Anaphylaxis: prevention and treatment

If it can threaten life, we can stop, but also prevent, its most serious manifestations. Professor Pascal Demoly, Head of the Department of Pulmonology at Montpellier University Hospital tells us what you need to know.

Paris match. What does this term refer to?
Professor Pascal Demoly. A form of so-called “immediate” allergy, which is a severe reaction of generalized hypersensitivity that has a rapid onset (a few minutes to a few hours, averaging fifteen minutes) and is life-threatening. It is characterized by: 1. Sudden onset of upper or lower airway spasm. The air remains “locked” in the lungs without being able to exit or enter, a dual sensation experienced by patients. 2. A massive vasodilatation of the vessels at the origin of severe hypotension, capable of defusing the heart. 3. Extreme weakness with confusion and sometimes coma. 4. Very often (90% of cases) diffuse vascular edema called Quincke’s angioedema is associated. It can affect the skin (erythema, urticaria) and/or the digestive tract (severe pain, nausea, vomiting, diarrhea) and/or the larynx, the most feared condition (danger of suffocation).

What are its incidence and triggers?
Almost 3% of French people will have at least one anaphylactic event in their lifetime. According to the studies, the annual incidence (increasing) varies from 1 to 8 cases per 100,000 inhabitants. It affects both children and adults of both sexes. A reason called “atopic” (family of allergy sufferers, certain biological predispositions) favors them. It is triggered by an allergen, which may be, in order of frequency, a drug (antibiotic, curare, chemotherapy, immunotherapy, etc.), a food (seafood, nuts, dairy, etc.), or a hymenoptera (bee, wasp). , hornet, ant) ​​especially in summer. A variety of other products (e.g. latex) are more rarely the allergen. Vaccinations are only in exceptional cases (1 case in 100,000).

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For vulnerable or predisposed individuals, the saving gesture is a self-injection of adrenaline

What is the biological mechanism and the main risk?
Allergic anaphylaxis begins in two stages: 1. A first asymptomatic exposure to the allergen sensitizes the person by inducing the secretion of IgE antibodies (by white blood cells called “plasmocytes”), which attach to certain immune cells called immune cells attach “mast cells”. 2. With a second contact with the allergen, the mast cells, under the action of IgE, release enormous amounts of active substances (especially histamine), which have a double effect: they dilate the vessels and “spasm” the bronchi. The extreme variant is anaphylactic shock, which combines vascular collapse and acute shortness of breath with multiple organ failure. It is estimated that around 10% of these shocks result in death. 3. Non-allergic anaphylaxis (20% of cases) also exists, toxic (due to overdose) or due to dysregulation of mast cells.

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How is anaphylactic shock treated?
The only sensible urgent treatment is intramuscular injection of adrenaline. It acts immediately against the dilatation of the vessels, which it revitalises, and against the spasms of the bronchi, which it relieves. For vulnerable or predisposed individuals, the life-saving gesture (which can be done through the pants) is self-injection into the outer-middle third of the thigh with an adrenaline pen. There are three dosages: 0.15 mg in children, 0.3 mg and 0.5 mg in adults. If there is no improvement within five to ten minutes, they must be repeated. It is absolutely necessary to avoid giving corticosteroids as a first intention (effect too late) and to see what happens, as some practitioners continue to do. Without a doctor, call 15. Place the shocked person on their back with their legs raised in the event of severe hypotension, lay them on their side if they are vomiting, lay them semi-sitting if they are breathing improperly. Remove allergen when identified (insect, food).

Also read. Food allergies: what treatment?

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And preventive?
Desensitization is sometimes possible, particularly to hymenoptera (100% healing against wasp stings, 80% against bee stings). Predisposed individuals should always carry an adrenaline pen. I name three: Emerade, the most practical (the only one equipped with a long needle that ensures intramuscular administration with a single gesture, with three doses available). And two other good alternatives: Jext and Epipen.

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