Risk assessment in anaphylaxis: current and future approaches

[Acetaminophene-induced hypotension in intensive care unit: a prospective study]

OBJECTIVES

The aim of this study was to evaluate the incidence of paracetamol-induced hypotension in intensive care unit (ICU). The secondary end-point was the description of pathophysiologic phenomenon during this hypotension and risk factors.

STUDY DESIGN

An observational study in three ICU of a French teaching hospital.

PATIENTS AND METHODS

All consecutives patients whom benefit from intravenous paracetamol administration were included in the study. When a 20% droop in arterial blood pressure occurred, plasma samples were obtained and tryptases were measured at 6 and 48 hours. Clinical, biological characteristics and paracetamol administration duration were prospectively monitored.

RESULTS

During a 2-months period, 127 ICU patients were included in the study with 1507 paracetamol administration. Twenty droops in arterial blood pressure were recorded in ICU. The incidence rate was 1.33%. Administration duration was 32+/-9 min. No respiratory nor cutaneous manifestations occurred during hypotensions. A specific treatment was administrated in half of the patients. Hypotension incidence was higher (3.9%) in patients with brain injury. Eighty percent of patients with hypotension have a severe sepsis or a septic shock.

CONCLUSION

In this cohort of ICU patients, hypotension incidence was higher than reported in drug legal mentions. Immunoallergic phenomenon was excluded. Brain injury and sepsis seems to be risk factors.

New insights into the roles for basophils in acute and chronic allergy

Basophils represent less than 1% of peripheral blood leukocytes. They are often recruited to the site of allergic inflammation, albeit in small numbers. However, it remained uncertain whether basophils play any significant role in allergic reactions or act as minor and redundant 'circulating mast cells'. We have recently demonstrated that basophils play critical roles in systemic anaphylaxis and chronic allergic inflammation, distinctively from mast cells. Basophils are one of the major players in the IgG- but not IgE-mediated systemic anaphylaxis, in contrast to mast cells. In response to the allergen-IgG immune complexes, basophils release the platelet-activating factor rather than histamine as the major chemical mediator to induce the systemic anaphylaxis. The depletion of basophils protects mice from death due to anaphylactic shock. Basophils also play a crucial role in the development of the IgE-mediated chronic allergic inflammation with massive eosinophil infiltration in the skin, independently of T cells and mast cells, even though basophils account for only approximately 2% of the infiltrates. The basophil depletion shows a therapeutic effect on on-going allergic inflammation. Accumulating evidence suggests that basophils function as initiators rather than effectors of the chronic allergic inflammation. Thus, basophils and their products seem to be promising therapeutic targets for allergic disorders.

Accidental allergic reactions in children allergic to cow's milk proteins

BACKGROUND

Cow's milk is the main cause of food allergy in children. Patients allergic to food frequently experience accidental exposure. There are few studies analyzing this problem, most of them concerning peanut allergy.

OBJECTIVE

We sought to calculate the frequency of accidental exposure reactions in children allergic to cow's milk during a 12-month period, to analyze the clinical characteristics and circumstances surrounding the reactions, and to identify risk factors for severe reactions.

METHODS

Eighty-eight children allergic to cow's milk (44 boys; median age, 32.5 months) were included in the study. A systematized questionnaire about accidental exposure was used. Reactions were classified as mild, moderate, and severe. Cow's milk- and casein-specific IgE antibody titers were determined.

RESULTS

Thirty-five (40%) children had 53 reactions in the previous year (53% mild, 32% moderate, and 15% severe). Most reactions took place at home (47%) under daily life circumstances (85%). Specific IgE levels to cow's milk were higher in children with severe reactions than in those with moderate (median, 37.70 vs 7.71 KUA/L; P = .04) or mild (3.37 KUA/L; P = .04) reactions. The frequency of severe reactions was 10-fold higher in asthmatic children (odds ratio, 10.2; 95% CI, 1.13-91.54).

CONCLUSIONS

Reactions to accidental exposure are frequent in children with cow's milk allergy. The proportion of severe reactions was 15%. The risk factors for such reactions included very high levels of specific IgE to cow's milk and casein and asthma.

