Propofol (a nonbarbiturate hypnotic), is the "injectable of choice" for certain veterinary procedures, as it is quick-acting, offers a rapid recovery period, and rarely induces drug aftereffects. Dosage for propofol, as for all licensed drugs, is governed by the FDA. However, propofol is contraindicated for cats with certain liver diseases, since it is primarily metabolized via the liver.
Ketamine,(DA) a somewhat controversial drug, has been widely used as both a pre-anesthetic drug, and in combination with other drugs, such as Acepromazine, as full anesthesia for some procedures. It is generally considered safe, although some people believe that certain breeds of cats or dogs may be at risk with its use. Ketamine is nonnarcotic and nonbarbiturate, but interestingly, is an hallucinogenic and is used by some people as a recreational drug for that purpose. Ketamine is contraindicated in cats suffering from renal (kidney) or hepatic (liver) insufficiency, and certain other conditions.
Isofluorane revolutionized veterinary anesthesia, because of its safety (particularly with older or compromised patients), rapid recovery of the patient after surgery, and the fact that it is not likely to induce nor exacerbate heart arrhythmias. Isofluorane recently lost its patent, so is becoming less expensive than newer inhalants, and is still considered the anesthetic of choice in veterinary medicine for pregnant animals (including c-sections) and for animals with heart problems. Sevoflurane is relatively new, costing about four times more than isofluorane. Halothane costs even less than Isofluorane, and is still in popular use. Both isoflurane and halothane require the use of a precision vaporizer for measuring the appropriate deliverance of anesthetic. Your veterinarian can (and should) provide information as to which anesthetics he/she uses and why.
It has been said that there is no such thing as the perfect anesthetic, and there is always potential for risk with any of them. It therefore behooves us to do our homework prior to allowing any procedure requiring anesthesia, and to insist on a pre-anesthetic blood screening. This precaution is not a guarantee by any means (for instance, Cardiomyopathy will not show up on a blood panel), but it can help your veterinarian determine what is the best anesthetic or combination of anesthetics for your cat. Certain conditions may not obviate the need for anesthesia, but other precautions such as heart monitoring and/or oxygen assistance can be added for additional safety.
Potential Hazards by Drug NameThis list is not intended to instill fear nor to cause you to micromanage your veterinarian, and is by no means all-inclusive. Instead, use it as a guideline to ask questions. Your veterinarian will be glad to ease your mind about the type of anesthetic(s) he intends to use, and why.
- Barbiturates (pentobarbital, thiopental, thiamylal, methohexital)
Potential for respiratory depression with excessive doses. Contraindicated in pregnant cats. Prolonged anesthetic recovery can also be a problem when barbiturates are used in older animals, obese animals (which require higher dosage), or other animals with compromised hepatic and renal function which decreases metabolism of the drugs.1 According to Oklahoma State University, pentobarbital is no longer used for anesthetic induction due to its prolonged rough recovery.
Potential for depressed cardiac function; compromise respiratory function, including apnea (failure to breathe and/or sudden pulmonary edema (fluid in the lungs) for cats with cardiac disease or severe debilitation. Contraindicated for cases of head trauma, or cats with kidney failure.
- Propofol (sold as PropoFlo, Rapinovet, and Dipravan) Can cause apnea when inducted quickly, and overdosage can cause cardiac arrest, however ordinarily there are minimal effects on the cardiovascular system.
Because it is not an analgesic, acepromazine is usually used in conjunction with another sedative. It is contraindicated in animals with CNS (central nervous system) lesions, and can sometimes cause hypothermia.
- Halothane (inhalant)
Cardiopulmonary depresssion, and a risk of malignant hyperthermia in some breeds/strains.1
- Isoflurane (inhalant)
Respiratory depression and cardiovascular depression.1
¹From University of Minnesota Guidelines for Anesthesia, Analgesia, and Sedation