Wilderness and Rescue Medicine 8th Edition

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Section III: Critical System Problems and Treatment

Anaphylaxis

Signs and Symptoms: • Generalized and facial hives • Tight or scratchy throat • Vascular and volume shock • Respiratory distress • Nausea, vomiting, diarrhea • Altered mental status

Low Risk

High Risk

Hives on the abdomen of a patient with anaphy- laxis, prior to the administration of epinephrine. Epinephrine is supplied as a liquid specifically for the treatment of anaphylaxis in the form of a pre-loaded autoinjector such as an EpiPen that automatically injects the specified dose when pressed firmly against the skin. In the United States, these devices are available only by prescription. Patients known to have severe allergies often carry one. Many other countries like Canada and Mexico allow autoinjector sales without prescription.

A previous history of anaphylaxis is not neces- sary to make the diagnosis. A significant percent- age of patients presenting with anaphylaxis will have no known history of allergy. In the remote setting, early and aggressive treatment for evolv-

ing anaphylaxis is always warranted. Treatment of Anaphylaxis

BLS and PROP is appropriate, but not definitive. Specific treatment with epinephrine is required to immediately reverse the systemic response. The Wilderness Protocol for anaphylaxis adds the use of oral antihistamines and steroids which may help prevent the reoccurrence of the problem. The recognition of anaphylaxis and the use of these medications are important skills for the wilder- ness medical practitioner. Epinephrine (adrenaline) is a potent vasocon- strictor and bronchodilator that also helps to stabilize the activated mast cells, reducing the release of histamine and other mediators. It is most effective when injected into the muscle of the lateral aspect of the thigh. The standard adult dose is 0.3 mg. The patient’s symptoms usually improve within 90 seconds. Repeat doses may be necessary if symptoms do not improve or if a rebound (biphasic) reaction occurs.

Anaphylaxis Treatment

Epinephrine: • Inject 0.3mg (0.3ml) by intramuscular injection (IM) into lateral mid-thigh. • Repeat as soon as 5 minutes if needed . • Action: bronchodilation, vasoconstriction, stabilizes mast cells . WILDERNESS PROTOCOL Antihistamine : • 10mg cetirizine or 50mg diphenhydramine by mouth. • Action: blocks histamine at receptor sites . Corticosteroid : • 10mg dexamethasone or 60mg prednisone by mouth. • Action: anti-inflammatory, may help prevent biphasic reaction .