Anaphylaxis
Anaphylaxis | |
---|---|
intravenous fluids[1] | |
Frequency | 0.05–2%[3] |
Anaphylaxis is a serious, potentially fatal
Common causes include allergies to
The primary treatment of anaphylaxis is
Worldwide, 0.05–2% of the population is estimated to experience anaphylaxis at some point in life.[3] Globally, as underreporting declined into the 2010s, the rate appeared to be increasing.[3] It occurs most often in young people and females.[8][9] About 99.7% of people hospitalized with anaphylaxis in the United States survive.[10]
Etymology
The word is derived from
romanized: phylaxis lit. 'protection'.[11]Signs and symptoms
Anaphylaxis typically presents many different symptoms over minutes or hours
Skin
Symptoms typically include generalized
Respiratory
Respiratory symptoms and signs that may be present include
Cardiovascular
While a fast heart rate caused by low blood pressure is more common,[16] a Bezold–Jarisch reflex has been described in 10% of people, where a slow heart rate is associated with low blood pressure.[9] A drop in blood pressure or shock (either distributive or cardiogenic) may cause the feeling of lightheadedness or loss of consciousness.[17] Rarely very low blood pressure may be the only sign of anaphylaxis.[15]
Other
Gastrointestinal symptoms may include severe crampy
Causes
Anaphylaxis can occur in response to almost any foreign substance.
Food and alcohol
Many foods can trigger anaphylaxis; this may occur upon the first known ingestion.
Medication
Any medication may potentially trigger anaphylaxis. The most common are
The frequency of a reaction to an agent partly depends on the frequency of its use and partly on its intrinsic properties.[30] Anaphylaxis to penicillin or cephalosporins occurs only after it binds to proteins inside the body with some agents binding more easily than others.[13] Anaphylaxis to penicillin occurs once in every 2,000 to 10,000 courses of treatment, with death occurring in fewer than one in every 50,000 courses of treatment.[13] Anaphylaxis to aspirin and NSAIDs occurs in about one in every 50,000 persons.[13] If someone has a reaction to penicillin, his or her risk of a reaction to cephalosporins is greater but still less than one in 1,000.[13] The old radiocontrast agents caused reactions in 1% of cases, while the newer lower osmolar agents cause reactions in 0.04% of cases.[30]
Venom
Venom from stinging or biting insects such as Hymenoptera (ants, bees, and wasps) or Triatominae (kissing bugs) may cause anaphylaxis in susceptible people.[8][31][32] Previous reactions that are anything more than a local reaction around the site of the sting, are a risk factor for future anaphylaxis;[33][34] however, half of fatalities have had no previous systemic reaction.[35]
Risk factors
People with
Pathophysiology
Anaphylaxis is a severe
Interleukin (IL)–4 and IL-13 are cytokines important in the initial generation of antibody and inflammatory cell responses to anaphylaxis.[citation needed]
Immunologic
In the immunologic mechanism,
Non-immunologic
Non-immunologic mechanisms involve substances that directly cause the
Diagnosis
Anaphylaxis is diagnosed on the basis of a person's signs and symptoms.[3] When any one of the following three occurs within minutes or hours of exposure to an allergen there is a high likelihood of anaphylaxis:[3]
- Involvement of the skin or mucosal tissue plus either respiratory difficulty or a low blood pressurecausing symptoms
- Two or more of the following symptoms after a likely contact with an allergen:
- a. Involvement of the skin or mucosa
- b. Respiratory difficulties
- c. Low blood pressure
- d. Gastrointestinalsymptoms
- Low blood pressure after exposure to a known allergen
Skin involvement may include: hives, itchiness or a swollen tongue among others. Respiratory difficulties may include: shortness of breath, stridor, or low oxygen levels among others. Low blood pressure is defined as a greater than 30% decrease from a person's usual blood pressure. In adults a systolic blood pressure of less than 90 mmHg is often used.[3]
During an attack, blood tests for tryptase or histamine (released from mast cells) might be useful in diagnosing anaphylaxis due to insect stings or medications. However these tests are of limited use if the cause is food or if the person has a normal blood pressure,[3] and they are not specific for the diagnosis.[18]
Classification
There are three main classifications of anaphylaxis.
