Update on biphasic anaphylaxis

Rocuronium-Induced Anaphylaxis in the Perioperative Period: A Clinical Review

Rocuronium, a nondepolarizing neuromuscular blocking agent used for muscle relaxation especially during endotracheal intubation, can cause hypersensitivity reactions. This article provides an overview of anaphylactic reactions; risk factors; and the pathophysiology, presentation, diagnosis, treatment, and nursing implications associated with rocuronium-induced anaphylaxis. Life-threatening anaphylaxis can be immunoglobulin E-mediated or non-immunoglobulin E-mediated and usually occurs after the first dose. Anaphylaxis can present with hypotension and bronchospasm; cutaneal symptoms, such as erythema, may not be obvious. Diagnosis is initially presumptive and may require a transesophageal echocardiogram to rule out other causes of hypotension (eg, pulmonary embolus). Emergency treatment begins with epinephrine administration and fluid boluses; cardiac support devices may be needed. Definitive diagnosis requires early measurement of histamine and tryptase levels and skin testing after the patient recovers from the reaction. Perioperative nurses should be prepared to participate in emergency treatment of anaphylaxis and advocate for testing for a definitive diagnosis.

Biologics to treat anaphylaxis

PURPOSE OF REVIEW

The purpose of this literature review was to review the latest use of biologics in the management of anaphylaxis. The methodology was to highlight both the nonbiologic management of anaphylaxis and the biologic management and how they can be used in conjunction with each other.

RECENT FINDINGS

As the phenotypes and endotypes of anaphylaxis are better portrayed, it furthers our understanding of the mechanisms of anaphylaxis. New applications of existing biologics to the prevention of anaphylaxis are described.

SUMMARY

Anaphylaxis is a potentially life-threatening acute hypersensitivity reaction affecting up to 16.8% of the U.S. population. Acute management entails swift identification, removal of the causative agent, and the prevention of cardiovascular collapse, firstly with epinephrine. Adjunctive treatments such as antihistamines work to prevent anaphylaxis from recurring. Biologic management of anaphylaxis involves the use of large-molecule drugs such as monoclonal antibodies. Omalizumab, an IgG1 monoclonal antibody targeting unbound IgE, is the most prevalent and widely studied biologic in the prevention of anaphylaxis. Other monoclonal antibodies in development or approved for other indications, such as ligelizumab, quilizumab, MEDI4212, and dupilumab, may also have potential for preventing anaphylaxis through various mechanisms.

Anaphylaxis: Emergency Department Treatment

Anaphylaxis is a potentially life-threatening, multisystem allergic reaction that can cause airway, breathing, or circulatory compromise. Intramuscular epinephrine is the immediate treatment of all patients. Intravenous epinephrine should be used in patients in shock, either as a bolus or infusion, along with fluid resuscitation. Airway obstruction must be recognized, and early intubation may be necessary. For shock that is refractory to epinephrine, additional vasopressors may be needed. Disposition depends on patient presentation and response to treatment. Mandatory observation periods are not necessary, because biphasic reactions are difficult to predict and may occur outside of typical observation periods.

Overview of Allergy and Anaphylaxis

Allergic reactions and anaphylaxis occur on a severity continuum from mild and self-limited to potentially life-threatening or fatal reactions. Anaphylaxis is typically a multiorgan phenomenon involving a broad range of effector cells and mediators. Emergency department visits for anaphylaxis are increasing, especially among children. There is a broad differential diagnosis for anaphylaxis, and the diagnosis of anaphylaxis can be aided by the use of the National Institutes of Allergy and Infectious Disease/Food Allergy and Anaphylaxis Network clinical diagnostic criteria. Risk factors for severe anaphylaxis include older age, delayed epinephrine administration, and cardiopulmonary comorbidities.

The Utilization of Activated Charcoal in the Management of Anaphylaxis: A Case Series

