Veterinary anesthesia is used to induce a state of unconsciousness in an animal. It is used during veterinary surgery, and is often required for diagnostic procedures since animals usually won’t remain still long enough for certain tests to be performed. The drugs used for veterinary anesthesia are usually inhalants or injections, and the anesthetics used on animals are the same drugs used on humans.
An anesthetic serves three main purposes: immobilization, unconsciousness, and analgesia or pain relief. Some drugs can provide all of these effects when used alone, but a combination of drugs is frequently used in veterinary anesthesia. Sedatives may be used to immobilize the animal, an analgesic is employed to relieve pain, and another drug may be administered to induce unconsciousness. A common combination is the use of opiates and tranquilizers to sedate an animal before a state of general anesthesia is induced. Opiates won’t bring about a state of unconsciousness in an animal, but they are used for pain relief, while the tranquilizers will relax and calm the animal.
Guaifenesin is sold over the counter as an expectorant for people, and it is used in veterinary medicine to relax the animal before a general anesthetic is administered. Ketamine is often used as an anesthetic for both children and animals. It is frequently used in combination with midazolam or diazepam for veterinary anesthesia, both of which are also used to sedate humans. Morphine is another drug commonly used for sedation in both humans and animals.
Barbiturates are frequently used in veterinary anesthesia to induce short term unconsciousness. Thiopental is the most-commonly used barbiturate for this stage of anesthesia but other, non-barbiturate drugs have also gained popularity for anesthetic purposes. Propofol, when administered intravenously, provides a quick onset of unconsciousness but has no effect on pain, so it must be used in conjunction with an analgesic. Since drugs in combination often have a synergistic effect, the dosages can be much smaller than when each drug is used alone.
Anesthetics affect different species in different ways, so a drug that will be safe and effective on one type of animal may be harmful to another. For example, morphine is frequently used to sedate dogs, but when administered to a horse may cause mania. Midazolam will sedate guinea pigs and rabbits, but it has the opposite effect on cats and dogs, inducing a state of excitement. A veterinarian may encounter a variety of species in his or her practice, and must have the knowledge of the effect the different veterinary anesthesia drugs may have on each patient.