Anaphylaxis is an allergic reaction that has life-endangering effects on the circulatory and respiratory systems. Anaphylaxis is an almost immediate, rapidly progressive multi-system allergic reaction to a foreign protein injected into the body by stinging and biting insects, snakes, and sea creatures or ingestion or inhalation of food, chemicals, and medications.
Early recognition and prompt treatment of anaphylaxis, particularly in a wilderness setting, is essential to preserve life. The onset of symptoms usually follows quickly after an exposure (minutes after a sting or bite, within 30-60 minutes following ingestion). Over 20% of all anaphylactic reactions are biphasic reactions, meaning the swelling of the airway can reoccur within one to 72 hours after the original attack.
Physical findings include rapid heart rate, low blood pressure, and other evidence of shock, upper airway obstruction (stridor) and lower airway obstructions (wheezes) with labored breathing, generalized skin redness, hives, and swelling of the mouth, face, and neck.
Epinephrine should only administered to patients having symptoms suggestive of an acute systemic reaction (i.e. generalized skin rash, difficulty breathing, fainting, or facial swelling).
- Maintain an open airway, assist ventilations if necessary, and put patient in a position of comfort. Initiate CPR if necessary.
- Inject 0.3 mg of 1/1000 epinephrine into the lateral thigh of an adult over 66 pounds (0.15 mg for a child, 33-66 pounds).*
- Repeat injections every 5 minutes if condition worsens or every 15 minutes if condition does not improve, for a total of up to three doses.
- Administer 50–100 mg of diphenhydramine by mouth every 4–6 hours if the patient is awake and can swallow.
- Consider Prednisone 40–60 mg / day (or equivalent dose of an oral corticosteroid).
- Because a rebound reaction can occur, all victims of an anaphylactic reaction should be evacuated. Rebound (biphasic) reactions should be treated in the same manner as the initial reaction, using epinephrine in the same dosage.
* There is 1 mg of epinephrine in 1 ml of epinephrine 1/1000; there are 0.3 mg in 0.3 ml of 1/1000. Pre-loaded commercially available injectors deliver either 0.3 mg (standard adult dose) or 0.15 mg (standard pediatric dose). If the person weighs less than 66 lbs (30 kg), the doses are: epinephrine is 0.01 mg/kg; diphenhydramine is 1mg/kg; and prednisone is 1 – 2mg/kg. When using lbs, multiply the weight times 0.45 to get the weight/mass in kilograms.