Anesthesia is defined as the loss of sensation due to medication. The medication used helps produce loss of both sensation and consciousness. Veterinarians need anesthesia for most surgical procedures. General anesthesia may be used for complicated surgeries, like spays or Caesarian sections. On the other hand, local anesthesia can be used for simple procedures like wound cleaning or wart removal. Injectable medication and gas are the most common types of anesthesia.

How do anesthetics work?

Gas Anesthetics

When the patient inhales, gas is mixed with oxygen in an anesthetic machine. This causes the anesthetic to reach the lung and enter the bloodstream. Two of the most common anesthetic inhalants are Isoflurane and Sevoflurane.

Injectable Medications

Injectable medications are first metabolized by the liver, where they enter the bloodstream to cause effects. The most common injectable anesthetics include barbiturates, cyclohexamines, propofol, medetomidine, ketamine and xylazine. Each type has a different mechanism of action to cause anesthesia.

What are the differences between gas and injectable anesthetics?

Anesthetic gases are not extensively metabolized by the body.  Instead, they are eliminated from the body during breathing. In contrast, injectable anesthetic medications require metabolism by the liver, which processes the chemical, and then the medication is excreted from the body through the kidneys in urine. Therefore, gas anesthetics are the best choice if the patient has underlying liver or kidney issues.

With inhalation, the depth of anesthesia can be easily adjusted by the anesthetist by adjusting the vaporizer dial. If the patient appears too light, the concentration of anesthetic delivered by the anesthetic machine to the animal can be increased by turning the dial to give more anesthesia. If the patient appears to be too deep or when anesthesia is no longer needed, the dial is turned to discontinue the gas.

With injectable anesthetic, the only way to adjust the level of anesthesia is through administering additional medication to increase anesthetic depth or by giving medication that reverses the anesthesia.

Anesthesia recovery

The way a patient recovers from anesthesia varies with each patient and also with the anesthetic agent used.  Some agents, like ketamine, can have a rough recovery period. Often, with these medications, additional medications are given in combination to increase the smoothness of recovery.  Veterinary technicians are usually responsible for monitoring patients following surgical and anesthetic procedures to make sure the recovering animal is safe.

During the recovery period, the patient is made comfortable and given pain medication. The clinic will place the pet in a comfortable area, along with warmed blankets, to ensure comfort and warmth. The patient is monitored closely to make sure it is breathing correctly and is not retching or gagging. When the patient is discharged, specific instructions will be given to help the pet owner give appropriate home care to their pet. These instructions should be followed completely to make sure the pet remains healthy.