Adrenaline for the treatment of anaphylaxis: cochrane systematic review

BACKGROUND

Anaphylaxis is a serious allergic reaction that is rapid in onset and may cause death. Adrenaline is recommended as the initial treatment of choice for anaphylaxis.

OBJECTIVES

To assess the benefits and harms of adrenaline in the treatment of anaphylaxis.

METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2007, Issue 1), MEDLINE (1966 to March 2007), EMBASE (1966 to March 2007), CINAHL (1982 to March 2007), BIOSIS (to March 2007), ISI Web of Knowledge (to March 2007) and LILACS (to March 2007). We also searched websites listing ongoing trials: http://www.clinicaltrials.gov/, http://www.controlledtrials.com and http://www.actr.org.au/ and contacted pharmaceutical companies and international experts in anaphylaxis in an attempt to locate unpublished material. Randomized and quasi-randomized controlled trials comparing adrenaline with no intervention, placebo or other adrenergic agonists were eligible for inclusion. Two authors independently assessed articles for inclusion.

RESULTS

We found no studies that satisfied the inclusion criteria.

CONCLUSIONS

On the basis of this review, we are unable to make any new recommendations on the use of adrenaline for the treatment of anaphylaxis. In the absence of appropriate trials, we recommend, albeit on the basis of less than optimal evidence, that adrenaline administration by intramuscular injection should still be regarded as first-line treatment for the management of anaphylaxis.

Newly discovered roles for basophils: a neglected minority gains new respect

Basophils are the least common type of granulocyte and they account for less than 1% of peripheral blood leukocytes. Because of this minority status and a phenotype that is similar to mast cells, basophils have often been neglected in immunological studies or considered to have minor, redundant roles in immune responses in vivo. However, recent studies have now defined previously unrecognized roles for basophils in both immune regulation and allergic responses, and have shown that basophils and mast cells have distinct roles in immune responses.

Hyperleukotrieneuria in patients with allergic and inflammatory disease

Cysteinyl leukotrienes (CysLTs: leukotrienes C(4), D(4), and E(4)) have long been implicated in the pathogenesis of asthma and several allergic diseases. LTE(4) has been identified as a major metabolite of LTC(4), and urinary LTE(4) (U-LTE(4)) is considered as the most reliable analytic parameter for monitoring the endogenous synthesis of CysLTs. From recent studies on the U-LTE(4) associated with adult stable asthma we identified four factors for hyperleukotrieneuria, namely, aspirin intolerance, eosinophilic nasal polyposis (ENP), vasculitis, and severe asthma. In ENP, there is prominent infiltration of eosinophils in the sinus and polyp tissues, which is linked to adult asthma and aspirin sensitivity, and ENP is the most important factor for the overproduction of CysLTs in asthmatics. We also demonstrated that anaphylaxis and eosinophilic pneumonia (EP) are associated with a marked increase in the U-LTE(4) concentration. Under these disease conditions, U-LTE(4) may be one of the candidate biomarkers. Moreover, the changes in U-LTE(4) concentrations may provide valuable information concerning therapeutic targets.

Anaphylaxis in referred pediatric patients: demographic and clinical features, triggers, and therapeutic approach

Anaphylaxis remains under-diagnosed and under-treated. A better knowledge of patterns and triggers of anaphylaxis might contribute to a better management. In this study we evaluated the demographic and clinical features of anaphylaxis in pediatric patients, as well as its triggers and therapeutic approach. From May 1st 2004 until April 30th 2006 we prospectively collected data on all patients referred for investigation of anaphylaxis to the pediatric department of the University Hospital Gasthuisberg Leuven and to two private pediatric practices. Data were stored in a MYSQL database by use of an online encrypted web form. Sixty-four cases of anaphylaxis occurred in 48 children, aged 6 months to 14.8 years. Twenty-seven episodes (42.2%) occurred at home. The symptoms were dermatologic in 62 (96.9%) episodes, respiratory in 57 (89.1%), gastrointestinal in 19 (29.7%), cardiovascular in 14 (21.8%), and neurological or behavioural in 19 (29.7%). Antihistamines were administered in 41/57 (71.9%) cases, corticosteroids in 26/57 (45.6%), beta-2-mimetics in 14/57 (24.6%), and adrenaline in 11/57 (19.3%). Out of nine cases where Epipen was available at the moment of anaphylaxis, it was administered in one case only. Food was the cause of anaphylaxis in 42/55 (76.4%) cases with identified trigger, while medication, insect stings, latex, and birch pollen triggered 5 (9.1%), 4 (7.3%), 3 (5.5%), and 1 (1.8%) case(s), respectively. Allergy to the trigger was known prior to anaphylaxis in 19/55 (34.5%) cases. In conclusion, anaphylaxis in pediatric patients generally presents with dermatologic and respiratory symptoms, while in 1/5 episodes cardiovascular symptoms occur. Food is by far the most frequent trigger. Allergy to the trigger is known in 1/3 cases only. Anaphylaxis is under-treated, even when appropriate medication is available.