Anaphylaxis is a sudden onset of systemic hypersensitivity caused by mast cell and basophil degranulation. Food, Hymenoptera venom, and drug allergy are among the leading causes of anaphylaxis, particularly in adults. We can consider anaphylaxis caused by swallowing food or medication as a form of poisoning. Because in anaphylaxis, just like in poisoning, an allergen entering the body poses a life-threatening risk. Therefore, the allergen should be removed from the digestive system immediately. However, the decontamination of the gastrointestinal tract is not routinely used to prevent further absorption of allergens from the intestine into the systemic circulation. Among the gastrointestinal decontamination methods is the use of activated charcoal. In this article, we present four patients who developed anaphylaxis due to drug and food intake and were administered oral activated charcoal after their primary treatment (on average, 15-45 minutes after the first presentation) was completed. The youngest of the patients was 22 years old, and the oldest was 40. No side effects, prolonged anaphylactic state, and biphasic reactions were observed in the follow-up of the patients. All patients were discharged after 48-72 hours of hospitalization. The routine approach to poisoning treatment includes patient stabilization, toxidrome recognition, antidote administration, and supportive care, as well as measures to enhance toxin elimination. In anaphylaxis caused by oral allergens, the substance that initiates the reaction can be compared to a kind of toxin. Eliminating the allergen and reducing its absorption could be achieved by administering activated charcoal. Activated charcoal should be considered adjunctive therapy in treating food and oral drug-induced anaphylaxis. This treatment, when administered in a timely manner, might prevent the development of biphasic reactions and the prolongation of the allergic process in anaphylaxis.

Canadian Anaphylaxis Network-Predicting Recurrence after Emergency Presentation for Allergic REaction (CAN-PREPARE): a prospective, cohort study protocol

INTRODUCTION

Anaphylaxis is a severe, potentially fatal multiorgan system manifestation of an allergic reaction. The highest incidence of anaphylaxis is in children and adolescents. Biphasic anaphylaxis (BA) is defined as the recurrence of allergic symptoms after resolution of an initial reaction. It has been reported to occur in 10%-20% of cases within 1-48 hours from the onset of the initial reaction. The dilemma for physicians is determining which patients with resolved anaphylaxis should be observed for BA and for how long. Guidelines for duration of postanaphylaxis monitoring vary, are based on limited evidence and can have unintended negative impacts on patient safety, quality of life and healthcare resources. The objectives of this study are to derive a prognostic model for BA and to develop a risk-scoring system that informs disposition decisions of children who present to emergency departments (ED) with anaphylaxis.

METHODS AND ANALYSIS

This prospective multicentre cohort study will enrol 1682 patients from seven paediatric EDs that are members of the Paediatric Emergency Research Canada network. We will enrol patients younger than 18 years of age with an allergic reaction meeting anaphylaxis diagnostic criteria. Trained ED research assistants will screen, obtain consent and prospectively collect study data. Research assistants will follow patients during their ED visit and ascertain, in conjunction with the medical team, if the patient develops BA. A standardised follow-up survey conducted following study enrolment will determine if a biphasic reaction occurred after ED disposition. Model development will conform to the broad principles of the PROGRESS (Prognosis Research Strategy) framework and reporting will follow the Transparent Reporting of a multivariable prediction model for Individual Prognosis or Diagnosis Statement.

ETHICS AND DISSEMINATION

Ethics approval has been received from all participating centres. Our dissemination plan focuses on informing clinicians, policy makers and parents of the results through publication in peer-reviewed journals and broadcasting on multiple media platforms.

TRIAL REGISTRATION NUMBER

NCT05135377.

Wilderness Medical Society Clinical Practice Guidelines on Anaphylaxis

The Wilderness Medical Society convened a panel to review the literature and develop evidence-based clinical practice guidelines on the treatment of anaphylaxis, with an emphasis on a field-based perspective. The review also included literature regarding the definition, epidemiology, clinical manifestations, and prevention of anaphylaxis. The increasing prevalence of food allergies in the United States raises concern for a corresponding rise in the incidence of anaphylaxis. Intramuscular epinephrine is the primary treatment for anaphylaxis and should be administered before adjunctive treatments such as antihistamines, corticosteroids, and inhaled β agonists. For outdoor schools and organizations, selecting a method to administer epinephrine in the field is based on considerations of cost, safety, and first responder training, as well as federal guidelines and state-specific laws.

Overview of Allergy and Anaphylaxis

Allergic reactions and anaphylaxis occur on a severity continuum from mild and self-limited to potentially life-threatening or fatal reactions. Anaphylaxis is typically a multiorgan phenomenon involving a broad range of effector cells and mediators. Emergency department visits for anaphylaxis are increasing, especially among children. There is a broad differential diagnosis for anaphylaxis, and the diagnosis of anaphylaxis can be aided by the use of the National Institutes of Allergy and Infectious Disease/Food Allergy and Anaphylaxis Network clinical diagnostic criteria. Risk factors for severe anaphylaxis include older age, delayed epinephrine administration, and cardiopulmonary comorbidities.

