Anaphylaxis: A Detailed Review

This article reviewed anaphylaxis causes, diagnosis, treatment, and prognosis in detail, focusing on dogs and cats but also reviewing human literature. Anaphylaxis is a sudden, acute systemic allergic reaction. In dogs and cats, the most common causes are insect and reptile venom, antimicrobial agents, NSAIDs, opiates, vaccines, blood-based products, radio-contrast agents, food, and physical factors such as cold and exercise.

Anaphylaxis is diagnosed via patient history and clinical signs. When triggered, anaphylaxis causes a massive histamine release in the skin, liver, lungs, and GI tract. In dogs, the GI tract and liver are primarily affected; in cats, the respiratory system is primarily affected. Histamine, along with other inflammatory mediators, increases vascular permeability and smooth muscle contraction.

The mainstay of anaphylaxis treatment is epinephrine. Epinephrine is a vasopressor that will improve cardiovascular status. Use of a continuous epinephrine infusion as opposed to a single injection may prove beneficial. IV fluid therapy, H1 and H2 antihistamines, corticosteroids, and bronchodilators also improve cardiovascular function in anaphylactic patients. A biphasic reaction is possible. Prognosis can vary greatly—from death to full recovery. Cases with the most severe reactions often happen when parenteral antigen exposure occurs.

Commentary

Ever had a patient present with clinical signs of shock or death without having a history of illness? Or seen a small-animal patient develop cardiovascular collapse at the end of an IV injection of dexamethasone, or just die after a slow IV injection of cephalexin? I have, and there continues to be little information on the clinical syndrome of anaphylaxis in small-animal patients, particularly cats. Our standard of care (ie, epinephrine IM, dexamethasone, antihistamines) may not even be useful for acute anaphylaxis.—Elke Rudloff, DVM, DACVECC

Source

Anaphylaxis in dogs and cats. Shmuel DL, Cortes Y. JVECC 23:377-394, 2013.