Wilderness and Rescue Medicine 7th Edition Jeffrey Isaac, PA-C and David E. Johnson, MD

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Wilderness and Rescue Medicine

evacuation. Practitioners trained and comfortable with syringes and ampoules or vials may choose to carry epinephrine in that more economical and compact form. Epinephrine should be protected from light, freezing, and excessive heat. The epinephrine injection is often followed by an antihistamine, a type of drug that is believed to directly block the attachment of the hista- mine molecule to receptor sites on body tissues. Diphenhydramine is a common example. It takes effect in about 15–20 minutes. Neither epinephrine nor diphenhydramine will remove the antigen or the histamine. It is possible to see a biphasic reaction with the reappearance of symptoms minutes to hours later. Because the effects of epinephrine are temporary, evacuation and medical follow-up should be planned. For offshore situations or long evacuations, add- ing prednisone at a dose of 40 - 60 mg once a day may suppress the inflammatory response associ- ated with the reaction. This will make a biphasic reaction less likely. Prednisone can be used at this dose for up to 5 days.

the drugs and dosages prescribed by the protocol are highly unlikely to produce an adverse out- come, even if the problem is misdiagnosed and the treatment turns out to be unnecessary.

General Principles

Anaphylaxis Wilderness Perspective

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High Risk Problem: • Persistent abnormal mental status • Incomplete response to treatment • The patient is getting worse • Second injection of epi is needed

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The greatest direct risk would be in giving epi- nephrine to a patient who is suffering a heart attack. Fortunately, the signs, symptoms, and mechanism are markedly different and unlikely to be confused with anaphylaxis. The most com- mon problem to be mistaken for anaphylaxis in the field is acute stress reaction following multiple wasp or bee stings. In any case, once you have initiated emergency treatment with epinephrine, evacuation for medi- cal follow-up is ideal. If the patient has recov- ered from the event, it need not be an emergency. However, a history of previous hospitalization for anaphylaxis or failure to improve to normal after the first injection indicates a higher risk patient. In remote or dangerous circumstances where evacuation is not safe or practical, continued use of the diphenhydramine every 4 to 6 hours may be advisable for several days. Continuing the pred- nisone once a day may also help prevent biphasic reactions and is safe for treatment up to 5 days. Careful monitoring is crucial.

The patient in the photograph on the previous page approximately 12 minutes after the administration of epinephrine and diphenhydramine.

Risk Versus Benefit The emergency field treatment of anaphylaxis is a low-risk solution to a high-risk problem. You have a much better chance of saving a life with an injec- tion of epinephrine than almost any other piece of medical equipment you can carry. Furthermore,