Anaphylaxis (also known as anaphylactic shock or reaction) is an acute severe systemic Type I hypersensitivity reaction, commonly presenting with urticaria/angioedema, hypotension and bronchial hyperreactivity. It may be fatal.
Anaphylactoid reactions result from non-immune system mediated mechanisms. However they are clinically indistinguishable from anaphylactic reactions with similar risks of multiorgan failure and death. From a patient perspective anaphylactoid and anaphylactic reactions are managed identically 5.
The published epidemiological data from the USA, UK and Australia, demonstrates an incidence rate of anaphylaxis of 7 to 50 cases per 100,000 per annum. The number of deaths is estimated to be up to 3 per 1,000,000 per year.
There is no gender preference in adults; in prepubescent children, it is more common in boys 1.
The typical presentation affects the skin, chest, GI tract and cardiovascular system. Often the signs and symptoms are indolent in onset and initially mild, such as itching and rashes.
- systemic hypotension
However, up to 20% patients with anaphylaxis lack any evidence of circulatory compromise or dermatological sequelae 2.
In radiology, approximately 1 in 40,000 patients will experience anaphylaxis from iodinated contrast media. Most anaphylaxis will occur within twenty minutes of administration of IV contrast agents, although longer delays are occasionally seen.
Treatment and prognosis
Treatment protocols may vary by institution, however usually involve the administration of epinephrine (epinephrine) and oxygen with measures to protect the patient's airway if necessary. Although fatal outcomes happen, they are rare with proper treatment 6.
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- 2. Tupper J, Visser S. Anaphylaxis: A review and update. (2010) Canadian family physician Medecin de famille canadien. 56 (10): 1009-11. Pubmed
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- 4. Reber LL, Hernandez JD, Galli SJ. The pathophysiology of anaphylaxis. (2017) The Journal of allergy and clinical immunology. 140 (2): 335-348. doi:10.1016/j.jaci.2017.06.003 - Pubmed
- 5. Lagopoulos V, Gigi E. Anaphylactic and anaphylactoid reactions during the perioperative period. (2011) Hippokratia. 15 (2): 138-40. Pubmed
- 6. Turner PJ, Jerschow E, Umasunthar T, Lin R, Campbell DE, Boyle RJ. Fatal Anaphylaxis: Mortality Rate and Risk Factors. (2017) The journal of allergy and clinical immunology. In practice. 5 (5): 1169-1178. doi:10.1016/j.jaip.2017.06.031 - Pubmed