Anaphylaxis: Emergency Department Treatment

Anaphylaxis is a potentially life-threatening, multisystem allergic reaction that can cause airway, breathing, or circulatory compromise. Intramuscular epinephrine is the immediate treatment of all patients. Intravenous epinephrine should be used in patients in shock, either as a bolus or infusion, along with fluid resuscitation. Airway obstruction must be recognized, and early intubation may be necessary. For shock that is refractory to epinephrine, additional vasopressors may be needed. Disposition depends on patient presentation and response to treatment. Mandatory observation periods are not necessary, because biphasic reactions are difficult to predict and may occur outside of typical observation periods.

Peanut (Arachis hypogaea) Allergen Powder-dnfp: The First FDA-approved Oral Immunotherapy for Desensitization of Peanut Allergy in Children

Peanut (Arachis hypogaea) Allergen Powder-dnfp (Palforzia, Aimmune™ Therapeutics, Inc.; Brisbane, CA) is the first FDA-approved oral immunotherapy indicated for the mitigation of allergic reactions, including anaphylaxis, in patients with peanut allergy. It may be initiated in individuals 4 to 17 years of age and continued for maintenance in those 4 years of age and older. Initiation and dose titration require a stepwise approach and the supervision of a health care professional. Patients taking Peanut (Arachis hypogaea) Allergen Powder-dnfp should also follow a peanut-avoidant diet. In addition, patients should have an injectable epinephrine product in case of drug-related anaphylaxis. Commonly reported adverse reactions include gastrointestinal, respiratory, and dermatologic manifestations that are frequently associated with allergic reactions.

Factors influencing emergency department observation time following anaphylaxis: a systematic review

OBJECTIVE

Anaphylaxis is a condition that warrants an observation period after symptoms resolution to detect rare but life-threatening delayed complications. There is a need for evidence to identify patients who would benefit from prolonged observation time. The purpose of this review was to identify factors that may influence the need for longer observation in the emergency department.

METHODS

PubMed, Embase, EBM Review, and Cochrane Library were searched using controlled vocabulary and keywords to cover all relevant data. Titles, abstract, and full text were reviewed for inclusion and exclusion criteria. Data were extracted from the included articles regarding case definitions, prognosis, treatment and time factors, and recommended observation time. Factors linked to observation time or complications were tabulated and compared between studies.

RESULTS

The search retrieved 2443 citations of which 49 were included. Twenty-one were primary studies and were used to identify factors influencing observation time or complications. Biphasic anaphylaxis was the only adverse event that warranted prolonged observation. The five risk factors often associated with biphasic reactions were time to first epinephrine, history of anaphylaxis, symptom severity, number of epinephrine doses, and unknown trigger. Biphasic reactions happened mostly within the first 72 h with most severe reactions occurring earlier than the milder ones. Heterogeneity in the definition of biphasic anaphylaxis made comparisons challenging.

CONCLUSIONS

Observation time should be based on the provider's best estimation of the risk of biphasic anaphylaxis, although no single factor can predict their occurrence. The identified factors will allow the development of an early discharge screening tool.

Medicolegal Implications of Biphasic Anaphylaxis

ABSTRACT

Biphasic anaphylaxis is an uncommon IgE-mediated condition whose pathophysiological mechanisms, risk factors, and predictive signs are not properly understood. Fortunately, the lethality of biphasic anaphylaxis, although probably underestimated, is low. Preventive clinical measures for biphasic anaphylaxis are neither standardized nor commonly applied. Furthermore, there are no laboratory protocols or anaphylactic markers to help identify the onset of biphasic anaphylaxis in clinical settings. The aim of this review is to highlight the medicolegal difficulties facing coroners and forensic pathologists in terms of the diagnosis and assessment of harm for victims and survivors of biphasic anaphylaxis.

Critical Care Management of the Patient With Anaphylaxis: A Concise Definitive Review

OBJECTIVES

Anaphylaxis is a rapidly progressive life-threatening syndrome manifesting as pruritus, urticaria, angioedema, bronchospasm and shock. The goal of this synthetic review is to provide a practical, updated approach to the evaluation and management of this disorder and associated complications.

DATA SOURCES

A MEDLINE search was conducted with the MeSH of anaphylaxis, anaphylactic reaction, anaphylactic shock, refractory anaphylaxis and subheadings of diagnosis, classification, epidemiology, complications and pharmacology. The level of evidence supporting an intervention was evaluated based on the availability of randomized studies, expert opinion, case studies, reviews, practice parameters and other databases (including Cochrane).

STUDY SELECTION

Selected publications describing anaphylaxis, clinical trials, diagnosis, mechanisms, risk factors and management were retrieved (reviews, guidelines, clinical trials, case series) and their bibliographies were also reviewed to identify relevant publications.

