V1.2.4. March 27, 2023
Definition and Pathophysiology (3)
“Anaphylaxis is a severe, systemic hypersensitivity reaction that is rapid in onset and characterized by life-threatening airway, breathing, and/or circulatory problems, and that is usually associated with skin and mucosal changes” (3).
Pathophysiologic changes in anaphylaxis and mediators that have been implicated in these processes (3)
As mentioned in the text, first-line treatment of anaphylaxis consists of rapid administration of epinephrine.
Although there is evidence that the mediators shown in the figure, particularly histamine and CysLTs, contribute to some of the various signs and symptoms of anaphylaxis and antihistamines are routinely administered to patients with anaphylaxis, pharmacologic targeting of such mediators represents second-line treatment and should not be considered an alternative to epinephrine.
Red indicates strong evidence for the importance of that mediator in human subjects in the development of some of the signs and symptoms listed in the adjacent box.
Blue indicates that these elements can be important in mouse models of anaphylaxis, but their importance in human anaphylaxis is not yet clear (studies in human subjects suggest that CysLTs can contribute importantly to the bronchoconstriction and enhanced vascular permeability associated with anaphylaxis).
Gray indicates elements with the potential to influence anaphylaxis, but their importance in human or mouse anaphylaxis is not yet clear. Note that some mediators (underlined) are likely to contribute to development of late consequences of anaphylaxis.
Diagnostic Criteria (2)
Clinical criteria for the diagnosis of anaphylaxis. Anaphylaxis is likely when 1 of 3 criteria are fulfilled: (1) acute onset of an illness (minutes to hours) with involvement of the skin, mucosal tissue, or both with either respiratory involvement or reduced blood pressure (BP)/associated symptom of end-organ dysfunction; or (2) ≥2 of the following that occur rapidly after exposure to a likely allergen for the patient, including (i) involvement of skin-mucosal tissue, (ii) respiratory involvement, (iii) reduced blood pressure or associated symptoms, or (iv) gastrointestinal symptoms; or (3) reduced blood pressure as a result of exposure to a known allergen trigger.
Sensitivity and specificity of diagnostic criteria (1)
Proposed diagnostic criteria by the National Institute of Allergy and Infectious Diseases/Food Allergy and Anaphylaxis Network (NIAID/ FAAN)(2), are proposed to be useful to the emergency department:
Emergency anaphylaxis management algorithm (2)
Suggested key clinical advice (4)
Severe anaphylaxis and/or the need for >1 dose of epinephrine to treat anaphylaxis are risk factors for biphasic anaphylaxis. Additional risk factors include wide pulse pressure, unknown anaphylaxis trigger, cutaneous signs and symptoms, and drug trigger in children.
Extended observation is suggested for patients with resolved severe anaphylaxis and/or those with need for >1 dose of epinephrine.
Antihistamines and/or glucocorticoids are not reliable interventions to prevent biphasic anaphylaxis but may be considered as secondary treatment.
Evidence supports a role for antihistamine and/or glucocorticoid premedication in specific chemotherapy protocols and rush aeroallergen immunotherapy.
Evidence is lacking to support the routine use of antihistamines and/or glucocorticoid premedication in patients receiving low- or iso-osmolar contrast material to prevent recurrent RCM anaphylaxis.
Administer epinephrine as the first-line pharmacotherapy for uniphasic and/or biphasic anaphylaxis.
Do not delay the administration of epinephrine for anaphylaxis.
After diagnosis and treatment of anaphylaxis, all patients should be kept under observation until symptoms have fully resolved.
All patients with anaphylaxis should receive education about anaphylaxis, risk of recurrence, trigger avoidance, self-injectable epinephrine, and thresholds for further care, and they should be referred to an allergist for follow-up evaluation.
Campbell RL, Hagan JB, Manivannan V, et al. Evaluation of national institute of allergy and infectious diseases/food allergy and anaphylaxis network criteria for the diagnosis of anaphylaxis in emergency department patients. J Allergy Clin Immunol. 2012;129(3):748-752. doi:10.1016/j.jaci.2011.09.030
Journal of Allergy and Clinical Immunology (Open Access)
Campbell RL, Li JT, Nicklas RA, Sadosty AT; Members of the Joint Task Force; Practice Parameter Workgroup. Emergency department diagnosis and treatment of anaphylaxis: a practice parameter. Ann Allergy Asthma Immunol. 2014;113(6):599-608. doi:10.1016/j.anai.2014.10.007
Annals of Allergy and Immunology (Open Access)
Reber LL, Hernandez JD, Galli SJ. The pathophysiology of anaphylaxis. J Allergy Clin Immunol. 2017;140(2):335-348. doi:10.1016/j.jaci.2017.06.003
JACI (Open Access)
Shaker MS, Wallace DV, Golden DBK, et al. Anaphylaxis-a 2020 practice parameter update, systematic review, and Grading of Recommendations, Assessment, Development and Evaluation (GRADE) analysis. J Allergy Clin Immunol. 2020;145(4):1082-1123. doi:10.1016/j.jaci.2020.01.017
Journal of Allergy and Clinical Immunology (Open Access)
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