-1.

Cardiac Arrest in Special Populations.

Best practices in cardiac arrest depend on continuous high-quality chest compressions, appropriate ventilatory management, early defibrillation of shockable rhythms, and identification and treatment of reversible causes. Although most patients can be treated according to highly vetted treatment guidelines, some special situations in cardiac arrest arise where additional skills and preparation can improve outcomes. Situations covered in this section involve cardiac arrest in context of electrical injuries, asthma, allergic reactions, pregnancy, trauma, electrolyte imbalances, toxic exposures, hypothermia, drowning, pulmonary embolism, and left ventricular assist devices.

Emergency department care of patients with Duchenne muscular dystrophy.

Patients with Duchenne muscular dystrophy are living longer and are increasingly seen in Emergency Departments. Though the most common cause of death remains progressive respiratory failure, increased life expectancies have unmasked the significance of progressive myocardial dysfunction, now associated with nearly 40% of mortalities in the DMD population. Cardiac complications such as arrhythmias and cardiomyopathy are becoming ever more widely recognized. Emergency physicians may encounter DMD patients with untreated, undiagnosed or worsening of known heart disease. This review will initially familiarize the emergency physician with the pathophysiology and lifetime trajectory of care for these patients before describing specific emergency department evaluation and treatment.

Provider Fatigue During Direct Manual Compression for Life-Threatening Bleeding.

Introduction Trauma is a leading cause of death throughout the world, with hemorrhage being responsible for more than 35% of pre-hospital trauma deaths and more than 40% of deaths within the first 24 hours after injury. Despite first aid having a demonstrable effect on mortality from trauma, relatively little research has compared the best methods for bleeding control in the prehospital first aid setting. The most common first-line therapy for external bleeding control in the pre-hospital first aid setting is direct manual compression (DMC). However, a prior study demonstrated that the primary cause of failure in a simulated model of life-threatening bleeding was the inability to maintain adequate direct pressure for three minutes. In this study, we evaluated the effect of fatigue on DMC for the duration of a typical urban emergency medical services (EMS) response time. Methods We conducted a prospective observational trial of 33 participants, 18 years of age or older to measure the pressure generated on a model of life-threatening bleeding over an eight-minute period using a "CPR posture" for applying pressure. The primary analyses were longitudinal two-level multilevel models (MLM) with repeated measures of outcome (i.e., CPR posture pressure) nesting within participants. The demographic factors of gender, age, and weight were included as moderators in the analyses and each was analyzed independently. Results The participants' average age was 31 (SD = 11) and the average weight was 161 pounds (SD = 31). The sample consisted of 18 female participants (54.5%) and 15 male participants (45.5%). Applied DMC pressure declined over time, more sharply initially from the beginning to approximately 250 seconds, at which point the decrease in pressure was gradual. Of the demographic factors, gender was associated with a difference in cardiopulmonary resuscitation (CPR) posture pressure over time. Conclusion Rescuers should be aware that fatigue may occur and may affect the quality of direct manual compression for control of life-threatening bleeding. Further research is needed to define the external pressures needed to control life-threatening bleeding and the extent that rescuer fatigue affects this pressure.

Opioid Prescribing: Where Should Academic Emergency Departments Focus Their Efforts?

BACKGROUND: Opioid prescriptions from the emergency department (ED) are being heavily scrutinized. This has resulted in prescribing guidelines and laws. OBJECTIVE: We analyzed the "current state" of opioid prescribing practices by emergency medicine (EM) trainees to gain understanding where operational, educational, or supervisory efforts should be directed to comply with current guidelines and future legislation. METHODS: Our retrospective, observational, study was performed at an academic ED with an annual census of 61,289 visits. We extracted all 6962 opioid prescriptions attributed to the ED during calendar year 2015 from the electronic health record. Error prescriptions were excluded from the analysis. Overall prescribing by opioid class was performed. Prescriptions written by EM trainees were categorized by postgraduate year and compared with other prescribers. Prescribing patterns for recurrent visits were also analyzed. RESULTS: Of the 6962 opioid discharge prescriptions, 5515 were written by EM providers. No refills were provided. A mean of 15.4 pills (95% confidence interval 13.9-16.9) were prescribed. Analysis of variance did not detect a significant difference between mean numbers of pills prescribed by EM providers. However, there was a significant difference between EM and non-EM prescribers. Less-experienced EM providers exhibited greater variability with regard to class and preparation. There were 389 prescriptions written for patients who received at least one other opioid prescription in the preceding 30 days. The number of pills dispensed decreased with increasing prior visits. CONCLUSION: EM providers prescribe short courses of opiates regardless of postgraduate year. Patients returning to the ED received fewer pills on subsequent visits. Non-EM providers prescribe larger numbers of pills per prescription. This information will help focus future operational efforts and educational efforts to comply with guidelines and laws.