DATA EXTRACTION

Data from the relevant publications were reviewed, summarized and the information synthesized.

DATA SYNTHESIS

This is a synthetic review and the data obtained from a literature review was utilized to describe current trends in the diagnosis and management of the patient with anaphylaxis with a special emphasis on newer evolving concepts of anaphylaxis endotypes and phenotypes, management of refractory anaphylaxis in the ICU setting and review of therapeutic options for the elderly patient, or the complicated patient with severe cardiorespiratory complications. Most of the recommendations come from practice parameters, case studies or expert opinions, with a dearth of randomized trials to support specific interventions.

CONCLUSION

Anaphylaxis is a rapidly progressive life-threatening disorder. The critical care physician needs to be familiar with the diagnosis, differential diagnosis, evaluation, and management of anaphylaxis. Skilled intervention in ICUs may be required for the patient with complicated, severe, or refractory anaphylaxis.

Community Use of Epinephrine for the Treatment of Anaphylaxis: A Review and Meta-Analysis

BACKGROUND

Community use of epinephrine for the treatment of anaphylaxis is low. Knowledge of rates of epinephrine use in the pre-hospital setting along with identification of barriers to its use will contribute to the development of policies and guidelines.

OBJECTIVES

A search was conducted on PubMed and Embase in April 2020. Our systematic review focused on 4 domains: (1) epinephrine use in the pre-hospital setting; (2) barriers to epinephrine use in the pre-hospital setting; (3) cost evaluation and cost-effectiveness of epinephrine use; and (4) programs and strategies to improve epinephrine use during anaphylaxis.

METHODS

Two meta-analyses with logit transformation were conducted to: (1) calculate the pooled estimate of the rate of epinephrine use in the pre-hospital setting among cases of anaphylaxis and (2) calculate the pooled estimate of the rate of biphasic reactions among all cases of anaphylaxis.

RESULTS

Epinephrine use in the pre-hospital setting was significantly higher for children compared with adults (20.98% [95% confidence interval (CI): 16.38%, 26.46%] vs 7.17% [95% CI: 2.71%, 17.63%], respectively, P = .0027). The pooled estimate of biphasic reactions among all anaphylaxis cases was 3.92% (95% CI: 2.88%, 5.32%). Our main findings indicate that pre-hospital use of epinephrine in anaphylaxis remains suboptimal. Major barriers to the use of epinephrine were identified as low prescription rates of epinephrine autoinjectors and lack of stock epinephrine in schools, which was determined to be cost-effective. Finally, in reviewing programs and strategies, numerous studies have engineered effective methods to promote adequate and timely use of epinephrine.

CONCLUSION

The main findings of our study demonstrated that across the globe, prompt epinephrine use in cases of anaphylaxis remains suboptimal. For practical recommendations, we would suggest considering stock epinephrine in schools and food courts to increase the use of epinephrine in the community. We recommend use of pamphlets in public areas (ie, malls, food courts, etc.) to assist in recognizing anaphylaxis and after that with prompt epinephrine administration, to avoid the rare risk of fatality in anaphylaxis cases.

PEMCRC anaphylaxis study protocol: a multicentre cohort study to derive and validate clinical decision models for the emergency department management of children with anaphylaxis

INTRODUCTION

There remain significant knowledge gaps about the management and outcomes of children with anaphylaxis. These gaps have led to practice variation regarding decisions to hospitalise children and length of observation periods following treatment with epinephrine. The objectives of this multicentre study are to (1) determine the prevalence of and risk factors for severe, persistent, refractory and biphasic anaphylaxis, as well as persistent and biphasic non-anaphylactic reactions; (2) derive and validate prediction models for emergency department (ED) discharge; and (3) determine data-driven lengths of ED and inpatient observation prior to discharge to home based on initial reaction severity.

METHODS AND ANALYSIS

The study is being conducted through the Pediatric Emergency Medicine Collaborative Research Committee (PEMCRC). Children 6 months to less than 18 years of age presenting to 30 participating EDs for anaphylaxis from October 2015 to December 2019 will be eligible. The primary outcomes for each objective are (1) severe, persistent, refractory or biphasic anaphylaxis, as well as persistent or biphasic non-anaphylactic reactions; (2) safe ED discharge, defined as no receipt of acute anaphylaxis medications or hypotension beyond 4 hours from first administered dose of epinephrine; and (3) time from first to last administered dose of epinephrine and vasopressor cessation. Analyses for each objective include (1) descriptive statistics to estimate prevalence and generalised estimating equations that will be used to investigate risk factors for anaphylaxis outcomes, (2) least absolute shrinkage and selection operator regression and binary recursive partitioning to derive and validate prediction models of children who may be candidates for safe ED discharge, and (3) Kaplan-Meier analyses to assess timing from first to last epinephrine doses and vasopressor cessation based on initial reaction severity.

