How to treat anaphylactic shock in cats

What Is Anaphylaxis?

Anaphylaxis is a sudden and violent allergic reaction to a foreign compound that has been introduced into your pet's body. It is a more severe form of a slower but similar phenomenon, common allergy. Common allergies in your pet appear much slower and take the form of a rash and itching, respiratory congestion or vomiting and diarrhea.

An allergen, is any substance that causes either reaction. Most allergens are complex proteins. They are substances that the immune systems of a few pets and people recognize as "foreign" or "dangerous" but which cause no response in the majority of pets and people. An anaphylactic allergen can be a drug, an insect sting, a food ingredient, a vaccine component, any injected product containing large molecules or an ingredient in cosmetics.

Allergens cause the body to produce antibodies (immunoglobulins of the E class (IgE)). These IgE antibodies are bound or joined to cells in your pet's blood called basophils and to tissue cells called mast cells. They cause both these cells to release powerful chemicals when they come in contact with an allergen they have "met" before. The chemicals these cells produce, cause negative changes in your pet's heart function, blood pressure, blood vesicle permeability as well as injury to surrounding tissue. These are the visible signs of anaphylaxis. There are two forms of anaphylaxis: true anaphylactic reaction and anaphylactoid (anaphylactic-like) reactions. Clinically, it is difficult to distinguish between the two.

How It Works:

When mast cells living in the connective tissue are damaged, they secrete heparin and histamines. Histamine is an important chemical in causing the changes associated with anaphylaxis and inflammation. When your petâ€[emoji]8482[/emoji]s body is exposed to an allergen the first time, itâ€[emoji]8482[/emoji]s body produces IgE antibodies that stick to these mast cells. When your pet is exposed to the allergen a second time, at some later date (even years later), the mast cells disintegrate, liberating heparin and histamines. Anaphylactoid reactions are identical to anaphylactic reactions in terms of clinical symptoms. However, anaphylactoid reactions are the result of non-immunological factors, which directly stimulate the mast cells. Unlike anaphylasis, anaphylactoid reactions do not require a multiple exposures. A single exposure to the foreign agent can result in anaphylactoid symptoms. In both conditions, activation of mast cell histamine results in a number of physiological changes affecting respiration and circulation, which often cause life-threatening emergencies.

Symptoms of Anaphylaxis In Your Pet:

The symptoms of anaphylaxis will occur in your pet within one hour of exposure to the allergen. The most common form I see in my practice is anaphylaxis brought on by a booster vaccination. These reactions occur very rapidly – usually within thirty seconds. Many of the vaccine reactions that owners report to me do not meet the time factor or symptomatology of true anaphylaxis. I suspect that many of these reactions are at least partially psychological in nature because they usually occur in fearful or high-strung pets. This doesnâ€[emoji]8482[/emoji]t mean they are not real. Fear causes the release of many physiological mediator chemicals that make drug reactions more likely. In mild cases, the only signs are low fevers, sluggishness and loss of appetite. Pets that develop a mild first case often go on to develop more severe cases during subsequent exposure to the allergen. In addition to these signs, moderate cases often develop urticaria, which is also called “goose bumps†hives or wheals. These raised patches develop over the head and trunk. Urticaria is a more common sign in dogs than in cats or ferrets. In anaphylaxis, the lips of dogs and cats may also become reddened and puffy. With time, areas of urticaria usually become intensely itchy and later peel like a sunburn.

If your pet is experiencing a severe case of anaphylaxis, the first sign will be a rapid drop in blood pressure. This causes its gums to become pale and it's breathing to become rapid and difficult. The pet often urinates, defecates and vomits in response to the histamine release. The pet's heartbeat is often rapid, weak, or irregular and they often appear uncoordinated, restless and frightened. Bloody diarrhea or dark stools may follow. When swelling of the larynx occurs these pets can die due to their inability to breathe. In the most severe cases, shock, collapse, convulsions and coma, can occur. Sometimes the petâ€[emoji]8482[/emoji]s temperature falls to subnormal while others they run fevers.

How We Treat Anaphylaxis:

What You Can Do:

Get your pet to a veterinarian as quickly as possible. Get someone else to drive you. On the way, stroke and reassure your pet and try to keep it calm. Place it on a blanket on its side with its rear legs slightly elevated. Loosen its collar. If it feels chilled, cover it. Do not give it anything by mouth - including water. If it stops breathing, begin CPR.

What Your Veterinarian Will Do:

Severe anaphylaxis is a veterinary emergency. Do not take a seat in the waiting room - ask that the veterinarian see your pet immediately. Call ahead to alert them if you can. If the pet is having difficulty breathing through its swollen larynx, the veterinarian will insert a tube into its windpipe. A drop in blood pressure and circulatory collapse starve the body of oxygen. This can be usually be corrected by putting the pet in an oxygen-rich environment. The liver and intestines are particularly affected in anaphylaxis. Capillary blood vesicles throughout the body become more permeable and leak blood serum into the tissues. To counteract this, intravenous fluids are usually given rapidly and in large quantities. These pets will be closely monitored so as not to over-flood their lungs with fluid (pulmonary edema). Salt solutions and fluids such as Ringerâ€[emoji]8482[/emoji]s solution are often given to counteract circulatory collapse. Urination is a good sign that fluids are working. Colloidal fluids such as polysaccharide, dextran or hetastarch, are preferable to saline solutions because they do not leave the circulation (leak out) as rapidly as Ringerâ€[emoji]8482[/emoji]s solutions and some advanced centers will use them. Many of these pets receive injections of epinephrine . This compound, normally produced by the adrenal gland, increases heart rate and blood pressure and slows mast cell disintegration. Oxygen therapy can also be very helpful, as can the intravenous administration of rapid-acting steroids such as prednisolone sodium succinate (SoluDeltaCortef) or dexamethasone sodium phosphate (Decadron). At the same time the pet may receive an injection of antihistamine (chlorpheniramine maleate, Chlor-Trimeton) or diphenhydramine (Benadryl). Pets that are hypothermic (low body temperature) are given warmth. Pets with a body temperature above 105F are rubbed down with iced water or chilled towels. Often, the pet is given an injection of a penicillin-like antibiotics to prevent secondary infections related to increased intestinal and pulmonary leakage.

Complications Of Anaphylaxis:

Sometimes nothing a veterinarian can do will stop the cascade of events that make up an anaphylactic episode. If this cascade can not be stopped, the pet will die or be left irreparably damaged. The liver suffers greatly during anaphylactic shock. It is the primary“shock-affected organ†in the body. This is because liver cells are very sensitive to oxygen deprivation. When the pet's stomach and intestines do not receive enough oxygen during an anaphylactic crisis, their cells may die leading to fatal ulcers. These pets may vomit bloody mucous and/or pass blood in their stools. In some cases bacteria gain access to the abdominal cavity (peritonitis) through these ulcerated areas. In some cases entire segments of the intestine die. Another result of anaphylaxis can be a condition called disseminated intravascular coagulation (DIC). In this condition, pooled blood coagulates within the vessels of the circulatory system leading to a deficiency in platelets. Without sufficient platelets, hemorrhages occur throughout the body. This can also be fatal.

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