Adrenaline (epinephrine) for the treatment of anaphylaxis with and without shock

BACKGROUND

Anaphylaxis is a serious hypersensitivity reaction that is rapid in onset and may cause death. Adrenaline is recommended as the initial treatment of choice for anaphylaxis.

OBJECTIVES

To assess the benefits and harms of adrenaline (epinephrine) in the treatment of anaphylaxis.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2007, Issue 1), MEDLINE (1966 to March 2007), EMBASE (1966 to March 2007), CINAHL (1982 to March 2007), BIOSIS (to March 2007), ISI Web of Knowledge (to March 2007) and LILACS (to March 2007). We also searched websites listing ongoing trials: http://clinicaltrials.gov/, http://www.controlledtrials.com and http://www.actr.org.au/; and contacted pharmaceutical companies and international experts in anaphylaxis in an attempt to locate unpublished material.

SELECTION CRITERIA

Randomized and quasi-randomized controlled trials comparing adrenaline with no intervention, placebo or other adrenergic agonists were eligible for inclusion.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed articles for inclusion.

MAIN RESULTS

We found no studies that satisfied the inclusion criteria.

AUTHORS' CONCLUSIONS

Based on this review, we are unable to make any new recommendations on the use of adrenaline for the treatment of anaphylaxis. Although there is a need for randomized, double-blind, placebo-controlled clinical trials of high methodological quality in order to define the true extent of benefits from the administration of adrenaline in anaphylaxis, such trials are unlikely to be performed in individuals with anaphylaxis. Indeed, they might be unethical because prompt treatment with adrenaline is deemed to be critically important for survival in anaphylaxis. Also, such studies would be difficult to conduct because anaphylactic episodes usually occur without warning, often in a non-medical setting, and differ in severity both among individuals and from one episode to another in the same individual. Consequently, obtaining baseline measurements and frequent timed measurements might be difficult, or impossible, to obtain. In the absence of appropriate trials, we recommend, albeit on the basis of less than optimal evidence, that adrenaline administration by intramuscular (i.m.) injection should still be regarded as first-line treatment for the management of anaphylaxis.

Food allergy in adults: an over- or underrated problem?

BACKGROUND

10% to 20% of the population sees itself as suffering from food allergy, yet genuine, immune-mediated food allergy is suspected by patients and their physicians far more often than it is actually shown to be present. The unfounded suspicion of an IgE-mediated food allergy can substantially impair a patient's quality of life through needless dietary restriction and the accompanying anxiety. On the other hand, an IgE-mediated food allergy that has gone undiagnosed or that has not been taken seriously can manifest suddenly with anaphylaxis, which may be life-threatening. The present study, carried out on a large cohort of patients, underscores the importance of differentiating IgE-mediated food allergy from other, nonallergic types of food reaction.

METHODS

419 patients that had been referred to our outpatient allergy clinic for suspected food allergies underwent a standardized allergological diagnostic evaluation, including thorough allergologic history-taking, IgE serology, and challenge tests when indicated.

RESULTS

214 patients (51.1%) were found to have an IgE-mediated food allergy. Almost half of these patients (24.3% of the overall group) had previously experienced food-induced anaphylaxis. In 205 patients (48.9%), however, an IgE-mediated food allergy was ruled out as far as possible.

