Follow-up treatment
Adrenaline is critical in the immediate treatment of anaphylaxis, but patients may need additional treatment to counteract biphasic reactions or to support cardiorespiratory status. Cardiopulmonary resuscitation, oxygen, bronchodilators, steroids, and intravenous fluids may also be needed to treat anaphylaxis.
Patients must be made aware of the importance of contacting the emergency services immediately after administration of adrenaline, so that they can be observed by healthcare professionals and receive appropriate continuing care. Follow-up treatment options include:
1. Antihistamines
H1-antihistamine play an important role in managing urticaria, but should not be substituted for adrenaline as they are not useful for the initial management of anaphylaxis. Any rapid improvement seen after ingestion may be coincidental to spontaneous resolution of anaphylaxis. Antihistamines have a relatively slow onset of action (1 to 3 hours) and lack of effect on respiratory obstruction, hypotension and shock.14,15 However, they may be helpful once the patient stabilises. There is also concern about the sedative/cognitive side-effects of antihistamines.
H2 antihistamines may also be useful when given with H1 antihistamines as they can help decrease flushing, headache and other symptoms, but are not widely recommended.15
2. Corticosteroids
These are often administered to control the risk of recurring (biphasic) or protracted anaphylaxis as they have a slow onset of action (several hours). A Cochrane review raised concerns that these agents are often used inappropriately as first-line medications instead of adrenaline.42
3. ß2 agonists
If bronchospasm is persistent following adrenaline injection, nebulised ß2 agonists are useful. They are not suitable first line agents as they have no vasoconstrictor activity and so do not reduce mucosal oedema, respiratory obstruction, hypotension or shock.14
4. Vasopressors and inotropes
In patients experiencing hypotension or shock following initial treatment, positive inotropes such as dopamine and dobutamine that stimulate the heart may be effective, as are vasopressor agents that increase blood pressure, e.g., noradrenaline, phenylephrine, vasopressin.15
5. Supplemental oxygen
Supplemental oxygen is administered to make up for lack of oxygen due to restricted breathing.15,25
6. Intravenous fluids
Large amounts of IV fluids may be needed to treat hypotension and compensate for the massive loss of intravascular fluids caused by increased vascular permeability and vasodilation during anaphylaxis.15,41
7. Immunotherapy
Patients with allergic rhinitis, asthma, or insect venom allergy may also receive immunotherapy (desensitisation). While immunotherapy is not yet routinely done for food allergies, it is an emerging field.
The goal of immunotherapy is to make the allergic individual tolerant to the allergen(s) in question by regular exposure to minute amounts of the allergic trigger and increasing the dose over time. Immunotherapy has many effects on the immune system, but one of its effects is to stimulate the production of antibody classes other than IgE. The increased presence of other antibody classes serves both to decrease the amount of allergen-specific IgE and to compete with existing IgE for binding to allergens. Immunotherapy can be associated with systemic allergic reactions.43, 44
- 14 - Simons FER. J Allergy Clin Immunol 2010;125:S161-81.
- 15 - Simons FER et al. J Allergy Clin Immunol 2011; 127(3):587-93.
- 25 - Resuscitation Council (UK) Guidelines. January 2008. Available at: www.resus.org.uk/pages/reaction.pdf Accessed on 03 June 2011.
- 41 - EpiPen Summary of Product Characteristics, MEDA Pharmaceutical Ltd, April 2011.
- 42 - Choo KJL et al. Glucocorticoids for the treatment of anaphylaxis: Cochrane systematic review. Allergy 2010;65:1205–11.
- 43 - Frew AJ. BMJ 1993;307:919-23.
- 44 - Ozdemir C et al. Allergy Asthma Clin Immunol 2008; 4(3), 2008: 106–110.