Comparison of viral load in individuals with and without asthma during infections with rhinovirus.

RATIONALE: Most virus-induced attacks of asthma are caused by rhinoviruses (RVs). OBJECTIVES: To determine whether people with asthma are susceptible to an increased viral load during RV infection. METHODS: Seventy-four children (4-18 yr old) were enrolled; 28 with wheezing, 32 with acute rhinitis, and 14 without respiratory tract symptoms. Nasal washes were evaluated using quantitative polymerase chain reaction for RV to judge viral load along with gene sequencing to identify strains of RV. Soluble intercellular adhesion molecule-1, IFN-λ1, and eosinophil cationic protein in nasal washes, along with blood eosinophil counts and total and allergen-specific IgE in sera, were also evaluated. Similar assessments were done in 24 young adults (16 with asthma, 8 without) who participated in an experimental challenge with RV (serotype 16). MEASUREMENTS AND MAIN RESULTS: Fifty-seven percent of wheezing children and 56% with acute rhinitis had nasal washes testing positive for RV. The geometric mean of viral loads by quantitative polymerase chain reaction in washes from wheezing children was 2.8-fold lower, but did not differ significantly from children with rhinitis (7,718 and 21,612 copies of viral RNA per microliter nasal wash, respectively; P = 0.48). The odds for wheezing were increased if children who tested positive for RV were sensitized to one or more allergens (odds ratio, 3.9; P = 0.02). Similarly, neither peak nor cumulative viral loads differed significantly in washes from adults with asthma compared with those without asthma during the experimental RV challenge. CONCLUSIONS: During acute symptoms, children infected with RV enrolled for wheezing or acute rhinitis had similar viral loads in their nasal washes, as did adults with and without asthma infected with RV-16 experimentally.

The wire is really easy to see (WIRES): sonographic visualization of the guidewire by novices.

OBJECTIVE: To determine whether novices can distinguish between properly and improperly placed guidewires in a vascular access model after only minimal training. METHODS: This was a prospective study involving trainees with no previous training in sonographic guidewire visualization. A vascular access model was created with guidewires positioned inside or adjacent to simulated veins. Subjects were taught to scan each wire to determine its location. Afterward, participants scanned a test model of five vein-wire pairs and recorded their answers as "inside," "outside," or "unsure." The test characteristics of sonographic guidewire localization were determined using actual wire location as the criterion standard. RESULTS: Forty trainees (21 emergency medicine residents, 19 medical students) participated, and each examined five simulated veins. There were 156 true positives (intravascular wire correctly identified), 38 true negatives (extravascular wire correctly identified), 2 false negatives, 2 false positives, and 2 cases in which the participant marked "not sure," which were reclassified as false negatives. Test characteristics were sensitivity 97.5% (95% CI 93.3-99.2) and specificity 95.0% (95% CI 81.8-99.1). The overall accuracy was 97.0%. CONCLUSIONS: Sonographic guidewire visualization, a step recommended for ensuring proper vessel cannulation during central venous access, can be accomplished by novices with a high degree of accuracy.

Brain injury risk from primary blast.

