Anesthetics are drugs used to block the sensation of pain. They are divided
into two categories: local anesthesia and general
Local anesthesia is used for surgery on the surface of the body, where it is
injected into tissues and around regional nerves. It may be applied topically
to mucous membranes. Local anesthetics (such as xylocaine) have the fewest
risks and side effects but are not suitable for most major surgeries.
General anesthesia renders the cat
unconscious. It can be given by injection or inhalation. Light anesthesia
sedates or relaxes the cat and may be suitable for short procedures, such as
removing a foreign body from the mouth. Inhaled gases (such as halothane,
sevoflurane, and isoflurane) are administered through a tube placed in the
Combinations of anesthesia often are used to lessen potential side effects.
For example, ketamine and xylazine (Rompun) are common injectable anesthetics
used together for short procedures. The guideline dose of an injectable
anesthetic is computed by the cat’s weight. Since cats are unusually sensitive
to ordinary doses of a drug such as barbiturates, veterinarians often
administer the anesthetic in repeated small doses until the desired affect is
obtained, rather than giving it all at once.
For gas anesthesia, the mixture of oxygen and anesthetic is balanced and the
dose adjusted according to the breathing of the cat. Many factors require that
the exact dosage be customized to the individual cat. Certain breeds have an
increased sensitivity to barbiturates and other anesthesia, and that must also
be taken into account. This may be related to structure, such as cats with
short faces, or conformation, such as thin cats without extra weight or
Anesthesia is removed from the cat’s system by the lungs, liver, and
kidneys. Impaired function of these organs can cause dose-related
complications. If your cat has a history of lung, liver, kidney, or heart
disease, the risk from anesthesia and surgery is increased. Cats with those
problems may require less anesthetic to attain the needed depth of anesthesia
or may take longer to become fully aware after anesthesia. Presurgery bloodwork
is recommended to detect any such problems. Some clinics may also suggest chest
X-rays, an EKG, and blood pressure evaluations, especially if your cat is
A major risk of a general anesthetic is the cat vomiting when going to sleep or
waking up. The vomitus refluxes into the trachea and causes asphyxiation. This
can be avoided by keeping the stomach empty for 12 hours before scheduled
surgery. If you know your cat is going to have surgery, do not give anything to
eat or drink the night before. This means picking up the water dish and keeping
the cat away from the toilet bowl and other sources of water, as well. If your
cat has liver or kidney problems, your veterinarian may suggest leaving water
available. Diabetic cats may need adjustments in their feeding schedule
and insulin injections.
Your cat will also have an endotracheal tube placed into his trachea. This
has a small balloon cuff to prevent any fluids from leaking into the lungs.
This tube is attached to the gas anesthetic machine.
WebMD Veterinary Reference from "Cat Owner's Home Veterinary Handbook"