Anaesthesia for an Older or Heart-Patient Dog: The Real Risk and What to Ask

The vet looks in your dog’s mouth and says the teeth need a proper clean, maybe an extraction or two. The dog is eleven, or has a heart murmur, or both. And the word that sticks is anaesthetic. Many owners put it off for a year on the strength of that word alone. This guide is about what the risk actually is, what makes it bigger or smaller, and the questions that make it smaller still.

The risk, in real numbers

The largest study we have is the UK’s Confidential Enquiry into Perioperative Small Animal Fatalities (Brodbelt and colleagues, 2008), which followed 98,036 dogs anaesthetised or sedated at 117 practices. Within 48 hours, about 1 dog in 600 died of causes related to the anaesthetic or sedation. That overall figure hides the part that matters:

Dogs in the study	Anaesthetic-related deaths
All dogs	about 1 in 600
Healthy, or with mild, controlled disease	about 1 in 1,850
With serious or uncontrolled disease	about 1 in 75

The same research found the odds rose with a sicker dog, an emergency rather than a planned procedure, a longer procedure, older age and lower body weight. The jump between the healthy and the sick rows is about twenty-five times. That is the number to hold on to: the biggest single thing you and your vet can change is how well the dog is going in. The data was collected between 2002 and 2004, and monitoring has improved since, so treat these as cautious figures rather than today’s exact odds.

One more finding changes what you should ask about. Nearly half of the deaths in dogs (47%) happened after the procedure had finished, in recovery, and many of those in the first few hours. The time after the anaesthetic matters as much as the time during it.

Age is not a disease

Vets have a saying for this, and it is a fair one. A twelve-year-old dog with normal blood results, a stable heart and a planned procedure is in the healthy row of that table. A six-year-old with untreated kidney disease is not. Older age does add some risk, but it does not decide on its own; what the tests find does.

Waiting also has a cost. Gum disease and infected teeth are painful, and a small dog will usually keep eating through the pain, so it is easy to miss. The longer a mouth is left, the more teeth tend to need removing, which means a longer anaesthetic, in an older dog, later. Cleaning without an anaesthetic is not a gentler version of the same thing: the American Animal Hospital Association’s dental guidelines call it inappropriate, because the part that matters, under the gum line, cannot be cleaned or examined in an awake dog. Our guide to bad breath and teeth explains why.

Before the day: the checks worth asking for

Not every dog needs every test, and your vet will decide what fits. These are the checks commonly done for an older dog, and what each one is looking for:

Check	What it looks for	Most useful when
Full examination, listening to heart and lungs	Murmurs, irregular rhythm, breathing problems	Always
Blood tests	Kidney and liver function, anaemia, blood sugar	Older dogs, or any dog on long-term medication
Urine test	Kidney function and infection, alongside the bloods	Drinking more, or borderline kidney results
Heart ultrasound (echocardiogram)	Whether a murmur has enlarged the heart, and how much	A murmur, especially a new or louder one
Chest X-rays	Heart size, fluid in the lungs	Coughing, fast breathing, or a known heart problem
Blood pressure	High pressure, common with kidney disease	Older dogs, kidney or heart disease

If something turns up, it is not necessarily a no. Often it means treating that first, choosing different drugs, or giving fluids during the procedure. That is the tests doing their job.

If your dog has a heart murmur

In an older small dog, a murmur most often comes from a leaking mitral valve, the commonest heart disease in small breeds. In UK vet records of Shih Tzus, murmurs were recorded mainly in older dogs, at a median age of 11.4 (our guide to that study has the detail). Many dogs live with one for years.

For an anaesthetic, the murmur itself matters less than what it has done to the heart. Cardiologists stage valve disease (the ACVIM consensus of 2019): a murmur with a normal-sized heart, a murmur with an enlarged heart, and heart failure. That staging needs a scan or X-rays; listening alone cannot tell them apart. A dog with a murmur and a normal-sized heart is often a reasonable candidate for a planned procedure. A dog in heart failure is usually stabilised on treatment first, and anything that can wait, waits.

Two things help from home. In the week before, count the breathing rate while the dog is fast asleep, as our guide to the older small dog describes, and tell the vet if it is climbing. And ask exactly what to do about heart medication on the morning: whether to give it, and with how much food.

Short-nosed breeds need extra care in recovery

Shih Tzus, Pekingese, Pugs and other flat-faced breeds can have narrow nostrils, a long soft palate and a small windpipe. Under anaesthetic the breathing tube protects the airway; the risky moment is after it comes out, while the dog is still drowsy. One study of procedures other than airway surgery found problems after the operation in about 14% of short-nosed dogs, against under 4% of other dogs. This is why many vets leave the tube in until a flat-faced dog is properly awake, and watch it closely for some hours after. It is a fair thing to ask about.

What to ask your vet

1. Which tests do you want first, and what would change your plan?
2. If there is a murmur: do you want a scan before, and does the result change the drugs you use?
3. Who watches my dog during the anaesthetic, and what is monitored? (Heart rate and rhythm, oxygen, breathing, blood pressure and temperature are the usual list.)
4. Will there be a drip (intravenous fluids), and how do you keep a small dog warm?
5. For a dental: will you take dental X-rays, so anything that needs doing is done under this one anaesthetic?
6. Who watches my dog in recovery, and for how long before I can collect?
7. What pain relief will it go home with?
8. What should I do about food and medication the night before and on the morning?

A good practice will be glad you asked. Follow their fasting and medication instructions exactly, even if they differ from what you did for a previous dog: advice on fasting has changed over the years, and it depends on the dog.

The first day home

Expect a sleepy, slightly wobbly dog for the rest of the day. Keep it warm and quiet, somewhere low it can step into rather than jump onto, like a firm foam bed on the floor, and away from stairs. Offer a small meal in the evening if the vet says so; after extractions, soft food for as long as they advise. Give the pain relief as prescribed, not only when the dog looks sore.

Call the vet, that day, if you see:

• Breathing that is fast, laboured or noisy at rest, or gums that look pale, grey or blue.
• Collapse, or a dog you cannot rouse.
• Repeated vomiting.
• Bleeding from the mouth that does not stop.
• Not eating at all by the next day.

Making it the last dental for a while

A clean under anaesthetic resets the mouth; it does not keep it clean. Once the vet says the gums have healed, daily brushing is what stretches the time to the next one. Start with a few seconds a day, on the outside surfaces of the back teeth, where tartar builds first. A soft finger brush can be easier to begin with on a dog that is not used to it. Brushing will not remove tartar that has already hardened; it only stops new tartar building up.

None of this makes an anaesthetic risk-free, and no honest vet will say it is. But for a well-prepared older dog having a planned procedure, the risk is small, and the pain of a bad mouth is not. The decision belongs to you and your vet, and it is a much easier one with the tests in front of you.