Anesthesia And Cats
(Ponca City, OK)
Aesthetised cat - photo by pinkypigs (Flickr)
The purpose of this post is not to provide medical information on anesthesia and cats but to prompt us to think about the risks and downside in relation to the benefits.
Anesthesia in cats carries risk of death albeit very slight. In America a study1 in 1998 found that the risk of death from anesthesia was one in 1000 or 0.1 percent. When I was in a veterinary surgery in London, England about 6 months ago I was talking to a man who had brought in his elderly female cat for teeth cleaning that requires anesthetizing the cat. He was nervous because the veterinarian had told him that the risk of death was one in a hundred. This is 1 percent and ten times higher than the findings of the American study.
Would you take your cat to the veterinarian's clinic for teeth cleaning when there was a one percent chance that it would kill your cat? I see why the owner was nervous. For me the potential downside is too high in relation to this operation. The risk invalidates the benefit. I reach this conclusion too on the basis that there is likely to be a higher occurrence of injury during anesthesia. Common sense says that injury is likely to be higher than the chance of dying but what are the figures?
The internet lets us down when we want to find out some details about the chance of our cat being injured by anesthetics. You would have thought (in a better world) that the figures were readily available - but it seems not.
One study3 in America found that "Anesthetic complications, as defined, occurred in 12.0% of dogs and 10.5% of cats..." The defined complications were: hypotension, cardiac dysrhythmias, transfusions required, hypercapnea, hypoxemia. Of these hypotension occurred in a significant 8.5% of cats. Hypotension is abnormally low blood pressure. A 10% chance is one is ten. I find that worrying.
One injury that can occur is blindness. This is most likely to be caused by a lack of oxygen to the brain during anesthesia2. In one case study4 it was found that a 6-year-old castrated male domestic shorthair cat was blind following general anesthesia. Postmortem examination revealed cerebrocortical necrosis (the death of cells in the cortex of the brain) most consistent with anesthesia related hypoxia (lack of an adequate supply of oxygen).
A lack of oxygen to the brain during the operation might be due to a pre-existing problem, a problem with the cat's interaction with anesthesia or to human error during the procedure2.
These just give a flavour of the kind of things that can occur if the "operation" is relatively unimportant such as teeth cleaning. Of course teeth cleaning can be important and necessary but if a cat's teeth are being cleaned as a proactive measure and the teeth are in reasonable condition then the downside outweighs the upside in my opinion.
Lets remind ourselves that wildcats do not clean their teeth with toothbrushes! There is surely a question mark over the process. I am sure that a wildcat's teeth are designed to last the lifetime of the cat. Are the teeth of domestic cats in a worse condition than those of wildcats? Probably, yes. If they are it must be due to diet. In which case the cat food manufacturers should do more to ensure that their products match the diet of wildcats. Between cat food manufacturers and vets we are, it seems, creating an unnecessary risk of injury and death for our cat.
The bottom line is this, we should consider the risks of an operation on our cat that requires anesthetics and measure that against the nature of the operation. And in order to evaluate the risk we should ask our vet questions. The cat is the vet's client and we are its guardian and agent in a transaction with a vet. A vet will use a risk protocol to evaluate the procedure. This protocol is probably different to our gut instinct.
Some possible questions5:
- As the vet if he or she is aware of any recalls.
- Ask whether the vet is using a mixture of injectable and gas anesthetics - these are apparently better.
- Ask if your cat will have a tube down its mouth to secure the airway.
- Ask for blood work to check for pre-existing conditions.
- Ask About Monitoring Equipment.
- Ask what your cat's condition will be like after the operation during recovery.
On a slightly different note, as at 18th May 2010, in the United States, there has been a drug recall for certain lots of the commonly used drugs ketamine and butorphanol - used to control surgery-related pain5. It might be worth asking more questions. Good vets will deal with this professionally.
1. Journal of the American Animal Hospital Association by Dyson, et.al in the July/August 1998
3. Complications and mortality associated with anesthesia in dogs and cats by JS Gaynor, CI Dunlop, AE Wagner, EM Wertz, AE Golden, and WC Demme
4. Acute vision loss after general anesthesia in a cat by I. R. Jurk, M. S. Thibodeau, K. Whitney, B. C. Gilger and M. G. Davidson