BACKGROUND: Military service members are often exposed to at least one explosive event, and many blast-exposed veterans present with symptoms of traumatic brain injury. However, there is little information on the intensity and duration of blast necessary to cause brain injury. METHODS: Varying intensity shock tube blasts were focused on the head of anesthetized ferrets, whose thorax and abdomen were protected. Injury evaluations included physiologic consequences, gross necropsy, and histologic diagnosis. The resulting apnea, meningeal bleeding, and fatality were analyzed using logistic regressions to determine injury risk functions. RESULTS: Increasing severity of blast exposure demonstrated increasing apnea immediately after the blast. Gross necropsy revealed hemorrhages, frequently near the brain stem, at the highest blast intensities. Apnea, bleeding, and fatality risk functions from blast exposure to the head were determined for peak overpressure and positive-phase duration. The 50% risk of apnea and moderate hemorrhage were similar, whereas the 50% risk of mild hemorrhage was independent of duration and required lower overpressures (144 kPa). Another fatality risk function was determined with existing data for scaled positive-phase durations from 1 millisecond to 20 milliseconds. CONCLUSION: The first primary blast brain injury risk assessments for mild and moderate/severe injuries in a gyrencephalic animal model were determined. The blast level needed to cause a mild/moderate brain injury may be similar to or less than that needed for pulmonary injury. The risk functions can be used in future research for blast brain injury by providing realistic injury risks to guide the design of protection or evaluate injury.

Pediatric resuscitation and cardiac arrest.

Cardiac arrest in children is, fortunately, a relatively infrequent event. Mortality rate after cardiac arrest is greater than 50%. This article discusses strategies to increase the chance of survival to discharge. These strategies focus on suggestions for organizing a system prepared to care for critically ill children, incorporating the 2010 American Heart Association resuscitation guidelines into clinical practice, and encouraging physicians to become advocates of decreasing the occurrence of pediatric cardiac arrest. Providing the best-prepared system available to care for critically ill children will, it is hoped, decrease the number of preventable deaths in children.

Metabolic rate variation over adult lifetime in the butterfly Vanessa cardui (Nymphalidae: Nymphalinae): aging, feeding, and repeatability.

Questions about the adaptive importance of metabolic rate can be approached only when measurements of differences between individuals are repeatable. We made daily measurements of CO(2) production, body mass, and food uptake over the adult life span of unmated Vanessa cardui kept under constant environmental conditions in both fed and unfed treatments. Mass and CO(2) production generally declined with age in both treatments, though with much day-to-day variability in the fed treatment. For the full samples, metabolic rate was repeatable for the unfed treatment (repeatability r = 0.60) but not for the fed treatment (r = 0.03). Differences between fed and unfed individuals of the same age range were repeatable for the unfed treatment (r = 0.39) but not for the fed treatment (r = -0.20). Removing age effects on CO(2) production yielded still higher repeatability in the unfed treatment (r = 0.83), though not in fed butterflies of the same age range (r = -0.02). However, repeatability of CO(2) production of fed butterflies increased sharply with age, rising to 0.82 for butterflies age 8-10 d. Although food uptake mass was repeatable (r = 0.52), feeding history explained little variation in CO(2) production. We conclude that for V. cardui and possibly for other insects of similar feeding habit, variation in metabolic rate between individuals is best represented by measurements of unfed individuals of the same age or of older fed individuals.

Visceral-locomotory pistoning in crawling caterpillars.

Animals with an open coelom do not fully constrain internal tissues, and changes in tissue or organ position during body movements cannot be readily discerned from outside of the body. This complicates modeling of soft-bodied locomotion, because it obscures potentially important changes in the center of mass as a result of internal tissue movements. We used phase-contrast synchrotron X-ray imaging and transmission light microscopy to directly visualize internal soft-tissue movements in freely crawling caterpillars. Here we report a novel visceral-locomotory piston in crawling Manduca sexta larvae, in which the gut slides forward in advance of surrounding tissues. The initiation of gut sliding is synchronous with the start of the terminal prolegs' swing phase, suggesting that the animal's center of mass advances forward during the midabdominal prolegs' stance phase and is therefore decoupled from visible translations of the body. Based on synchrotron X-ray data and transmission light microscopy results, we present evidence for a two-body mechanical system with a nonlinear elastic gut that changes size and translates between the anterior and posterior of the animal. The proposed two-body system--the container and the contained--is unlike any form of legged locomotion previously reported and represents a new feature in our emerging understanding of crawling.

The transient relationship between pressure and volume in the pediatric pulmonary system.