ETHICS AND DISSEMINATION

All sites will obtain institutional review board approval; results will be published in peer-reviewed journals and disseminated via traditional and social media, blogs and online education platforms.

Quality of the Triage of Children With Anaphylaxis at the Emergency Department

OBJECTIVE

Early recognition of symptoms is essential in anaphylaxis management. The Canadian Paediatric Emergency Triage and Acuity Scale prioritizes anaphylaxis to level I or II (resuscitation or emergency). We analyzed the accuracy of pediatric anaphylaxis triage.

METHODS

This was a retrospective review of the triage charts (adaptation of the Canadian Paediatric Emergency Triage and Acuity Scale) of 137 children attended for anaphylaxis at our pediatric emergency department. Per triages' accuracy, charts were divided into TR1 (levels I-II) and TR2 (levels III-V), comparing demographics, initial triage level given by initial assessment (Paediatric Assessment Triangle), vital signs, observations recorded by the staff, and waiting times for physician.

RESULTS

Forty-six (33.3%) were triaged correctly (TR1 group), and 91 (66.7%) were not. Median ages were similar (TR1: 5 years [interquartile range, 13.1 years] vs TR2: 4.5 years [interquartile range, 14.5 years]; P = 0.837). Initial triage level 5 was given by Paediatric Assessment Triangle to 69.5% of TR1 and 83% of TR2 cases (P = 0.001; likelihood ratio for TR2: 1.985 [95% confidence interval, 1.11-3.49]). Vital signs were normal in 71.7% of TR1 and 94.5% of TR2 patients (P < 0.001; likelihood ratio for TR2: 2.602 [95% confidence interval, 1.22-5.52]). Symptoms suggestive of anaphylaxis (mention of 2 different organs) were recorded in 45.6% of TR1 and 48.3% of TR2 charts (P = 0.08). Median waiting times were 3 minutes (interquartile range, 26 minutes) and 11 minutes (interquartile range, 111 minutes) for TR1 and TR2, respectively (P = 0.001).

CONCLUSIONS

Current triage, based on severity perception, missed most of the cases. Anaphylaxis-defining symptoms were overlooked. Inaccurate triage delayed medical attention. Improving measures, such as emphasizing symptom recognition and defining anaphylaxis risk discriminators, is mandatory to improve their identification.

Persistent, refractory, and biphasic anaphylaxis: A multidisciplinary Delphi study

BACKGROUND

The use of inconsistent definitions for anaphylaxis outcomes limits our understanding of the natural history and epidemiology of anaphylaxis, hindering clinical practice and research efforts.

OBJECTIVE

Our aim was to develop consensus definitions for clinically relevant anaphylaxis outcomes by utilizing a multidisciplinary group of clinical and research experts in anaphylaxis.

METHODS

Using Delphi methodology, we developed agenda topics and drafted questions to review during monthly conference calls. Through online surveys, a 19-member panel consisting of experts in allergy and/or immunology and emergency medicine rated their level of agreement with the appropriateness of statements on a scale of 1 to 9. A median value of 1.0 to 3.4 was considered inappropriate, a median value of 3.5 to 6.9 was considered uncertain, and a median value of 7.0 to 9.0 was considered appropriate. A disagreement index was then calculated, with values less than 1.0 categorized as "consensus reached." If consensus was not reached after the initial survey, subsequent surveys incorporating the aggregate de-identified responses from prior surveys were sent to panel members. This process was repeated until consensus was reached or 4 survey rounds had been completed, after which the question was categorized as "no consensus reached."

RESULTS

The panel developed outcome definitions for persistent, refractory, and biphasic anaphylaxis, as well as for persistent and biphasic nonanaphylactic reactions. There was also consensus among panel members regarding the need to develop an anaphylaxis severity grading system.

CONCLUSION

Dissemination and application of these definitions in clinical care and research will help standardize the terminology used to describe anaphylaxis outcomes and serve as the foundation for future research, including research aimed at development of an anaphylaxis severity grading system.

Simulation of Health and Economic Benefits of Extended Observation of Resolved Anaphylaxis

IMPORTANCE

Biphasic anaphylaxis may occur in up to 20% of patients with anaphylaxis; however, the optimal observation time of patients with resolved anaphylaxis is unknown.

