Anaphylaxis

From WikiMD free medical encyclopedia
Jump to: navigation, search

In medicine, anaphylaxis is a severe and rapid systemic allergic reaction. Anaphylaxis occurs when a person is exposed to a trigger substance, called an allergen, to which they have become sensitized. Minute amounts of allergens may cause a life-threatening anaphylactic reaction. Anaphylaxis may occur after ingestion, inhalation, skin contact or injection of an allergen. The most severe type of anaphylaxis—anaphylactic shock—will usually lead to death in minutes if left untreated.

The word is from New Latin (derived from Greek ἀνα-/ana, meaning "up, again, back, against") + φύλαξις/phylaxis, meaning "guarding, protection"—cf. prophylaxis.)

Emergency treatment

Anaphylactic shock is a life-threatening medical emergency because of rapid constriction of the airway, often within minutes of onset. Calling for help immediately is important, as brain damage occurs rapidly without oxygen. Anaphylactic shock requires advanced medical care immediately; but other first aid measures include rescue breathing (part of CPR) and administration of epinephrine. Rescue breathing may be hindered by the constricted airways but can help if the victim stops breathing on their own. If the patient has previously been diagnosed with anaphylaxis, they may be carrying an EpiPen (or similar device) for immediate administration of epinephrine (adrenaline) by a layperson to help keep open the airway. Repetitive administration can cause tachycardia (rapid heartbeat) and occasionally ventricular tachycardia with heart rates potentially reaching 240 beats per minute, which can also be fatal. This is why some protocols advise Intramuscular injection of only 0.3–0.5mL of a 1:1,000 dilution. The epinephrine will prevent worsening of the airway constriction, and may be life-saving.

Epinephrine will act on Beta-2 adrenergic receptors in the lung as a powerful bronchodilator relieving allergic or histamine-induced acute asthmatic attack or anaphylaxis. Tachycardia results from stimulation of Beta-1 adrenergic receptors of the heart increasing contractility (ionotropic effect) and frequency (chronotropic effect) and thus cardiac output.

Symptoms

Symptoms of anaphylaxis are related to the action of immunoglobulin E (IgE) and other anaphylatoxins, which act to release histamine and other mediator substances from mast cells (degranulation). In addition to other effects, histamine induces vasodilation and bronchospasm (constriction of the airways).

Symptoms can include the following:

The time between ingestion of the allergen and anaphylaxis symptoms can vary for some patients depending on the amount of allergen ingested and sensitivity. Symptoms can appear immediately, or can be delayed by half an hour to several hours after ingestion. However, symptoms of anaphylaxis usually appear very quickly once they do begin.

Causes

Peanuts are a common trigger of anaphylactic reactions.

Common causative agents in humans include:

Transfusion of incompatible blood products may lead to extremely similar symptoms, albeit for substantially different biochemical reasons.

Passive transfer

The anaphylactic reaction is mediated by antibodies. Anaphylactic sensitivity can be transferred to a normal (non-sensitive) recipient by means of serum containing such antibodies. This is then called passive transfer of the allergy or hypersensitivity.

The source of antibody may be from the same species, e.g. the human species, for which the predominant immunoglobulin involved is of the IgE class. Some known cases of deaths resulting from passive transfer involve organ transplants. It may also be transferred from animals of a different species. For example, a guinea pig may be sensitized by an intravenous injection of rabbit antibody to ovalbumin. When challenged (that is, brought in contact) with ovalbumin 48 hours later, the guinea pig will suffer fatal anaphylactic shock.

Treatment

Paramedic treatment in the field may include injection with epinephrine, administration of oxygen therapy and, if necessary, intubation during transport to advanced medical care. In profuse angioedema, cricothyroidectomy or tracheotomy may be required to maintain oxygenation.

The clinical treatment of anaphylaxis by a doctor and in the hospital setting aims to treat the cellular hypersensitivity reaction as well as the symptoms. Antihistamine drugs (which inhibit the effects of histamine at histamine receptors) are given but are usually not sufficient in anaphylaxis, and high doses of intravenous corticosteroids are often required. Hypotension is treated with intravenous fluids and sometimes vasoconstrictor drugs. For bronchospasm, bronchodilator drugs (e.g. Salbutamol, known as Albuterol in the United States) are used. In severe cases, immediate treatment with epinephrine can be lifesaving. Supportive care with mechanical ventilation may be required.

Patients must be monitored for four hours after being transported to medical care for the possibility of biphasic reactions (recurrence of anaphylaxis) [1].

See also

References

  • Krause, RS. 2005. Anaphylaxis. Emedicine.com.
  • Howland, R. 2006. Lippincott's Review of Pharmacology, 3rd Edition
  • Gomella, LG. 2005. Clinician's Pocket Drug Reference. Drug Manual.

WikiMD Sponsors - W8MD Weight Loss, Sleep and MedSpa Centers

Pronounced weightMD, our state of the art W8MD weight loss, sleep, holistic IV nutrition and aesthetic medicine programs can help you not only to lose weight, and sleep better but also look your best! Since its inception in 2011, W8MD’s insurance physician weight loss program has successfully helped thousands of patients.

W8MD Weight Loss

W8MD’s Physician weight loss is unique in many ways with a comprehensive multidisciplinary approach to weight loss. Weight Loss Success Stories....

W8MD Sleep Services

Sleep medicine program uses state of the art technology to diagnose and treat over 80 different sleep disorders. W8MD Sleep Services…

W8MD Medical Aesthetic Services

Medical aesthetic program offers a wide variety of advanced laser skin treatments including oxygen super facials, photofacials and Affordable Botox. W8MD Aesthetic Services…

IM and IV nutrition therapy includes booster shots for B12, vitamin B complex, Vitamin C, Detox treatments and IV nutrition therapy. W8MD IV Nutrition…

W8MD weight loss | Philadelphia medical weight loss | NYC medical weight loss | NJ medical weight loss

W8MD Weight Loss, Sleep & Medical Aesthetics

Intro to W8MD Weight Loss, Sleep & Medical Aesthetics


Disclaimer: The entire contents of WIKIMD.ORG are for informational purposes only and do not render medical advice or professional services. If you have a medical emergency, you should CALL 911 immediately! Given the nature of the wiki, the information provided may not be accurate and or incorrect. Use the information on this wiki at your own risk! See full Disclaimers.WikiMD is supported by W8MD Weight loss, Poly-Tech Sleep & Medical Aesthetic Centers of America.