An accurate understanding of the relationship between pulmonary pressure and volume is required for modeling pulmonary mechanics in a variety of clinical applications. In this study the experimental techniques and mathematical formulations used to characterize viscoelastic materials are applied to characterize transient pulmonary compliance in juvenile swine. Fixed volumes of air were insufflated into 5 swine and held constant for 45 s while the transient decay in tracheal pressure was measured. An analytical model was developed using an optimization scheme that maximized the model fit to the experimental data over the entire time convolution. The initial injected volume was varied to assess the spatial and temporal linearity of the behavior. Model performance was assessed by comparing measured and predicted pressure during insufflations of erratic volume waveforms. It is concluded that the pulmonary impedance of healthy juveniles can be adequately described over a wide volume and frequency range using a relatively simple 5-parameter model that is linear both spatially and temporally.

The energetic costs of stereotyped behavior in the paper wasp, Polistes dominulus.

Polistes wasps engage in many behavioral interactions. Although there has been debate over the meaning of these interactions, these stereotypical behaviors can be used to determine a colony's linear dominance hierarchy. Due to the implicit relationship between behavioral and reproductive dominance, behavioral interactions are commonly used to distinguish the reproductively dominant alpha foundress from the beta foundress. It has been suggested that in order to maintain reproductive control, the alpha foundress is forced to remain at a physiologically constrained activity limit. This, in turn, may allow aggressive interactions to be used as determinants influencing reproductive partitioning between cooperating individuals. Energetic costs can place important limitations on behavior, but the energetic cost of the interactions has not previously been measured. To address this, we measured the CO(2) production of 19 non-nestmate pairs displaying interactive and noninteractive behavior. The rate of energy used during interaction behavior was positively associated with published rankings of aggression. However, our results indicate that interactions are not very energetically costly in Polistes, particularly when compared to the likely cost of foraging. These data suggest that maintaining reproductive dominance is not very energetically expensive for the dominant and that the dominant foundress expends energy at a lower rate than the subordinate foundress.

Dynamic properties of a locomotory muscle of the tobacco hornworm Manduca sexta during strain cycling and simulated natural crawling.

Caterpillars are soft-bodied terrestrial climbers that perform a wide variety of complex movements with several hundred muscles and a relatively small number of neurons. Control of movements is therefore expected to place unusual demands on the mechanical properties of the muscles. The muscles develop force slowly (1-6 s to peak) yet over a strain range extending from under 60% to more than 160% of resting length, with a length-tension relationship resembling that of supercontracting or cross-striated muscle. In passive and active sinusoidal strain cycling, muscles displayed viscoelastic qualities, with very low and stretch-velocity dependent resilience; there was a positive linear relationship between stretch velocity and the fraction of work dissipation attributable to passive muscle properties (20-80%). In linear stretches of unstimulated muscles at velocities bracketing those encountered in natural crawling, the rise in tension showed a distinct transition to a lower rate of increase, with transition tension dependent upon stretch velocity; peak force was exponentially related to stretch velocity. When stretching ceased, force decayed exponentially, with slower decay associated with lower stretch velocities; the decay time constant was exponentially related to stretch velocity. From the kinematics of caterpillars crawling horizontally we determined that the ventral interior lateral muscle (VIL) of the third abdominal segment (A3) is at or near resting length for most of the crawl cycle, with a fairly linear shortening by 25-30% and re-lengthening occupying about 45% of cycle duration. Synchronized kinematic and EMG recordings showed that during horizontal crawling A3 VIL is stimulated as the muscle shortens from about 95% to 75% of its resting length. We subjected in vitro VIL preparations to strain cycling and stimulus phase and duration similar to that of natural crawling. The resulting work loops were figure-eight shaped, with the muscle performing work during the shortest 45-65% of the strain cycle but dissipating work during the rest of the cycle. The muscle remained in the ascending limb of its length-tension relationship throughout the crawl cycle. Peak force occurred at the end of re-lengthening, nearly a full second after stimulation ceased, underscoring the importance of understanding passive muscle properties to explain caterpillar locomotion. Whether A3 VIL functions as an actuator at all during simulated natural strain cycling is highly sensitive to stimulus timing but far less so to stimulus duration. The muscle's elastomer-like properties appear to play a major role in its function.