- Anaphylactic shock is associated with systemic vasodilation that causes low blood pressure which is by definition 30% lower than the person's baseline or below standard values.[15]
- Biphasic anaphylaxis is the recurrence of symptoms within 1–72 hours after resolution of an initial anaphylactic episode.[37] Estimates of incidence vary, between less than 1% and up to 20% of cases.[37][38] The recurrence typically occurs within 8 hours.[9] It is managed in the same manner as anaphylaxis.[8]
- Anaphylactoid reaction, non-immune anaphylaxis, or pseudoanaphylaxis, is a type of anaphylaxis that does not involve an allergic reaction but is due to direct mast cell degranulation.[9][39] Non-immune anaphylaxis is the current term, as of 2018, used by the World Allergy Organization[39] with some recommending that the old terminology, "anaphylactoid", no longer be used.[9]
Allergy skin testing
Skin testing is available to confirm penicillin allergies, but is not available for other medications.[18] Non-immune forms of anaphylaxis can only be determined by history or exposure to the allergen in question, and not by skin or blood testing.[39]
Differential diagnosis
It can sometimes be difficult to distinguish anaphylaxis from asthma, syncope, and panic attacks.[3] Asthma however typically does not entail itching or gastrointestinal symptoms, syncope presents with pallor rather than a rash, and a panic attack may have flushing but does not have hives.[3] Other conditions that may present similarly include: scrombroidosis and anisakiasis.[9]
Post-mortem findings
In a person who died from anaphylaxis, autopsy may show an "empty heart" attributed to reduced venous return from vasodilation and redistribution of intravascular volume from the central to the peripheral compartment.[40] Other signs are laryngeal edema, eosinophilia in lungs, heart and tissues, and evidence of myocardial hypoperfusion.[41] Laboratory findings could detect increased levels of serum tryptase, increase in total and specific IgE serum levels.[41]
Prevention
Avoidance of the trigger of anaphylaxis is recommended. In cases where this may not be possible, desensitization may be an option.
Management
Anaphylaxis is a medical emergency that may require resuscitation measures such as airway management, supplemental oxygen, large volumes of intravenous fluids, and close monitoring.[8] Passive leg raise may also be helpful in the emergency management.[43]
Administration of intravenous fluid bolus and epinephrine is the treatment of choice with
Epinephrine
People on β-blockers may be resistant to the effects of epinephrine.[9] In this situation if epinephrine is not effective intravenous glucagon can be administered which has a mechanism of action independent of β-receptors.[9]
If necessary, it can also be given
Adjuncts
Preparedness
People prone to anaphylaxis are advised to have an allergy action plan. Parents are advised to inform schools of their children's allergies and what to do in case of an anaphylactic emergency. The action plan usually includes use of epinephrine autoinjectors, the recommendation to wear a medical alert bracelet, and counseling on avoidance of triggers.[50] Immunotherapy is available for certain triggers to prevent future episodes of anaphylaxis. A multi-year course of subcutaneous desensitization has been found effective against stinging insects, while oral desensitization is effective for many foods.[14]
Prognosis
In those in whom the cause is known and prompt treatment is available, the prognosis is good.
Epidemiology
The number of people who get anaphylaxis is 4–100 per 100,000 persons per year,
Rates appear to be increasing: the numbers in the 1980s were approximately 20 per 100,000 per year, while in the 1990s it was 50 per 100,000 per year.[14] The increase appears to be primarily for food-induced anaphylaxis.[54] The risk is greatest in young people and females.[8][9]
Anaphylaxis leads to as many as 500–1,000 deaths per year (2.7 per million) in the United States, 20 deaths per year in the United Kingdom (0.33 per million), and 15 deaths per year in Australia (0.64 per million).[9] Another estimate from the United States puts the death rate at 0.7 per million.[55] Mortality rates have decreased between the 1970s and 2000s.[56] In Australia, death from food-induced anaphylaxis occur primarily in women while deaths due to insect bites primarily occur in males.[9] Death from anaphylaxis is most commonly triggered by medications.[9]
History
The conditions of anaphylaxis has been known since ancient times.
Richet and Portier extracted a toxin called hypnotoxin from their collection of jellyfish (but the real source was later identified as
In 1902, Richet introduced the term aphylaxis to describe the condition of lack of protection. He later changed the term to anaphylaxis on grounds of
Research
There are ongoing efforts to develop
References
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Clinically, anaphylaxis is considered likely to be present if any one of three criteria is satisfied within minutes to hours
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External links
- Anaphylaxis at Curlie
- National Institute for Health and Clinical Excellence. Clinical guideline 134: Anaphylaxis: assessment to confirm an anaphylactic episode and the decision to refer after emergency treatment for a suspected anaphylactic episode. London, 2011. and Anaphylaxis pathway
- "Anaphylaxis". MedlinePlus. U.S. National Library of Medicine.