“My dog is too old for that”, is often a remark we hear as vets when we broach the topic of anaesthesia. As vets, we understand that it can be a daunting process, and some owners may be resistant to having their older pets undergo a procedure at all. This article aims to provide further insight into what we define as an ‘old’ or senior dog, what an anaesthetic might entail, and whether there actually is an age limit on dogs undergoing anaesthesia. 

When is a dog defined as ‘old’? 

We start to consider a dog as senior when, breed dependent they hit a certain age, but it definitely isn’t an exact science. According to the 2019 AAHA Canine Life Stage Guidelines, senior generally means being in the last 25% of their lifespan. For small breeds (under about 10kg), they would be classified as senior from around 10-12 years. For medium breeds (10-25kg) from around 8-10 years. For large breeds (25-45kg) from around 7-8 years. Giant breeds (over 45kg) would be classified as senior from as early as 5-6 years. 

What an anaesthetic is, and why your dog might need it 

Anaesthesia is the process of rendering an animal unconscious using a combination of drugs, both injectable and inhalational. It is usually combined with powerful pain relief. Vets require the use of anaesthesia for a wide variety of procedures, including, but not limited to: 

  • Dental procedures 
  • Surgery 
  • Imaging (x-rays, CT and MRI scans) 

Old age is not a disease! 

It sounds silly, but it’s true! While you cannot compare a 10 year old Jack Russel to a 1 year old labrador, their age alone shouldn’t be the sole factor we use as reasoning for not pursuing an anaesthetic. 

A great example of when anaesthesia is useful for an older dog is when it comes to teeth! As vets, we will frequently see dogs of 12+ with severe dental disease, which can cause long-term discomfort and potentially be a trigger for other diseases. Performing a dental cleaning, often with extractions, under anaesthetic will drastically improve that dog’s quality of life, often for years to come. Sounds pretty good right? 

What the research says 

A popular study, called the CEPSAF, is the largest, most comprehensive study of its kind, looking at outcomes of anaesthetics after 48 hours in over 98,000 dogs. Overall, 163 anaesthetic-related deaths were identified (0.17%). This includes dogs of all ages, but the study does highlight variables that affect anaesthetic safety. While it doesn’t specifically give an age at which the risk of anaesthesia increases, there is a general upward trend as the patient age increases. It is important to highlight that the study discusses ‘extremes of age’ – essentially telling us that age is one of several interconnected risk factors, and that a thorough risk assessment must be done for each patient. The main takeaway from this is that age alone as a risk factor only creates a very small increase in risk. In other words, an old dog in good health undergoing a short elective procedure is in a very different category from an old, sick dog facing emergency major surgery. 

Always consider other variables 

While age alone is not an accurate measure for risk, we know that compounding that with a worsening health status (i.e. having other health conditions) can increase the risk of death under anaesthesia tenfold. Variables that may impact on a dog’s anaesthetic risk include: 

  • Underlying disease e.g. heart disease, kidney failure, cancer 
  • Body weight, particularly being underweight. Older animals are more likely to be underweight due to generalised muscle loss, or due to an underlying health condition. Meanwhile, overweight patients have much more stress on their respiratory system – a healthy middling body condition score lowers the risk. 
  • Complexity and urgency of the procedure. An anaesthetic for an elective dental is likely to run less risk than a dog requiring emergency surgery to remove a bleeding tumour. 

In reality, an otherwise healthy 13 year old dog would carry less risk than a 6 year old dog with heart disease. 

The role of your vet 

Your vet will always weigh up the risks and benefits of a procedure before they recommend something to you. It is important to have a conversation with them to make sure you are happy to proceed with their recommendations. If the vet feels an anaesthetic is particularly risky, they will likely make this very clear. Remember that this will be a collaborative decision and should be an open discussion between owner and vet. Your vet will be able to answer any questions you have, and will likely be supportive of whatever decision you make. 

Going ahead with anaesthesia 

If you have weighed everything up and have made the decision to proceed with your dog’s procedure, there are some important further measures your vet will implement: 

Pre-operative examination 

A thorough examination is an important first step. This will involve a nose-to-tail examination of your dog. The mucous membranes (gums) will be checked for their colour, and if these are moist. The heart will be auscultated to check the heart rate, rhythm, and to listen out for a murmur. The pulses will be checked to see if these are strong and match the heart rate. A temperature will be taken. Sometimes, a pre-anaesthetic blood pressure measurement will be taken. 

Pre-anaesthetic blood test 

This is a quick, and potentially very useful tool for your vet, which can help determine if there are any underlying conditions your pet may have. It will show what their red and white cell counts are like (potentially highlighting anaemia or inflammation), and will check liver and kidney function – this is very important as these organs metabolise the drugs that we use. If there are any changes, your vet will discuss these and any associated risks with you prior to going ahead, as things like impaired kidney function may affect the anaesthetic. 

Intravenous fluid therapy (IVFT) 

Senior animals sometimes are unable to regulate their blood pressure sufficiently while under anaesthetic. Furthermore, the medications that we need to give to perform an anaesthetic can often cause the blood pressure to reduce. To help mitigate this risk, intravenous fluid therapy (specialised hydration fluid delivered directly into the bloodstream via an IV cannula) can be incredibly helpful. It also helps to support the organs, like the liver and kidneys, that excrete anaesthetic drugs. 

Generally the fluids are started before the animal has had any anaesthetic medication and will be continued throughout the entire procedure. The rate at which the fluid is given can be altered throughout, depending mostly on the dog’s blood pressure. The fluids are then continued during the dog’s recovery, often to the point where they are eating again. 

Monitoring 

Your pet will be monitored very closely by a qualified vet or vet nurse while they are under anaesthesia. These skilled professionals will use their own knowledge, but often also advanced monitoring equipment, that can check things like blood pressure, body temperature, and oxygen saturation. All of this information combined gives the nurse an outline of how the animal is doing under anaesthesia, and constant monitoring allows them to make tweaks that ensure the anaesthetic stays as steady as possible. 

In conclusion… 

It’s not as simple as putting an age cap on when a dog is ‘too old’ for anaesthesia. We must consider other things, like the animal’s current health status, the complexity of the procedure, and of course the owner’s wishes. 

As veterinary professionals, we can truly understand that anaesthesia can be a daunting process for owners. It is important to remember that it is only done when absolutely necessary, and when your vet has weighed up all the risks and benefits of their proposed treatment. 

Remember, vets and owners make decisions together, so you will always have a say in what happens to your pet. It is still worth bearing in mind that if your vet has recommended a procedure, it’s likely because they feel your pet will benefit from this, and have an improved quality of life afterwards! 

References: 

  1. Brodbelt, D.C., Pfeiffer, D.U., Young, L.E. and Wood, J.L.N. (2008). Results of the Confidential Enquiry into Perioperative Small Animal Fatalities regarding risk factors for anesthetic-related death in dogs. Journal of the American Veterinary Medical Association, 233(7), pp.1096–1104. 
  1. Creevy, K.E., Grady, J., Little, S.E., Moore, G.E., Strickler, B.G., Thompson, S. and Webb, J.A. (2019). 2019 AAHA Canine Life Stage Guidelines*. Journal of the American Animal Hospital Association, 55(6), pp.267–290.