Cornell Feline Health Center

 

The Feline Health Center


Anesthesia

Whether brief and comparatively simple (such as routine dental care) or prolonged and complicated (spaying or the repair of a broken bone, for example), virtually all feline surgical procedures require that the patient be anesthetized so that the operation can be efficiently and painlessly completed. An especially excitable or hypersensitive cat may also have to be temporarily rendered unconscious during such relatively simple and noninvasive procedures as examining its ears or changing its bandages, since it may resist treatment and demonstrate its annoyance by thrashing about and clawing at the practitioner.

“Although anesthesia is used primarily for the patient’s benefit, sometimes it’s necessary for the veterinarian’s safety as well,” explains Manuel Martin-Flores, DVM, a lecturer in anesthesiology at the Cornell University School of Veterinary Medicine. Anesthetic agents, which are administered by injection under the skin, intravenously, or by inhalation, may be either local or general, their selection depending on the nature and duration of a procedure and the origin of the potential pain.

A local anesthetic blocks the pain pathways leading to the brain from a specific area of a cat’s body, such as the mouth, a paw, or an ear. Because the sensation is blocked from being transmitted from that specific area to the brain, the patient cannot perceive it. Commonly used local anesthetic agents include lidocaine and bupivicaine. Depending on the agent, local anesthetics can be applied either by injection or, in the case of a superficial wound, topically. When a procedure requiring a local anesthetic gets underway, says Dr. Martin-Flores, the patient will first be given a mild sedative to calm it down, after which the veterinarian will administer the anesthetic drug by injecting a needle into the precise area of tissue that is to be treated. Local anesthetics are typically used for suturing or cleaning wounds or removing small tumors.

Local anesthetics can also be used to anesthetize a larger region of the body, such as the abdomen. This is done by administering an epidural injection with local anesthetics, similar to the technique used in women during labor. Epidural anesthesia can also be used to anesthetize a hind limb during a fracture repair, for example. For more complicated procedures, or if the animal is intractable, general anesthesia is used. When a general anesthetic is used, all of the pathways in the nervous system that transmit pain from its source to the brain remain intact but the stimulus is blunted because the brain is asleep and the patient will not experience the pain. The attending veterinarian and/or an anesthesiologist select the types of anesthetics and specific agents to be used depending on the patient’s age and general health; the nature of the procedure; which organs are involved; and the time required for the drugs to take effect.

In a surgical procedure requiring general anesthesia, the patient is first given an injection that will sedate it, followed a short time later by administration of the selected drug, which will make the patient fall into a deep sleep. When the cat is unconscious, a tube is inserted into its trachea to ensure that the passage to its lungs remains open and the cat receives a steady supply of oxygen while it is asleep. Then the cat is connected to a device enabling it to inhale an anesthetic gas, such as Isoflurane or Sevoflurane, throughout the operation. During the surgery, depth of anesthesia is monitored by checking the animal’s pulse, heart rate, mucus membrane color, reflexes and jaw tone. Many veterinarians use pulse oximeters to measure the oxygen content of the blood and blood pressure monitors are also commonplace. At the Cornell University Hospital for Animals (CUHA), modern monitoring equipment is used, allowing close evaluation of the cat’s vital functions while under anesthesia. The anesthetic techniques and monitoring used at CUHA are similar to those used in people when they are anesthetized.

Following the procedure, says Dr. Martin-Flores, the patient will gradually come out of its sleep and will generally be able to resume its normal activities within an hour. When fully conscious, the animal will be either discharged to its owners or, if necessary, kept at the facility for further care and monitoring. Post-operative pain medications may be prescribed, depending on the procedure, but owners should never administer aspirin, ibuprofen, Tylenol® or other over-the-counter medications without a veterinarian’s approval since these medications may be toxic to cats.

In large veterinary hospitals, the operating room personnel will likely include an anesthesia specialist, whose sole job is to monitor the unconscious patient’s stability. In local clinics, this will usually be the responsibility of a veterinary assistant who performs other tasks in the operating room as well.

Cat owners should know that all licensed veterinarians are trained and qualified to administer anesthesia. “Overall,” says Dr. Martin-Flores, “owners have very little to worry about. With the development of newer, safer anesthetics and better monitoring tools, anesthesia is, generally speaking, a very safe procedure.”

By Tom Ewing
December 20, 2010