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For healthy adult dogs about to undergo an operation, the American Animal Hospital Association now recommends a 4- to 6-hour fast prior to anesthesia. The organization suggests even shorter pre-surgical fasts for dogs younger than 2 months of age and dogs with diabetes, who need to eat their food at specific times to pair with their insulin injections. Yet a common veterinary practice is for clinics to tell their clients, “no food after midnight” (although water is always okay). That means if the surgery is going to take place later than noon, the dog will have to wait longer than 12 hours to eat. Why do so many veterinary clinics advise “nothing-after-midnight” when the latest guidelines do not square with that advice?
French and English bulldogs have an extremely high incidence of hiatal hernia — a case of the stomach popping through the diaphragm and into the chest cavity. That predisposes them to chronic regurgitation of stomach contents, making their anesthesia risk “pretty high,” says Tufts veterinary anesthesiologist Alicia Karas, DVM. For that reason, these breeds are watched especially carefully at Tufts while under anesthesia, with guidelines in place to make sure they remain safe during an operation.
And because dogs with diabetes can’t go too long without food, they are always taken first for operations (and their owners are told to inject only half their usual insulin the morning of the operation).
Different breeds and different health conditions often translate to protocols being tweaked to help insure a dog’s health while she is anesthetized.
The whys and wherefores of anesthesia protocols
The reason dogs have to fast before anesthesia at all is that stomach contents can be vomited up to the mouth while a dog is unconscious under the anesthetic drugs and then migrate down the trachea and, from there, to the lungs. That sometimes leads to aspiration pneumonia, which can be deadly. Stomach contents can also be regurgitated into the esophagus, which may result in a stricture, or narrowing, that heals with significant scar tissue, meaning food can’t easily pass. If the esophagus can’t be ballooned open, the dog may have to be fed with a stomach tube for life. Such complications are rare, but they do occur.
Research indicates most dogs are safe from stomach contents going to the wrong places after just 6 hours of fasting before anesthesia induction, but protocols are slow to change. “It always takes a while for new guidelines to percolate into actual practice,” says Tufts veterinary anesthesiologist Alicia Karas, DVM.
There’s more to it than that, however. In a number of veterinary practices, particularly large ones, it’s virtually impossible to say exactly what time a planned surgery will occur. “It’s very difficult to schedule OR [operating room] time,” Dr. Karas says. “We have a pretty good idea how long an operation will last,” she explains, “but there are complications. It’s not like they’re all easy spays and neuters. Timing can be thrown off tremendously even by something like not being able to get an IV line into a dog. We had one dog recently — every vein was ruined by anti-seizure meds. So his surgery was held up.
“Or a surgeon comes in and is supposed to do two knee surgeries and one bladder surgery. But there’s an emergency. A dog swallowed a skewer, and it’s poking through his stomach. That can’t wait. Or something is bleeding into a dog’s abdomen. So all of a sudden the knee the surgeon was going to do starting at 8:30 is pushed off, and then we actually have no idea of who’s going to go when. Some dogs may be pushed up while others are pushed back. A bomb is dropped into the schedule almost every day.”
The toll fasting takes
It’s hard for dog “parents” to see their pets go hungry after more than 12 hours of not eating, with the animal not understanding why she can’t get breakfast the morning of the surgery, and not even understanding that she’s going for surgery. But it’s often not as bad as it may seem, Dr. Karas says. “Let’s say you feed your dog at 6 pm, which many people do,” she comments. “By 6 am the next morning, the dog has undergone a 12-hour fast. It happens every single day. So if you give your dog an extra meal at, say, 11 o’clock the night before an operation and the surgery doesn’t occur until 2 the next afternoon, it’s only a few more hours tacked on to the usual fasting period. It’s not such a big deal.
“I had surgery last February,” Dr. Karas says. “I had to show up at 7 AM, but then the operation had to wait because of a backup in the OR. No one said, ‘Why don’t you just have a little snack?’ I survived the extra wait time just fine.
“Animals in the wild, as well as people, can go several days without eating,” Dr. Karas points out. In fact, while a person can go only a few days without water (which is never restricted before a surgery), she can go for weeks without food. So a few extra hours for a dog is not very onerous, especially when you consider that the dog is probably nervous about being at the clinic and therefore not feeling very hungry, anyway.”
In the future, as research results catch up with actual clinical practice, people may get different pre-surgery advice for their dogs. But for now, in light of the fact that a dog is not really made to suffer by having to wait for the surgery while fasting, following the clinic’s directions is a better-safe-than-sorry route. That’s true whether the directions are to fast a pet for 6 hou
If a dog has to take certain medication every day and the medication is always wrapped in cheese or peanut butter or an edible pill pocket, it’s okay to give her the medicine in the usual way before an operation. “I think that’s fine,” Dr. Karas says. “It’s more dangerous not to have the medication than to have a tiny bit of food in her stomach that will quickly clear.”
