What Is Used to Put Cats to Sleep During Spaying?

Veterinarians rely on several different classes of medications when preparing a kitty for a spay surgery. The American Animal Hospital Association, in its AAHA Anesthesia Guidelines for Dogs and Cats, recommends vets use a pre-anesthetic sedative to decrease stress in the patient and facilitate easier handling of a fearful cat. These sedatives include benzodiazepines, acepromazine and opiate agonists. Ketamine is also often used to quiet nervous cats. These medications are sometimes used in combinations with the anesthetics being employed during the spay surgery. Kitty cocktails such as these do carry some risks—all anesthetics do—but overall are considered safe and are widely used.

General anesthesia is used to help put the patient to sleep, block pain and temporarily paralyze the animal to reduce movement during surgery. The barbiturate thiopental is sometimes used to induce general anesthesia. Other injectable drugs used for uncomplicated spay procedures include ketamine and Telazol, although ketamine does not paralyze the animal. These are in a class of drugs referred to as dissociative drugs. If you were to look in on a spay surgery on a cat under one of these drugs, you might be horrified to see the cat's eyes open; in the case of ketamine, there might even be movement. However, the cat is unaware of what is going on around her, cannot feel anything and won't remember anything about the experience. These drugs can be given as needed throughout the surgery.

Another type of anesthesia veterinarians use for spay surgeries are inhalation, or gas, anesthetics. First, a dissociative drug is administered to quiet the cat and make her easier to handle. Then a mask is placed over her fuzzy face and she breathes in a mixture of gas and oxygen. The two most commonly used gases are isoflurane and halothane. These drugs can be administered through a trachea tube as well, and this method is sometimes preferred over the gas mask because it hastens induction and reduces the chances of anyone but the cat getting a dose of gas. Both of these gasses are quickly eliminated through breathing, so they must be provided and monitored throughout the spay surgery.

In the case of feral cats, who are notoriously difficult to handle and medicate, Alley Cat Allies, a feral cat advocacy organization, recommends a cocktail known as TKX—Telazol, ketamine, and xylazine—given as an intramuscular injection. These drugs contain analgesic, dissociative and muscle relaxant properties and wear off in about 30 minutes, but if the cat is having trouble coming out of the anesthesia, a drug that reverses the effects of TKX, yohimbine, is administered.

Since new anesthetic drugs and/or protocols are evolving all the time, it's imperative your vet participates in opportunities for continuing education. After all, there was a time when vets thought cats didn't feel pain at all. Now look how far they've come.