Accidents anaphylactiques

Abstract

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.