hi i have a good resorce...
Time and time again we hear of people whose vets (or vet's receptionist) have requested they fast their rabbit the night before a procedure involving a general aneasthetic is carried out. This is incorrect and dangerous advice which needs to be corrected amongst rabbit keepers as it is putting lives at risk. If your vet recommends starving your rabbit prior to a GA procedure it indicates a general lack of understanding about the physiology of a rabbit on the vets part and therefore suggests they may not be sufficiently experienced to treat your rabbit correctly. Always ask about a vets pre-operative policy before registering your rabbit with them. It could save your bunnies life.
The reason most animals and people are fasted before surgery is to prevent them vomiting under GA, and then inhalating and/or choking on their own sick whilst unconscious. Rabbits, however, are unable to vomit (as are horses) because they have a highly developed cardiac sphincter which means they do not have a 'gag' reflex and are unable to regurgitate in any form.
Some veterinarians try to fast rabbits because they feel ingesta sitting in the intestines will interfere with the rabbits weight and therefore affect the amount of aneasthetic and other drugs they require. However a rabbit takes approximately 12 hours from consuming food to passing it, which means the rabbit would have to be starved for 12 hours plus before surgery to get a true weight. Furthermore, the rabbit's ceacum (where ceacal pellets are formed) can take up to 4 days to fully empty and fasting for that lenght of time would be fatal. Given how long it takes a rabbits intestines to process food it would be impossible for the GI tract to empty during the period the rabbit is in surgery if it has been eating as normal immediately prior to the procedure, and therefore it's weight should hardly be affected. Many vets choose to use safer Isoflurane gas as opposed to injectable aneasthetics and in this situation body weight is irrelevant, as the drug enters the body through the respiratory system.
Rabbits have a very complex digestive system which focuses around the gastro-intestinal tract. The GI tract is designed to be in constant use with food always passing though it, this is referred to as GI motility. At no point should it ever be allowed to empty as this can lead to it beginning to slow and then shut down. Once the GI tract has begun to enter Stasis (immobility) it is a difficult task to restore gut motility and can lead to the rabbit becoming critically ill. Fluid and fiber are vital for keeping the GI tract running, if a rabbit is deprived of these through fasting then gastro-intestinal stasis developes.
A general aneasthetic will automatically slow down a rabbits digestive system and if the GI tract is already empty (and therefore less mobile) on top of this the chance of getting motility back up to speed after the procedure is dramatically reduced. Vets should always offer a gut stimulant such as metaclopromide post-op to encourage the GI tract to remain mobile and also as an appetite stimulant . It is just as virtal that a rabbit who has undergone an operation or painful procedure be given an analgesic as a rabbit's primary response to pain is to stop eating, further impacting on gut motility.
If your rabbit is not eating voluntarily or passing stools within 24 hours post-GA consult your vet for further advice. Anorexia in rabbits can quickly cause liver damage so it is very important that your rabbit receives every support in keeping his GI tract running smoothly.
References
Pre & Post Operative Care by Dana Krempels
Medical Concerns HRS by the House Rabbit Society
