Table of Contents
Instant Recall: Type-I-Immediate-Type
Allergies are divided into four different types according to Coombs and Gell:
- Immediate-type allergic reaction,
- Cytotoxic-type allergic reaction,
- Immune complex-type allergic reaction,
- Delayed-type allergic reaction.
Anaphylactic shock belongs to the type 1 hypersensitivity: immediate-type allergy. Anaphylaxis is caused typically by:
- Food exposures (including nuts, eggs, soy, etc.)
- Medication (metamizole, penicillin, NSAR)
- Inhalation (pollen, latex, etc.)
The complex immunological reaction proceeds quickly. A “first exposure“ with the antigen occurs prior to any allergic reaction. The IgE-antibodies, which bind mast cells to surfaces, play an important role in this reaction. Once there is a second exposure to the same or similar allergen, the bound IgE-antibodies interlink with each other and lead to a degranulation of mast cells. This leads to the release of inflammatory mediators, especially histamine and prostaglandins, followed by vascular dilatation (which leads to a drop in blood pressure) and increase the permeability of the vessels (which leads to swelling).
Anaphylactic shock is the most severe form of the type 1 reaction. This leads to redistribution of blood volume in the peripheral circulation (distributive shock), with reduced venous return and reduced cardiac output. This leads to decreased tissue perfusion and tissue hypoxia.
|Symptoms||The release of histamine causes…|
|Bronchospasm, colic and rhinitis, conjunctivitis, bronchial asthma||Peripheral vasodilation and increased vascular permeability|
|Erythema||Accumulation of blood in the capillary bed|
|Edema, pulmonary edema||Fluid shift into the stroma|
|Flushing, dizziness, exanthema → hypotension, laryngeal edema, bronchospasm with dyspnea, tachycardia, altered mental status → circulatory failure with multiple organ failures!||Hypovolemia, hypoxia, vasodilation|
Acute Therapy of Anaphylaxis
Treatment of anaphylactic shock includes:
- Recognize the condition early (this is critical)
- Remove or discontinue (in the case of medication or other agents) the offending allergen
- Administer oxygen via face mask
- Obtain adequate (i.e. large bore) venous access as soon as possible (needed to administer medications)
- Corticosteroids (e.g. prednisolone), and H1- and H2- antihistamines intravenously (high doses)
- Epinephrine (i.m. or i.v.)- patients may not have easy venous access when in shock.
- Intravenous crystalloids to maintain volume
- Fast-acting inhaled β2-sympathomemitic.
- Recognize that a GCS- score of < 8 requires endotracheal intubation for airway protection and oxygenation.
In Order to Avoid a Shock…
- Desensitization: the specific immunotherapy (SIT) can be used for prophylactic sensitization to specific allergens, e.g. bee or wasp venom and certain types of pollen. A steady increase of the injected (subcutaneous or sublingual) antigen in minimal dosage can achieve a physiological rather than an excessive IgE-antibody-production. Especially younger patients with a monovalent allergy benefit from desensitization therapy.
- Emergency-kit: Patients should learn to use and carry on them at all times, an emergency kit, including H1-antihistamine, glucocorticoid, and epinephrine.
- Breast milk diet: reduction of developing atopic predisposition by exclusive breast-feeding during the first 4—6 months.
- Stimulating climate: in the event of pollen allergies, a relocation is an extreme form of prophylaxis.