L'anaphylaxie est la manifestation la plus grave des reactions d'hypersensibilite immediate, mediees par les immunoglobulines E. De nombreux allergenes peuvent etre incrimines : allergenes proteiques (hymenopteres, aliments, enzymes, pollens, latex ...), polysaccharidiques (dextrans, amidons ...), haptenes (medicaments, produits de contraste, oxyde d'ethylene...). La majeure partie des chocs est d'origine medicamenteuse (antibiotiques, curares), mais la frequence des chocs d'origine alimentaire est en nette augmentation. Des reactions croisees existent entre latex et certains aliments. Le tableau clinique est explique par les mediateurs liberes : histamine, leucotrienes, prostaglandines, thromboxane, facteur d'agregation plaquettaire. Il peut etre de gravite variable, potentiellement mortel si le traitement vasoconstricteur n'est pas rapidement administre. Des formes gravissimes, resistantes au traitement ont ete decrites. Des facteurs favorisants ont ete identifies en ce qui concerne le latex, l'allergie alimentaire, ce qui n'est pas le cas avec les medicaments de l'anesthesie (curares en particulier). Les investigations diagnostiques doivent etre menees conjointement aux manoeuvres de reanimation (dosage de tryptase, histamine et certains anticorps specifiques) et secondairement pour identifier l'allergene responsable (tests cutanes). Le centre de pharmacovigilance doit etre obligatoirement informe en cas d'origine medicamenteuse, ou la materiovigilance s'il s'agit de latex. Le traitement du choc anaphylactique ne doit souffrir d'aucun retard et repose sur l'adrenaline dont les doses et modalites d'administration doivent etre modulees suivant la gravite de la reaction et son evolution. Les patients ayant fait un choc anaphylactique doivent etre precisement informes de l'allergene responsable et des mesures de prevention pour eviter les rechutes qui risqueront d'etre mortelles (eviction des allergenes, trousse d'urgence, desensibilisation eventuelle).
Anaphylaxis is the most severe manifestation among immediate hypersensitivity reactions due to IgEs. A lot of allergens may be responsible such as : proteins (hymenoptere, foods, enzymes, pollens, latex...) polysaccharides (dextrans, hydroxyethylstarch...), haptens (drugs, contrast media, ethylene oxide...). Drugs are responsible for the majority of anaphylactic shocks (antibiotics, muscle relaxants) but the incidence of food allergy is increasing for some years. Cross-reactive sensitization exists between latex and fruit. Several mediators are suddenly released during anaphylaxis: histamine, leucotrienes, prostaglandines, thromboxane, platelet aggregating factor... explaining cardiovascular, cutaneous and bronchial symptoms. The clinical symptoms of anaphylaxis may be of variable severity, classified in 4 grades. From grade 3 the reaction is life-threatening, and commands adrenaline injection rapidly. Extremely severe reactions have been described, resistant to adrenaline, leading to death or severe sequellae. Some risk factors of sensitization and anaphylaxis have been identified for latex and food allergy, but not for muscle relaxants in anaesthesia. Diagnostic investigations must be managed during the resuscitation (= immediate investigations on blood samples for measurement of tryptase, histamine, specific IgEs) and 4-6 weeks later on to identify the allergen responsible for this reaction (= secondary investigations by allergic cutaneous tests). It is mandatory to report the event to the pharmacovigilance centre if a drug is suspected to be the cause, and to the materiovigilance centre of the local institution if latex is suspected to be involved. Treatment of anaphylaxis is essentially based on epinephrine, administered by bolus in titrated doses. Treatment must be adapted to the severity of the clinical situation, to the patient's history, to the associated treatment and to the patient's response to the emergency treatment. Patients who have experienced anaphylaxis must be informed about responsible allergen and preventive measures to avoid relapses.