Current management of anaphylaxis

The term anaphylaxis is used to describe both IgE, immune-mediated reactions and nonallergic,

non-immunologically triggered events. Co-morbities such as asthma or

infection, exercise, alcohol or stress and concurrent medications such as beta-blockers,

angiotensin converting-enzyme inhibitors (ACEI) and aspirin increase the risk of

anaphylaxis occurring. The pathophysiology involves activated mast cells and basophils

releasing preformed, granule-associated mediators, and newly formed lipid mediators, as

well as generating cytokines and chemokines. These cause vasodilatation, increased

capillary permeability and smooth muscle contraction, and attract new cells to the area.

Positive feedback mechanisms amplify the reaction, although conversely reactions can

self-limit. Parenteral penicillin, hymenopteran stings and foods are the most common

causes of IgE, immune-mediated fatalities, with radiocontrast media, aspirin and other

non-steroidal anti-inflammatory drugs most commonly responsible for non-allergic

fatalities. Deaths are rare but do occur by hypoxia from upper airway asphyxia or severe

bronchospasm, or by profound shock from vasodilatation and extravascular fluid shift.

Oxygen, adrenaline (epinephrine) and fluids are first-line treatment. Adrenaline

(epinephrine) 0.01 mg/kg to a maximum of 0.5 mg (0.5 mL of 1:1000 adrenaline) i.m.

in the upper lateral thigh acts to reverse all the features of anaphylaxis, as well as

inhibiting further mediator release. Crystalloids such as normal saline or Hartmann’s

solution at 10-20 mL/kg are essential in shock. The role of H1 and H2 antihistamines,

steroids and glucagon is unclear. They should only be considered once cardiovascular

stability has been achieved with first-line agents. Discharge may follow observation from

four to six hours after full recovery. A clear discharge plan, and referral to an allergist for

all significant, recurrent, unavoidable or unknown stimulus reactions are essential. Patient

education is important to successful, long-term care.