Muscle performance in a soft-bodied terrestrial crawler: constitutive modelling of strain-rate dependency.

Experimental data on the passive mechanical properties of the ventral interior lateral muscle of the tobacco hornworm caterpillar, Manduca sexta, are reported. The stress-deformation response of the Manduca muscle is shown to be nonlinear pseudo-elastic, capable of large deformations and subject to stress softening during initial loading cycles. The muscle passive mechanical properties also depend on multiple time-dependent processes. In particular, we show new experimental data from cyclic loading tests of an unstimulated muscle with constant maximum stretch and different, constant engineering strain rates. Then, on the basis of these data a constitutive model is derived to reproduce the main characteristics of this behaviour. In formulating the constitutive model, we consider the muscle as a complex macromolecular structure with fibrous components at numerous size scales. The model uses a phenomenological approach to account for different mechanisms by which passive force changes during applied deformation and how the muscle properties recover after unloading.

Care of the acutely ill pediatric heart transplant recipient.

Young children may present to the emergency department after undergoing orthotopic heart transplantation. Emergency department care of pediatric heart transplant recipients with an acute illness is not clearly defined. To assist the emergency physician with treating these children, 2 cases are detailed to demonstrate the variation in outcome of young children presenting to the emergency department with acute illness months after their transplant. The cases typify the varied outcomes possible after emergency department presentation. After the cases, a review of the medical conditions common in transplant recipients precedes a description of management suggestions.

Energy and predation costs of firefly courtship signals.

Animal courtship signals include many highly conspicuous traits and behaviors, and it is generally assumed that such signals must balance the benefits of attracting mates against some fitness costs. However, few studies have assessed the multiple costs potentially incurred by any one courtship signal, so we have limited understanding of the relative importance of different costs. This study provides the first comprehensive assessment of signal costs for Photinus fireflies (Coleoptera: Lampyridae), using controlled experiments to measure both the energy and predation costs associated with their bioluminescent courtship signals. We measured energy required to generate bioluminescent flashes, using differential open-flow respirometry, and found that flash signaling results in only a nominal increase in energy expenditure above resting levels. These results suggest that the energy required to generate bioluminescent flashes represents a minor component of the total cost of firefly courtship. However, controlled field experiments revealed that visually oriented predators imposed major costs on firefly courtship signals, with higher signaling rates significantly increasing the likelihood of predation. Together with previous results demonstrating that female fireflies prefer more conspicuous courtship signals, these results support the importance of multiple-receiver communication networks in driving signal evolution.

Condition indices for conservation: new uses for evolving tools.

Biologists have developed a wide range of morphological, biochemical and physiological metrics to assess the health and, in particular, the energetic status of individual animals. These metrics originated to quantify aspects of human health, but have also proven useful to address questions in life history, ecology and resource management of game and commercial animals. We review the application of condition indices (CI) for conservation studies and focus on measures that quantify fat reserves, known to be critical for energetically challenging activities such as migration, reproduction and survival during periods of scarcity. Standard methods score fat content, or rely on a ratio of body mass rationalized by some measure of size, usually a linear dimension such as wing length or total body length. Higher numerical values of these indices are interpreted to mean an animal has greater energy reserves. Such CIs can provide predictive information about habitat quality and reproductive output, which in turn can help managers with conservation assessments and policies. We review the issues about the methods and metrics of measurement and describe the linkage of CIs to measures of body shape. Debates in the literature about the best statistical methods to use in computing and comparing CIs remain unresolved. Next, we comment on the diversity of methods used to measure body composition and the diversity of physiological models that compute body composition and CIs. The underlying physiological regulatory systems that govern the allocation of energy and nutrients among compartments and processes within the body are poorly understood, especially for field situations, and await basic data from additional laboratory studies and advanced measurement systems including telemetry. For now, standard physiological CIs can provide supporting evidence and mechanistic linkages for population studies that have traditionally been the focus of conservation biology. Physiologists can provide guidance for the field application of conditions indices with validation studies and development of new instruments.