CONCLUSION

Only a comprehensive allergological evaluation performed by an experienced allergologist in accordance with current guidelines can protect patients from the negative consequences of excessive concern about a nonexistent food allergy (e.g., needless dietary restriction) or, on the other hand, the negative consequences of inadequate attention to a genuine food allergy (anaphylaxis). A proper evaluation consists of detailed allergologic history-taking, skin tests, and challenge tests when indicated.

Allergy and the cardiovascular system

The most dangerous and life-threatening manifestation of allergic diseases is anaphylaxis, a condition in which the cardiovascular system is responsible for the majority of clinical symptoms and for potentially fatal outcome. The heart is both a source and a target of chemical mediators released during allergic reactions. Mast cells are abundant in the human heart, where they are located predominantly around the adventitia of large coronary arteries and in close contact with the small intramural vessels. Cardiac mast cells can be activated by a variety of stimuli including allergens, complement factors, general anesthetics and muscle relaxants. Mediators released from immunologically activated human heart mast cells strongly influence ventricular function, cardiac rhythm and coronary artery tone. Histamine, cysteinyl leukotrienes and platelet-activating factor (PAF) exert negative inotropic effects and induce myocardial depression that contribute significantly to the pathogenesis of anaphylactic shock. Moreover, cardiac mast cells release chymase and renin that activates the angiotensin system locally, which further induces arteriolar vasoconstriction. The number and density of cardiac mast cells is increased in patients with ischaemic heart disease and dilated cardiomyopathies. This observation may help explain why these conditions are major risk factors for fatal anaphylaxis. A better understanding of the mechanisms involved in cardiac mast cell activation may lead to an improvement in prevention and treatment of systemic anaphylaxis.

Exercise-induced hypersensitivity syndromes in recreational and competitive athletes: a PRACTALL consensus report (what the general practitioner should know about sports and allergy)

Exercise-induced (EI) hypersensitivity disorders are significant problems for both recreational and competitive athletes. These include EI-asthma, EI-bronchoconstriction, EI-rhinitis, EI-anaphylaxis and EI-urticaria. A group of experts from the European Academy of Allergology and Clinical Immunology and the American Academy of Allergy Asthma and Immunology met to discuss the pathogenesis of these disorders and how to diagnose and treat them, and then to develop a consensus report. Key words (exercise with asthma, bronchoconstriction, rhinitis, urticaria or anaphylaxis) were used to search Medline, the Cochrane database and related websites through February 2008 to obtain pertinent information which, along with personal reference databases and institutional experience with these disorders, were used to develop this report. The goal is to provide physicians with guidance in the diagnosis, understanding and management of EI-hypersensitivity disorders to enable their patients to safely return to exercise-related activities.

New visions for anaphylaxis: an iPAC summary and future trends

Anaphylaxis is an increasing emergency in Western countries, especially in children. In the last decade, efforts have been attempted to widely understand anaphylaxis from several angles but at present, there are still numerous issues to be clarified and tackled for its earlier identification. The discrepancies in the operational definitions and diagnostic criteria of anaphylaxis represent one of the most controversial issues in casting light upon its epidemiology. Furthermore, the lack of reliable markers of the disease hampers its diagnosis. Further basic and clinical research is urgently needed to confirm the recent promising results derived from studies on animal models, and to clarify the key role of selected mediators and markers in the different steps of the reaction, in its severity and in the recurrences. The underuse of adrenaline is another important issue, as available data demonstrate physicians' preference for steroids and anti-histamines despite the current lack of evidence of their effectiveness. In the near future, the management of anaphylaxis will be strongly influenced by the development of a stepwise approach, as well as by the creation of a system improving transmission of good quality data between the emergency room, the allergist and the family doctor. This process will certainly be enhanced by the establishment of a network of Centres of Excellence collaborating for high quality research and care and involved in the dissemination of new knowledge at a primary care level. This review will seek to briefly overview our current knowledge and highlight the key questions that need to be addressed in the next decade to improve clinical care to children and will focus on the epidemiology of anaphylaxis, the identification of individuals at risk of anaphylaxis, the special issues related to infants, community management of children at risk of anaphylaxis and school related issues.