OBJECTIVE

To characterize the cost-effectiveness of short vs prolonged medical observation times after resolved anaphylaxis.

DESIGN, SETTING, AND PARTICIPANTS

An economic evaluation was performed of computer-simulated adult patients observed in outpatient allergy clinics and emergency departments, with rates of biphasic anaphylaxis derived from a 2019 meta-analysis.

EXPOSURES

Computer-simulated patients (10 000 per strategy) were randomized to undergo 1 hour of medical observation (associated with 95% negative predictive value of biphasic anaphylaxis) or 6 or more hours of observation (associated with a 97.3% negative predictive value of biphasic anaphylaxis).

MAIN OUTCOMES AND MEASURES

Cost-effectiveness of 6- to 24-hour medical observation of resolved anaphylaxis evaluated at willingness-to-pay thresholds of $10 000 per case of biphasic anaphylaxis observed and $10 million per death prevented, assuming that observation is associated with a 10- to 1000-fold reduction in the risk of death due to biphasic anaphylaxis.

RESULTS

Biphasic anaphylaxis occurred after hospital discharge in 365 patients observed for 1 hour and in 213 patients undergoing prolonged observation. From a health care sector perspective, with medical observation costs of $286.92 per hour, the incremental cost of extended medical observation of resolved anaphylaxis (1 hour vs 6 hours) was $62 374 per case of biphasic anaphylaxis identified ($68 411 from the societal perspective). In Monte Carlo simulations, with hourly costs ranging from $100 to $500 and extended observation ranging from 6 to 24 hours (health care sector perspective), the mean (SD) costs were $295.36 ($81.22) for 1 hour of observation vs $3540.42 ($1626.67) for extended observation. The incremental cost-effectiveness ratio was $213 439 per biphasic anaphylaxis observed ($230 202 from the societal perspective). A 6-hour observation could be cost-effective if the risk of biphasic anaphylaxis after 1-hour observation of resolved anaphylaxis was 17% or if hourly observation costs were less than $46 in the base case. Cost-effectiveness could also be achieved (willingness-to-pay of $10 million per death prevented, health care sector perspective) when a baseline fatality rate of 0.33% per biphasic anaphylactic event was assumed, with a no greater than 24% relative risk of fatality associated with 6-hour observation.

CONCLUSIONS AND RELEVANCE

This study indicates that prolonged medical observation (6-24 hours) for resolved anaphylaxis may not be cost-effective for patients at low risk for biphasic anaphylaxis; however, in particular clinical circumstances of low observation costs, high postdischarge risk of biphasic anaphylaxis, or large incremental fatality risk reduction associated with extended observation, longer medical observation can be justified.

Identification of children with anaphylaxis at low risk of receiving acute inpatient therapies

OBJECTIVE

Opportunity exists to reduce unnecessary hospitalizations for children with anaphylaxis given wide variation in admission rates across U.S. emergency departments (EDs). We sought to identify children hospitalized with anaphylaxis at low risk of receiving epinephrine and other acute inpatient therapies, as these patients may be candidates for ED discharge rather than inpatient hospitalization.

METHODS

We conducted a single-center retrospective cohort study of children 1-21 years of age hospitalized with anaphylaxis from 2009 to 2016. Acute inpatient therapies included intramuscular (IM) or racemic epinephrine, bronchodilators, fluid boluses, vasopressors, non-invasive ventilation, or intubation. We derived age-specific (pre-verbal [<36 months] vs. verbal [≥ 36 months]) prediction rules using recursive partitioning to identify children at low risk of receiving acute inpatient therapies.

RESULTS

During the study period 665 children were hospitalized for anaphylaxis, of whom 108 (16.2%) received acute inpatient therapies. The prediction rule for patients < 36 months (no wheezing, no cardiac involvement [hypotension or wide pulse pressure]) had a sensitivity of 90.5% (CI 69.6-98.8%) and a negative predictive value of 98.3% (CI 94.1-99.8%) for identifying children at low risk of receipt of acute inpatient therapies during hospitalization. For children ≥ 36 months, the prediction rule (no wheezing, no cardiac involvement, presence of gastrointestinal symptoms) had a sensitivity of 90.8% (CI 82.7-96.0%) and a negative predictive value of 92.4% (CI 85.6-96.7%).

CONCLUSIONS

We derived age specific prediction rules for children hospitalized with anaphylaxis at low risk of receiving epinephrine and other acute inpatient therapies. These children may be candidates for ED discharge rather than inpatient hospitalization.

