>Linda.. I'm sorry to hear you lost a horse. I've heard several stories
>like this. So... I can't stand it and am posting this to the list.
>
>I know we have a few vets on this list and I'm not one of them, so please
>join in!
>
>Every situation is different, but I have enough experience to think that
>general anesthesia and endurance horses is a special case. I'm hoping that
>this never happens to anyones horse! In a nutshell, general anesthesia
>is metabolized first into fat tissue and then it is slowly filtered out of
>the body... like in the urine.
Actually, inhalation anesthetics are primarily eliminated via the
respiratory system.
When a horse (or any animal) comes out of a
>general anthesia, the drug is still in their body, it's just moved from the
>blood stream and into the fat. The horse wakes up.
>
>Interestingly enough, I heard this from Becky Hart years ago after she bought
>her Irish Wolfhound, Baru. When he went in to get 'fixed' she mentioned that
>the vet *had* to be experienced with site hounds --> *because they have about
>1/2 the body fat of regular dog breeds*. This means they can only take about
>1/2 the general anesthesia of, say, a collie pup of the same age. If the body
>does not have enough fat tissue to absorb the drug, then the drug level in the
>blood stream can rise to dangerous levels and the animal just does not wake up.
This is more true of the barbiturate induction agents than it is of
the gaseous agents, though they have to be monitored carefully as well.
>Please tell me your vets *know* this. Endurance horses have a lower percentage
>of body fat than, say, a pleasure quarter horse. I have heard of too many of
>our friends (one was too many) just not ever coming out of general anesthesia.
>Is it related to the lower body fat? If so, do your vets realize this?
It is tricky to put any horse under general anesthesia. These
animals are large, and the physics of recumbency pose problems aside from
the drugs used. Lungs consolidate; myopathies develop, simply because the
horse was not created to lie on his back for any length of time.
>
>:( - kat
>kmyers@collagen.com
>
>
I missed Linda's original post about the anesthesia, but, in my
experience, *any* anesthetized horse is monitored *very* carefully. Arterial
blood pressure and blood gases, the whole nine yards. Anesthesia is kept as
light as possible, and I've even heard an anesthesiologist tell the surgeon
that he had 10 minutes to finish up, because the horse had been under long
enough!
Keep in mind also, that a fair number of horses who go under for
surgery are TB's from the track, and a fit racehorse isn't carrying any
excess fat, either. I sincerely doubt that this is anywhere near as much of
an issue with horses as it is with small animals. (BTW, I would uspect a
collie pup to be fairly sensitive to anesthesia as well.)
Also, isoflurane, a newer gas, is not absorbed by fat to any great
extent. It is a great deal more expensive than
halothane, and recovery is sometimes rougher, but the most important
component of any anesthesia, IMHO, is the person handling it.
--C.M.Newell, DVM
"The expression in a horse's eye is like a blessing on a good man's house."
--Sayied iben-el Rabil, quoting the Prophet