Clinical immunology review series: an approach to the patient with anaphylaxis

Anaphylaxis is a severe, life-threatening, generalized or systemic hypersensitivity reaction. While there is agreement as to this definition of anaphylaxis, the clinical presentation is often variable and it is not uncommon for there to be debate after the event as to whether anaphylaxis had actually occurred. The management of anaphylaxis falls into two distinct phases: (1) emergency treatment and resuscitation of a patient with acute anaphylaxis and (2) the search for a cause for the event and the formulation of a plan to prevent and treat possible further episodes of anaphylaxis. Both aspects are important in preventing death from anaphylaxis and are covered in this review.

Pathophysiology of food-induced anaphylaxis

Food-induced anaphylaxis is a steadily increasing problem in westernized countries and now represents the leading cause of anaphylaxis in the outpatient setting, particularly in children. Much of our knowledge of the pathophysiology of food-induced anaphylaxis comes from animal studies. Food anaphylaxis in humans is thought to be entirely IgE mediated. Several features appear to be unique to these reactions; factors such as exercise can lower the "threshold" for anaphylaxis in certain susceptible individuals. Different methods of thermal processing can modify the allergenicity of food proteins. Alteration of stomach pH can allow for incomplete digestion of food proteins, leading to increased absorption of intact food allergens. Low serum platelet-activating factor acetylhydrolase may predispose to fatal food-induced anaphylaxis. With a greater understanding of the pathophysiology of food-induced anaphylaxis, novel approaches not only to identify those at risk, but to treat and ultimately prevent food-induced anaphylaxis, are on the horizon.

[Hymenoptera venom anaphylaxis and cardiovascular disease]

Preexisting cardiovascular disease may worsen the course of anaphylaxis. This is illustrated based on the example of Hymenoptera venom allergy. Fatal sting anaphylaxis is most often observed in elderly patients. During autopsy preexisting cardiovascular disease is frequently found. Preexisting cardiovascular disease in patients with anaphylaxis may also cause lasting morbidity, e.g. cerebral or myocardial infarction. Heart medications, notably beta-blockers und ACE-inhibitors may worsen the course of anaphylactic reactions due to their pharmacologic effects. Since cardiovascular diseases are much more frequent than anaphylaxis and these medications are very effective, these drugs cannot be substituted in patients with both diseases without a careful risk analysis. Epinephrine is the drug of first choice for treatment of anaphylaxis. It may however, especially following rapid intravenous administration, cause severe arrhythmias or myocardial infarction. Adrenaline should therefore preferably be given intramuscularly, or by slow intravenous infusion.

2S Albumin Storage Proteins: What Makes them Food Allergens?

2S albumin storage proteins are becoming of increasing interest in nutritional and clinical studies as they have been reported as major food allergens in seeds of many mono- and di-cotyledonous plants. This review describes the main biochemical, structural and functional properties of these proteins thought to play a role in determining their potential allergenicity. 2S albumins are considered to sensitize directly via the gastrointestinal tract (GIT). The high stability of their intrinsic protein structure, dominated by a well-conserved skeleton of cysteine residues, to the harsh conditions present in the GIT suggests that these proteins are able to cross the gut mucosal barrier to sensitize the mucosal immune system and/or elicit an allergic response. The flexible and solvent-exposed hypervariable region of these proteins is immunodominant and has the ability to bind IgE from allergic patients sera. Several linear IgE-binding epitopes of 2S albumins spanning this region have been described to play a major role in allergenicity; the role of conformational epitopes of these proteins in food allergy is far from being understood and need to be investigated. Finally, the interaction of these proteins with other components of the food matrix might influence the absorption rates of immunologically reactive 2S albumins but also in their immune response.

Practical allergy (PRACTALL) report: risk assessment in anaphylaxis

Effector mechanisms in anaphylaxis were reviewed. Current approaches to confirmation of the clinical diagnosis were discussed. Improved methods for distinguishing between allergen sensitization (which is common in the general population) and clinical risk of anaphylaxis (which is uncommon) were deliberated. Innovative techniques that will improve risk assessment in anaphylaxis in the future were described.