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Created: 17/5/2006
Anaphylactic reactions are the immediate type of hypersensitivity that result from interaction of antigens with specific IgE antibodies bound to mast cells and basophils.

They involve the release of vasoactive bronchoconstrictive substances such as:

  • Histamine
  • Leukotrienes
  • Chemotactic factors

Anaphylaxis: requires an individual to be previously sensitised

Anaphylactoid: indistinguishable but require no previous exposure (IgG mediated, with complement activation).


  • Cardiovascular collapse 88%
  • Bronchospasm 36%
  • Swelling of face 24%
  • Generalised swelling 7%
  • Cutaneous signs
  • Rash 3%
  • Erythema 45%
  • Urticaria 8.5%

First observed signs

  • No pulse/ fall in BP
  • Difficulty inflating lungs
  • Flushing
  • Coughing
  • Rash
  • Desaturation
  • Cyanosis
  • Others (ECG changes, swelling, urticaria)

Primary management

  • Stop drug
  • 100% O2 and maintain airway
  • Get help
  • Lay patient flat with legs elevated
  • Give IV fluids (crystalloid or colloid)
  • Give adrenaline (IM: 0.5-1 mg every 10 mins, IV 50-100 mcg slowly over 1 min)

Secondary management

  • Antihistamines (chlorpheniramine 10-20 mg slowly IV)
  • Corticosteroids (100-300 mg hydrocortisone)
  • Catecholamine infusion
  • Bicarbonate for acidosis (0.5-1 mg/kg for acidosis)
  • Airway evaluation
  • Bronchodilators for persistent bronchospasm


  • Counselled and investigated
  • 10 ml of blood for serum tryptase associated with mast cell degranulation (measure at 1 hour and also 6-24 hours post-reaction so that the baseline tryptase level can be determined)
  • Skin prick tests may be useful
  • RAST testing: measures circulating IgE
  • Submit a yellow card
  • Information to patient and GP (?medic alert bracelet)

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