“Anaphylactic shock”
More and more these days barn and horse owners alike are doing their own vaccinations as well as treating their horses for illness or injury in a manner that requires they administer topical, oral and injectable medications. It’s important to know the risks involved in treating your own horse as well as symptoms and emergency treatment in the event your horse has an adverse reaction.
Anaphylactic Shock is an acute hypersensitivity reaction. It develops in a horse after being exposed to an allergen that it is highly sensitive to. Penicillin antibiotics, vaccines, and immune serums are allergens most frequently involved in anaphylactic shock. Anaphylaxis is generalized (systemic) or localized. A localized reaction, such as an insect bite can consist solely of itching and swelling around bite site. With systemic reactions, the symptoms become generalized, often appearing elsewhere on the body. A severe systemic anaphylactic reaction is accompanied by sweating, anxiety, difficulty breathing, diarrhea, shock, a drop in blood pressure, collapse and death. Signs are produced by histamine and other vasoactive substances which are released by basophil and mast cells in response to the allergen.
Early recognition is essential to treatment of anaphylactic shock. Difficulty breathing and sudden anxiety following a vaccination or administration of a drug are indications to treat. The antidote for anaphylactic shock is epinephrine. Mild reactions require 1-2 ml of a 1:1000 epinephrine solution given intramuscularly or subcutaneously. Life-threatening reactions require administering 4-8 ml of 1:1000 epinephrine solutions intramuscularly or subcutaneously or 3-5 ml of 1:10000 solutions intravenously via the jugular vein over a 3-5 minute period. Epinephrine should be repeated every 15 minutes as necessary and if time permits a permanent IV line should be established as further medications and large volumes of fluid may be needed to aid circulation.
Dexamethasone, a corticosteroid (0.1 mg per pound) is frequently administered for it’s anti-allergic effects. An antihistamine like pyrilamin maleate dosed at 0.5mg per pound by intramuscular or intravenous injection is often sufficient for a mile local reaction and helpful in a severe reaction to complement the above medications.
As a precaution, it is advised not to administer any drug or vaccine which has produced an allergic reaction in the past, including hives. All facilities which routinely give injections should have Drugs used for anaphylactic shock available in their medical supplies.
Source: Horse Owners Veterinary Handbook, by James M. Giffen, M.D. and Tom Gore, D.V.M.