General anaesthesia is defined as a state of controlled unconsciousness using a combination of drugs. It is routinely required in veterinary practice for many things, not only for surgery but also dental procedures and imaging. 

Like any veterinary procedure, general anaesthesia comes with its list of complications. Even though the overall risk is low, having your cat undergo an anaesthetic can be very scary for an owner. This article will look into the risk factors for cats under anaesthesia, and how we can make it as safe for them as possible.

Let’s look at the data…

The largest study in the UK looking into risk of anaesthetic-related death is the ‘Confidential Enquiry into Perioperative Small Animal Fatalities’ (CEPSAF). Over 79,000 cats over a 2-year period were studied. The results estimate the risk of anaesthetic-related death to be approximately 0.24% in healthy cats, increasing to 1.3% in sick cats. The post-operative recovery period was the time most associated with complications, with 61% of fatalities happening during this time. 

What happens during an anaesthetic? 

The process of a general anaesthetic in cats starts with a ‘pre-medication’; which is a combination of drugs given to make the animal calmer and sleepy. This can be given into the muscle, or via an intravenous catheter. Once these first drugs have taken effect, the vet will induce anaesthesia with another anaesthetic drug which will place them into a state of unconsciousness. 

At this point, access to the airway will usually be gained by placing an endotracheal tube (a long plastic tube which fits snugly into an animal’s windpipe). This allows an inhalational anaesthetic drug and oxygen to be delivered. It also allows us to help the patient breathe if they need it. The patient will be closely monitored throughout. The veterinary surgeon is always responsible for the anaesthetic. And they will usually be assisted by a registered veterinary nurse, with the help of advanced monitoring equipment, checking oxygen and carbon dioxide levels, blood pressure and an ECG. At the end of anaesthesia, they will gradually gain consciousness again as the anaesthetic drugs wear off. And in some cases the drugs can be antagonised (reversed) to help the animal recover more quickly.

Which cats are more at risk? 

The CEPSAF regards the following as risk factors for death under anaesthetic: 

  • Poor health status and underlying medical conditions 
  • Extremes of weight (over or underweight) 
  • Increasing age
  • Increasing procedural complexity and length 

How can we make an anaesthetic as safe as possible? 

Planning ahead and pre-empting any complications that may arise is key:

Clinical examination

Your pet will undergo a thorough physical examination while they are still awake. Things to check include:

  • Mucous membrane colour – this should be nice and pink and gums should be moist 
  • Capillary refill time – this gives us more information of how good an animal’s circulation is 
  • Heart auscultation – checking the rate and rhythm is normal, and that no heart murmurs can be heard 
  • Respiratory rate 
  • Pulse quality 

Pre-anaesthetic blood tests

A blood test will give us information on red and white blood cell levels, liver and kidney function, blood glucose and electrolyte levels. Your vet will be more likely to recommend this if your pet is older (due to possible organ dysfunction). Or if your animal already has a known medical condition

Intravenous fluid therapy 

Some animals will struggle to moderate their blood pressure while under anaesthetic, and fluids can be very useful in supporting this. Maintaining blood pressure is very important to ensure good organ function.


Your cat will be carefully monitored on induction of, during, and after anaesthesia, by a highly trained individual, be that a vet or a nurse, with the help of dedicated monitoring equipment. They will be regularly checking lots of different parameters to ensure that the level of anaesthesia is appropriate, and if any interventions are required. 

In conclusion 

On the whole, it is relatively safe for a cat to undergo an anaesthetic. However, the risk will increase if they are already ill, if they’re extremely over or underweight, if they’re old, or if they’re undergoing a long and complex procedure. In these cases, anaesthesia will be performed on a risk-benefit basis. Speak to your vet if you have any concerns.