The drug of choice for emergency treatment is aqueous epinephrine,
administered parenterally. Epinephrine is the pharmacologic antagonist of the action of
chemical mediators (such as histamines) on smooth muscle and other effector cells.
a. Emergency Treatment. Quickly assess the condition of the patient. If
needed, establish an airway; begin CPR; and administer oxygen, if available. If the
reaction is due to an insect sting, a constricting band should be placed above the site of
the sting. This is only feasible if the sting is on an extremity. Inject aqueous
epinephrine into the upper arm. If glottic edema is present, a cricothyrotomy may
provide an airway. If necessary, use closed-chest cardiac massage. When help is
available, utilize it. You will need as many skilled hands as possible. Sometimes
seconds can make a difference between life and death. Use good judgment in selecting
the administration route for epinephrine and other drugs.
For mild generalized symptoms, administer subcutaneously.
(2) When reaction is more severe and is getting progressively worse,
administer intramuscularly or sublingually. This is especially necessary if you are
concerned that vascular collapse will slow or stop absorption.
(3) When aqueous epinephrine is administered intravenously, it is diluted
with saline and given slowly. This is done for profound hypotension. Care must be
taken because this administration route may cause cardiac arrhythmias. If possible,
start an intravenous infusion with normal saline or D5W for an emergency route. For
insect stings, aqueous epinephrine should also be injected at the sting site.
b. Secondary Treatment. In the event that the administration of epinephrine
does not stop and reverse the antigen-antibody reaction, it may be necessary to use
other methods. Most other drugs act upon one or several specific symptoms of
anaphylaxis. Many of those which are listed may be available at the larger medical
treatment facilities, but not at field facilities.
(1) Diphenhydramine hydrochloride (Benadryl) or other antihistamines help
block systemic histamine effects. These are usually injected intramuscularly.
(2) Aminophylline is used to combat bronchospasm and asthmatic
symptoms. If the patient is responding to epinephrine, this is usually not given.
Aminophylline is administered intravenously over a period of time. Other intravenous
infusions may also be used.