Anaphylaxis

Anaphylaxis is a rare, life-threatening hypersensitive response to insect proteins which is characterized by contraction of smooth muscle and dilation of capillaries due to release of pharmacologically active substances. Anaphylaxis occurs within a few minutes after exposure. The clinical response depends upon the tissue that is affected. Examples of local anaphylaxis include asthma, hay fever and edema of the tissues of the throat. Anaphylactic shock is often a severe, and sometimes fatal, systemic reaction in a susceptible individual characterized especially by respiratory symptoms, fainting, itching, and hives. For some reason all the common allergies such as hayfever, allergic asthma and food allergy have become more common.

True anaphylaxis is caused by immunoglobulin E (IgE)-mediated release of mediators from mast cells and basophils. Researchers have definite ideas about why this might be so. The classic form, described in 1902, involves prior sensitization to an allergen with later re-exposure, producin symptoms via an immunologic mechanism. An anaphylactoid reaction produces a very similar clinical syndrome but is not immune-mediated. The annual incidence of anaphylactic reactions is about 30 per 100,000 persons, and individuals with asthma, eczema, or hay fever are at greater relative risk of experiencing anaphylaxis.

Anaphylactoid (anaphylaxis-like) or pseudoallergic reactions are similar to anaphylaxis. However, they are not mediated by antigen-antibody interaction, but result from substances acting directly on mast cells and basophils, causing mediator release or acting on tissues such as anaphylotoxins of the complement cascade. Idiopathic (nonallergic) anaphylaxis occurs spontaneously and is not caused by an unknown allergen. Munchausen's anaphylaxis is a purposeful self-induction of true anaphylaxis. All forms of anaphylaxis present the same and require the same rigorous diagnostic and therapeutic intervention.

Anaphylaxis is a life threatening allergic reaction that affects millions of Americans every year. Anaphylaxis can be caused by a variety of allergens , with the most common being food , medications , insect venom , and latex . If this problem is untreated, it results in shock, respiratory and cardiac failure, and death. The immediate treatment is the use of adrenalin (epinephrine) to counteract the effects- this is usually given as an injection. Anaphylaxis may occur after ingestion, inhalation, skin contact or injection of a trigger substance. Every patient prone to anaphylaxis should have an "allergy action plan" on file at school, home or in their office to aid family members, teacher and/or co-workers in case of an anaphylactic emergency. The Asthma and Allergy Foundation of America provides a free "plan" form anyone can print from their site. Action plans are considered essential to quality emergency care.

Causes of Anaphylaxis

Some cause are listed here :

• Aspirin and nonsteroidal anti-inflammatory drugs
• Anaphylaxis is usually thought of as an IgE-mediated allergic reaction to such things as foods, insect venoms, drugs, and latex
• Entry of the allergen into your blood stream provokes the release of massive amounts of histamine and other chemicals
• The most common agents leading to anaphylaxis are drugs , especially antibiotics like penicillin, foods and insect stings (bees and wasps).
• Additionally, exercise can trigger anaphylaxis if the activity occurs after eating allergy-provoking food.
• The release of mediators such as histamine from the mast cells and basophils is responsible for the immediate clinical manifestations of anaphylaxis
• Foods: especially nuts , some kinds of fruit, fish and less commonly spices
• Drugs: Especially penicillins, anaesthetic drugs, some intravenous infusion liquids, and things injected during x-rays. Aspirin and other painkillers (called NSAIDs) can produce very similar reactions.
• Bee or wasp (yellow jacket) stings when these cause faintness, difficulty in breathing, or rash or swelling of a part of the body which has not been stung
• Wrong diagnosis of anaphylaxis: a proportion (about 10%) of people sent to specialists with a diagnosis of anaphylaxis have a mistaken diagnosis and have not had anaphylaxis

Symptoms of Anaphylaxis

Symptoms of anaphylaxis can vary from mild to severe and are potentially deadly. Here is a list of possible symptoms that may occur alone or in any combination:

• Breathing: wheezing, shortness of breath, throat tightness, cough, hoarse voice, chest pain/tightness, nasal congestion/hay fever-like symptoms, trouble swallowing
• Stomach: nausea, pain/cramps, vomiting, diarrhea, itchy mouth/throat
• Circulation: pale/blue color, poor pulse, passing-out, dizzy/lightheaded, low blood pressure, shock
• Sudden feeling of extreme anxiety or apprehension.
• Itchy skin or a nettle-rash (urticaria, hives).
• Faintness, collapse or unconsciousness due to very low blood pressure.
• Abdominal cramps, vomiting or diarrhoea .
• Swelling of an area larger than the sting site
• Drop in blood pressure and narrowing of the airways.
• If the person loses consciousness, raise their feet while waiting for medical assistance. Keep them warm and make sure their airway remains open.

Treatment and Prevention of Anaphylaxis

The treatment of anaphylaxis should follow established principles for emergency resuscitation. Anaphylaxis has a highly variable presentation, and treatment must be individualized for a patient's particular symptoms and their severity. Treatment recommendations are based on clinical experience, understanding pathologic mechanisms, and the known action of various drugs. Rapid therapy is of utmost importance.

At the first sign of anaphylaxis the patient should be treated with epinephrine. Next, the clinician should determine whether the patient is dyspneic or hypotensive. Airway patency must be assessed, and if the patient has suffered cardiopulmonary arrest, basic cardiopulmonary resuscitation must be instituted immediately. If shock is present or impending, the legs should be elevated and intravenous fluids administered. Epinephrine is the most important single agent in the treatment of anaphylaxis, and its delay in or failure to be administered is more problematic than its administration.

Treatment of anaphylaxis consists of both short- and long-term management . The immediate goal is to maintain an adequate airway and support the blood pressure. Patients having severe reactions should be given oxygen. If they seem to be having trouble breathing, lay them on the ground and tilt their head back. This helps get the tongue out of the way of air flow.

• Advise patient to keep epinephrine self-injection kit and oral diphenhydramine (Benadryl) for future exposures.
• Avoid prescribing beta blockers, angiotensin-converting enzyme inhibitors, angiotensin-II receptor blockers, monoamine oxidase inhibitors, and some tricyclic antidepressants.
• Avoid administering cross-reactive agents.
• Refer to allergist if causative agent or diagnosis is unclear, if in-depth patient education is needed, or if reactions are recurrent.

Diagnosis of Anaphylaxis

Because of the profound and dramatic presentation, the diagnosis of anaphylaxis is usually readily apparent. When sudden collapse occurs in the absence of urticaria or angioedema, other diagnoses must be considered, although shock may be the only symptom of Hymenoptera anaphylaxis. These include cardiac arrhythmia, myocardial infarction, other types of shock (hemorrhagic, cardiogenic, endotoxic), severe cold urticaria, aspiration of food or foreign body, insulin reaction, pulmonary embolism, seizure disorder, vasovagal reaction, hyperventilation, globus hystericus, and factitious allergic emergencies. The most common is vasovagal collapse after an injection or a painful stimulation.

In vasovagal collapse, pallor and diaphoresis are common features associated with presyncopal nausea. There is no pruritus or cyanosis. Respiratory difficulty does not occur, the pulse is slow, and the blood pressure can be supported without sympathomimetic agents. Symptoms are almost immediately reversed by recumbency and leg elevation. Hereditary angioedema must be considered when laryngeal edema is accompanied by abdominal pain. This disorder usually has a slower onset, and lacks urticaria and hypotension, and there is often a family history of similar reactions. There is also a relative resistance to epinephrine, but epinephrine may have life-saving value in hereditary angioedema.

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