Anaphylaxis

Anaphylaxis is an acute, potentially fatal systemic allergic reaction with varied mechanisms and clinical presentations. Although prompt recognition and treatment of anaphylaxis are imperative, both patients and healthcare professionals often fail to recognize and diagnose early signs and symptoms of the condition. Clinical manifestations vary widely; however, the most common signs are cutaneous symptoms, including urticaria, angioedema, erythema and pruritus. Immediate intramuscular administration of epinephrine into the anterolateral thigh is first-line therapy, even if the diagnosis is uncertain. The mainstays of long-term management include specialist assessment, avoidance measures, and the provision of an epinephrine auto-injector and an individualized anaphylaxis action plan. This article provides an overview of the causes, clinical features, diagnosis and acute and long-term management of this serious allergic reaction.

Biphasic anaphylaxis: A review of the literature and implications for emergency management

BACKGROUND

The biphasic reaction is a feared complication of anaphylaxis management in the emergency department (ED). The traditional recommended ED observation time is 4-6 h after complete resolution of symptoms for every anaphylaxis patient. However, there has been great controversy regarding whether this standard of care is evidence-based.

METHODS

Articles were selected using a PubMed, MEDLINE search for the keywords "biphasic anaphylaxis", yielding 155 articles. Articles were filtered by English language, and the keyword biphasic in the title. Case reports and case series were excluded, narrowing to 33 articles. Then, articles were filtered by relevance to the ED setting, and studies conducted in outpatient clinic settings were excluded, narrowing the search to 16 articles. All remaining articles were reviewed and findings were discussed.

RESULTS

The reported mean time to onset between the resolution of initial anaphylaxis and biphasic reaction ranges widely by study from 1 to 72 h with the majority of studies reporting the mean time to onset >8 h. A delay between anaphylaxis symptom onset and administration of epinephrine of 60-190 min was reported to correlate with biphasic anaphylaxis in three studies. Anaphylaxis requiring >1 dose of epinephrine to achieve symptom resolution was also reported to correlate with biphasic reactions in two studies. No definitive conclusions about the role of corticosteroids in preventing biphasic reactions can be made at this time however; a couple small studies have shown that they may decrease the incidence of biphasic reactions. Additional risk factors correlated with biphasic reaction vary widely between studies and the generalizability of these risk factors is questionable.

CONCLUSIONS

There is a need for further research to identify true risk factors associated with biphasic anaphylaxis and to clearly define the role of corticosteroids in biphasic reactions. However, given the low incidence and rare mortality of biphasic reactions, patients who receive epinephrine within one hour of symptom onset and who respond to epinephrine with rapid and complete symptom resolution can probably be discharged from the ED with careful return precautions and education without the need for prolonged observation.

Predictors of epinephrine dispensing and allergy follow-up after emergency department visit for anaphylaxis

BACKGROUND

National guidelines recommend that patients with anaphylaxis be prescribed an epinephrine auto-injector (EAI) and referred to an allergy/immunology (A/I) specialist.

OBJECTIVE

To evaluate guideline concordance and identify predictors of EAI dispensing and A/I follow-up in patients with anaphylaxis treated in the emergency department (ED).

METHODS

We identified patients seen in the ED for anaphylaxis from 2010 through 2014 from an administrative claims database using an expanded International Classification of Diseases, Ninth Revision, Clinical Modification diagnosis code algorithm.

RESULTS

Of 7,790 patients identified, 46.5% had an EAI dispensed and 28.8% had A/I follow-up within 1 year after discharge. On multivariable analysis, those 65 years or older (odds ratio [OR] 0.35, 95% confidence interval [CI] 0.30-0.41) and with a medication trigger (OR 0.24, 95% CI 0.21-0.28) had a lower likelihood of EAI dispensing. Those younger than 5 years (OR 2.67, 95% CI 2.15-3.32) and with food (OR 1.40, 95% CI 1.24-1.59) or venom (OR 4.48, 95% CI 3.51-5.72) triggers had a higher likelihood of EAI dispensing. Similarly, for A/I follow-up, the likelihood was lower for age 65 years or older (OR 0.46, 95% CI 0.39-0.54) and medication trigger (OR 0.66, 95% CI 0.56-0.78) and higher for age younger than 5 years (OR 3.15, 95% CI 2.63-3.77) and food trigger (OR 1.39, 95% CI 1.22-1.58).

CONCLUSION

Overall, 46.5% of patients with anaphylaxis in the ED had EAI dispensing and 28.8% had A/I follow-up. Patient age and triggers were associated with likelihood of EAI dispensing and A/I follow-up. Post-ED visit anaphylaxis management can be improved, with the potential to decrease future morbidity and mortality risk.

