Anaphylaxis is a severe and potentially life-threatening allergic reaction that requires immediate treatment. The condition affects multiple organ systems simultaneously and can develop rapidly. In this article, we explain what anaphylaxis is, how it differs from a regular allergy, and how anaphylaxis is treated.

From Allergy to Anaphylaxis

An allergy is a type of hyperreactive immune response where the body reacts abnormally strongly to a substance that is usually harmless. Such a substance is called an allergen. Allergens are usually proteins and can, for example, come from pets, nuts, shellfish, medications, insect venom, or pollen.

When an allergic person's immune system comes into contact with an allergen it has previously been exposed to, it can trigger an allergic reaction. This can, among other things, cause smooth muscles in the airways to contract, blood vessels to dilate, and mucous membranes to become irritated and swollen. These are symptoms many recognize from common pollen allergies.

The symptoms are due to the allergen binding to E-type immunoglobulins (IgE) on the surface of basophil granulocytes and mast cells, which in turn stimulates the release of substances such as histamine, leukotrienes, and prostaglandins. These substances contribute to local inflammation in the tissue and, in severe reactions, can also cause systemic symptoms.

What is Anaphylaxis?

Anaphylaxis is a severe and dysregulated allergic reaction that affects multiple organ systems. Patients experiencing an anaphylactic reaction may experience severe respiratory distress, low blood pressure, vomiting, and abdominal pain, among other symptoms. Untreated, anaphylaxis can be fatal.

To define anaphylaxis, we state that the patient must have a severe allergic reaction with symptoms from at least two of the following organ systems:

• Skin and mucous membranes
• Lungs and airways
• Circulatory system
• Gastrointestinal system

Treatment of Anaphylaxis

Patients with anaphylaxis are managed according to standard ABCDE principles. Patients with breathing difficulties often feel better sitting upright, while patients with circulatory failure often do best lying down.

The most important pharmacological intervention for anaphylaxis is intramuscularly administered adrenaline. This is life-saving and time-critical treatment. Adrenaline counteracts many of the severe symptoms of anaphylaxis, including by dilating bronchi, constricting blood vessels, and stopping the release of histamine.

Patients who are particularly susceptible to anaphylactic reactions often have adrenaline autoinjectors available, such as EpiPen. Such autoinjectors are also appropriate for healthcare personnel who do not regularly work with acute medicine. Adrenaline is a powerful medication that must be dosed correctly to avoid serious side effects. It has a short half-life of approx. 2 minutes, and repeated dosing may be necessary. A new dose is recommended if symptoms return within 5–10 minutes.

Using an EpiPen

• Hold a clenched fist around the pen – avoid holding either end.
• Remove the blue safety cap.
• Firmly press the orange end of the pen against the middle of the patient's outer thigh. You can inject through regular clothing.
• Press firmly until you hear a click. Hold the pen in the thigh for 10 seconds before removing it.

AVOKADO – a mnemonic for the treatment of anaphylaxis

The mnemonic AVOKADO helps you remember the most important medical interventions for anaphylaxis. Adrenaline is the most important and is always prioritized first.

A - Adrenaline: 0.3-0.5 mg i.m. EpiPen® contains 0.3 mg.
V - Volume: 500-1000 ml Ringer-Acetate as a bolus dose i.v.
O - Oxygen: 10-15 L via mask with reservoir.
K - Corticosteroids: Solu-Cortef 100-250 mg i.v.
A - Antihistamine: Dexchlorpheniramine 10 mg i.m./5-10 mg i.v.
D - Diagnosis: What was the trigger?
O - Observation: Patients with severe anaphylaxis may develop new symptoms after treatment and should be observed for at least 24 hours in hospital due to the risk of recurrence.