How Risky Is Anaesthesia for My Dog?
About 1 in 1,000 dogs in UK practice died from anaesthetic causes within 48 hours. What raises the risk, when deaths happen, and what to ask your vet.
Written by thecanineledger
This page carries no advertising, and nothing on it is for sale.
In the early 2000s, a UK study of more than 98,000 dogs found that about 1 in 600 died from anaesthetic or sedation-related causes within 48 hours (Brodbelt et al., Vet Anaesth Analg 2008). A decade later, a study of 157,318 dogs in UK practices put the figure at about 1 in 1,000 (Shoop-Worrall et al., Vet Anaesth Analg 2022).
While any anaesthetic carries some risk, for most dogs that risk is low, and it is lowest for healthy dogs having planned surgery. The risk that matters is your own dog’s. This page explains what raises it, when problems tend to happen, and what to ask.
1. The best numbers we have
The largest study of dogs in ordinary practice used records from VetCompass, a UK research programme that collects data from over 300 practices. Of 157,318 dogs given a general anaesthetic or sedation between 2010 and 2013, “there were 159 (0.10%) within 48 hours and 219 (0.14%) GA/sedative-related deaths within 2 weeks.”
For routine neutering, the risk was much lower: “Within 89,852 dogs that underwent a neuter surgery, there were eight GA/sedative related (0.009%).” That is about 1 in 11,000.
The authors’ conclusion: “The overall risk for GA/sedative related death was relatively low, particularly among the subset of dogs undergoing castration or ovariohysterectomy surgery.”
2. What raises the risk
The 2022 study found three things that raised the odds of death: “Greater age, poorer American Society of Anaesthesiologists health status scores and more urgent procedures”.
The ASA score is a grade the vet gives your dog’s health before the anaesthetic, from a healthy animal to one that is critically ill. The older UK study shows how much it matters. In healthy dogs, the risk of death was 0.05%, or “1 in 1849”. In sick dogs, it was 1.33%, or “1 in 75”.
A worldwide study of 55,022 dogs found the same pattern and added one more: “Age, obesity and a higher ASA classification score were associated with increased mortality” (Redondo et al., Vet Rec 2024).
Our note: Our description of the ASA score is from general knowledge, not a source we quote. You can ask your vet what grade your dog has.
3. Old dogs
Age raises the odds, but none of these studies gives an age at which a dog becomes too old for an anaesthetic. Age often travels with disease, and the ASA score captures how sick a dog is. An older dog with well-managed health may be a lower risk than a younger dog having emergency surgery.
Our note: That last sentence is our reasoning from the risk factors above, not a finding we’ve quoted.
4. Breeds
In the 2022 UK study, “Rottweilers and West Highland White Terriers had greater odds and Cocker Spaniels had lower odds” of anaesthetic-related death, compared with mixed breeds.
Owners of flat-faced breeds, such as Bulldogs and Pugs, are often warned about anaesthesia. A 2025 analysis of the worldwide study found that “Brachycephalic dogs showed higher crude mortality than non-brachycephalics (0.82% vs. 0.65%)”, but the difference shrank once the dogs’ health scores were taken into account (Redondo et al., Animals 2025). The authors concluded that “between-breed differences largely reflected case severity”.
Breeds with the MDR1 gene variant, such as Collies, are known to react to some drugs. In the same analysis, “MDR1-associated breeds did not differ” in anaesthetic deaths.
Flat-faced dogs still need extra care around breathing during recovery. Breed is one thing to tell your vet about, not a reason to refuse surgery.
Our note: Two lines here are general knowledge, not from these studies: that MDR1 breeds react to some drugs, and that flat-faced dogs need extra care around breathing during recovery.
5. When deaths happen
Many owners worry about the moment their dog goes under. In fact, many deaths happen afterwards. In the worldwide study, “Most deaths occurred postoperatively (81%).” In the older UK study, postoperative deaths “accounted for 47% of deaths in dogs”, and its authors concluded that “Greater patient care in the postoperative period could reduce fatalities.”
That makes recovery a fair thing to ask about.
6. Why the numbers vary
The worldwide study found a higher death rate: “Anaesthetic-related mortality was 0.69%.” That’s about seven times the UK practice figure. The two studies drew on different clinics in different countries, so they aren’t directly comparable. The worldwide study’s authors list limitations including a “non-randomised sample” and “potential selection bias”.
So the UK figure of about 1 in 1,000 is the better guide for a dog in ordinary practice. The figure for your dog depends on its health and the procedure.
Our note: We haven’t read the full worldwide paper, so we don’t know how many of its 405 centres were referral or university hospitals.
7. What to ask your vet
- What is my dog’s health grade for this anaesthetic, and why?
- Is this procedure urgent, or can we plan it? Planned procedures carried lower risk.
- Who will monitor my dog, and what will they measure?
- How will my dog be watched during recovery, and for how long?
- Would losing weight first make a difference?
- Are blood tests recommended first, and what would change if they found something?
→ Anaesthesia-Free Dental Cleaning: What the Specialists Say
8. What we could not verify
| Commonly said | What we found |
|---|---|
| “My dog is too old for an anaesthetic” | No age cut-off in the studies. Age raises the odds; health and urgency matter as much. |
| “Flat-faced dogs are much more likely to die” | Mostly explained by health. The difference shrank after adjusting for health scores. |
| “Most deaths happen during surgery” | Not in these studies. Many happened in recovery. |
| “Pre-anaesthetic blood tests make it safe” | Not studied here. We haven’t yet read the evidence on blood tests. |
Sources
- Shoop-Worrall SJ, O’Neill DG, Viscasillas J, Brodbelt DC. Mortality related to general anaesthesia and sedation in dogs under UK primary veterinary care (Vet Anaesth Analg 2022; abstract read)
- Brodbelt DC, Blissitt KJ, Hammond RA, et al. The risk of death: the confidential enquiry into perioperative small animal fatalities (Vet Anaesth Analg 2008; abstract read; data from 2002–2004)
- Redondo JI, Otero PE, Martínez-Taboada F, et al. Anaesthetic mortality in dogs: A worldwide analysis and risk assessment (Vet Rec 2024; abstract read)
- Redondo JI, Martínez-Taboada F, Hernández-Magaña EZ, et al. Breed-Specific Anaesthetic Mortality in Dogs: Evidence from an Analysis of 55,019 Cases (Animals 2025; abstract read)
Always confirm with your vet before acting on anything on this page.