Anaphylaxis

Anaphylaxis is a systemic, life-threatening disorder triggered by mediators released by mast cells and basophils activated via allergic (IgE-mediated) or nonallergic (non-IgE-mediated) mechanisms. It is a rapidly evolving, multisystem process involving the integumentary, pulmonary, gastrointestinal, and cardiovascular systems. Anaphylaxis and angioedema are serious disorders that can lead to fatal airway obstruction and culminate in cardiorespiratory arrest, resulting in hypoxemia and/or shock. Often, these disorders can be appropriately managed in an outpatient setting; however, these conditions can be severe enough to warrant evaluation of the patient in the ED and in some cases, hospitalization, and management in an ICU. Reports suggest that underdiagnosis and undertreatment of anaphylaxis are common. Several new syndromes have been described recently including bird-egg, pork-cat, delayed allergy to mammalian meat and a diverse group of mast cell activation disorders. Conditions such as postural orthostatic tachycardia syndrome, carcinoid syndrome, Munchausen stridor, and factitious anaphylaxis can present similarly and need to be included in the differential diagnosis. Anaphylaxis is a clinical diagnosis, but plasma tryptase and urinary histamine levels are often elevated, allowing diagnostic confirmation; however, diagnostic testing should not delay treatment as results may not be immediately available. The sine qua non of treatment is avoidance of any known triggers and epinephrine, which should never be delayed if this disorder is suspected. Secondary treatments include fluids, bronchodilators, antihistamines, and glucocorticoids. Patients with cardiopulmonary arrest or airway or vascular compromise require mechanical ventilation, vasopressors, and other advanced life support in the ICU.

The pathophysiology of anaphylaxis

Anaphylaxis is a severe systemic hypersensitivity reaction that is rapid in onset; characterized by life-threatening airway, breathing, and/or circulatory problems; and usually associated with skin and mucosal changes. Because it can be triggered in some persons by minute amounts of antigen (eg, certain foods or single insect stings), anaphylaxis can be considered the most aberrant example of an imbalance between the cost and benefit of an immune response. This review will describe current understanding of the immunopathogenesis and pathophysiology of anaphylaxis, focusing on the roles of IgE and IgG antibodies, immune effector cells, and mediators thought to contribute to examples of the disorder. Evidence from studies of anaphylaxis in human subjects will be discussed, as well as insights gained from analyses of animal models, including mice genetically deficient in the antibodies, antibody receptors, effector cells, or mediators implicated in anaphylaxis and mice that have been "humanized" for some of these elements. We also review possible host factors that might influence the occurrence or severity of anaphylaxis. Finally, we will speculate about anaphylaxis from an evolutionary perspective and argue that, in the context of severe envenomation by arthropods or reptiles, anaphylaxis might even provide a survival advantage.

Risk Factors for Severe Reactions during Double-Blind Placebo-Controlled Food Challenges

BACKGROUND

Severe anaphylactic symptoms can occur during oral food challenges (OFCs). Thus, high-risk patients (e.g., patients with a history of anaphylaxis or high antigen-specific immunoglobulin E [IgE] levels) must carefully undergo OFCs in hospitals. We attempted to identify the risk factors for severe symptoms during OFC testing among high-risk patients.

METHODS

We retrospectively evaluated patients' characteristics and severe symptoms that were experienced during a double-blind placebo-controlled food challenge test performed before the patients underwent oral immunotherapy between June 2008 and June 2012. Patients were ≥5 years old and had an anaphylactic history or antigen-specific IgE (>30 kUA/L). Severe symptoms were defined using the grading of the Japanese Anaphylaxis Guidelines, which are modified from the European Academy of Allergology and Clinical Immunology Guidelines.

RESULTS

We evaluated 393 cases with positive test results, including 98 cases with severe symptoms. The most frequent severe symptoms were respiratory (77%), gastrointestinal (28%), cardiovascular (27%), and neurological (13%) symptoms. Multivariate analysis revealed that the significant factors for a severe reaction were a history of anaphylaxis to the causative food (adjusted odds ratio [OR]: 2.147, p = 0.003), older age (per 1 year increase, adjusted OR: 1.102, p = 0.044), and an egg OFC (adjusted OR: 0.433, p = 0.003).

CONCLUSIONS

The risk factors for a severe reaction to OFCs were a history of an anaphylactic reaction and older age. An egg OFC was associated with low risk of severe symptoms during OFC. Therefore, OFCs for patients with these risk factors should only be performed under specialist supervision with access to rapid treatment and full resuscitation equipment.