Procedure I

Definition of Anaphylaxis

No universally accepted definition exists because anaphylaxis comprises a variety of features, but a good working definition is “anaphylaxis is a severe life threatening, generalised or systemic hypersensitivity reaction”, (Resuscitation Council UK 2008, Emergency treatment of anaphylactic reactions Guidelines for healthcare providers)

An anaphylactic reaction is an acute, life threatening reaction caused by the body’s reaction to an abnormal antigen/antibody; this can include any drugs or other substances including but not limited to Latex, foods and insect stings.

An anaphylactic reaction is characterised by rapidly developing life-threatening airway and/or breathing difficulty (which may be due to laryngeal oedema or asthma with shortness of breath, wheeze, tight chest, bronchospasm) and/or circulation problems usually associated with skin and mucosal changes (which can present as fainting, collapse or loss of consciousness). (Resuscitation Council UK 2008, Emergency treatment of anaphylactic reactions Guidelines for healthcare providers).

What Causes Anaphylaxis?

Nearly all drugs, including cytotoxic could theoretically produce a hypersensitivity reaction and in fact many of them have on an individual patient basis. Only a relatively select group produce significant numbers of reactions 5 – 15% and even fewer could be said to have hypersensitivity related toxicity, such that they required pre-medication, test dosing or discontinuation of therapy if they occur.

Anaphylaxis is caused by an extreme sensitivity to an allergen. The most common allergens which cause anaphylaxis are:

• Drugs, blood products, vaccines, hyposensitizing (allergen) preparations, local anaesthetics, antibiotics, aspirin and other non-steroidal anti-inflammatory drugs (NSAID), iron injections.
• Heparin and neuromuscular blocking drugs. In the case of medication, Anaphylaxis is more likely after parenteral administration. The insertion of intrauterine contraceptive device (IUCD) is also a recognised risk.
• Insect bites and stings.
• Food, eggs, fish, cow’s milk protein, peanuts and other nuts may also precipitate anaphylaxis. Be aware that some drugs use extracts from foods that may precipitate anaphylaxis e.g. arachis oil and sesame oil.
• Natural proteins or the chemical additives found in latex products may also precipitate allergic reactions.
• Substances involved in the manufacturing of food and medicines.

(anaphylaxis campaign, 2015, http://www.anaphylaxis.org.uk/hcp/what-is-anaphylaxis/signs-and-symptoms/)

Signs and Symptoms

• Generalised flushing of the skin
• Nettle rash (hives) anywhere on the body
• Sense of impending doom
• Swelling of throat and mouth
• Difficulty in swallowing or speaking
• Alterations in heart rate
• Severe asthma
• Abdominal pain, nausea and vomiting
• Sudden feeling of weakness (drop in blood pressure)
• Collapse and unconsciousness
• The patient may be able to give a history of previous anaphylaxis

A patient would not necessarily experience all of these symptoms in the same episode. (Anaphylaxis campaign, 2015, http://www.anaphylaxis.org.uk/hcp/what-is-anaphylaxis/signs-and-symptoms/)

Recognition

Allergic reactions may be local or systemic or both. Local reactions, such as those following an insect bite, are usually swelling, redness and itching. As a local reaction becomes systemic, the patient may initially complain of any of the following:

• A red rash and itching
• Feeling hot
• Anxiety
• Weakness and giddiness
• Breathing difficulties

These signs and symptoms are not entirely specific for an anaphylactic reaction; however, certain combinations of signs and symptoms make the diagnosis of an anaphylactic reaction more likely. As the diagnosis of Anaphylaxis is not always obvious, all those who treat Anaphylaxis must have a systematic approach to the sick patient. In general, treatment of an anaphylactic reaction should be based on general life support principles; the clinical signs of critical illness are similar whatever the underlying process because they reflect failing respiratory, cardiovascular and neurological systems.

Use an ‘ABCDE’ approach to recognise and treat an anaphylactic reaction. Treat life threatening problems as you find them. The principles of treatment are the same for all age groups.