There are a huge number of possible reasons we have to give a dog an anaesthetic:
- Routine, or elective surgery (such as neutering, or a dental)
- Emergency surgery (such as in a dog who’s got an intestinal blockage); diagnostic procedures (like skin biopsies)
- Occasionally in severe seizures or poisonings.
However, we tend to focus on the procedure and not the anaesthetic itself – so how much do you know about anaesthetics in dogs?
What types of anaesthetic are there?
We generally distinguish between three different types of “anaesthetic”:
- Sedation – drugs are used to place the dog in an artificial sleep state. Many of the drugs used have reversing agents (drugs that can be used to counteract the sedative, waking the patient up – such as atipamezole for medetomidine). Some drugs result only in tranquillisation (e.g. acetyl promazine or ACP), where the dog is still awake but sleepy.
- Local anaesthetic – a drug is injected or applied to the skin that blocks nerve transmission, so that the dog cannot feel whatever is being done. Local may be used in addition to other techniques for better pain relief; for “while-you-wait” stitch-ups and similar minor procedures; and for epidurals.
- General anaesthetic – drugs are used that reversibly shut down all higher brain functions, keeping the dog unconscious for however long they last in the system.
What is the difference between sedation and general anaesthesia?
A sedated dog is asleep, but their normal protective reflexes are still intact (so they blink, protect their airways, and will withdraw from pain). If stimulated enough, a sedated dog will wake up, despite the drugs.
A dog under general anaesthesia may respond to painful stimuli, but will not wake up; they will also progressively lose their protective reflexes. An overdose of a sedative may cause problems with heart function and blood pressure, but overdose of a general anaesthetic will be fatal.
When you bring your dog in, we’ll give them a careful check over for signs of any underlying condition that may impact the anaesthetic. We’ll also offer you pre-anaesthetic blood tests, to check your dog’s liver and kidney function. Assuming there aren’t any problems that would prohibit a general anaesthetic, we’ll then give them a premed – a combination of sedative and painkiller that will give them a smoother anaesthetic and a more comfortable recovery. In addition, the use of a premed means we can use lower doses of anaesthetic, making side effects less likely. While that works, we’ll move them into a quiet kennel.
When we’re ready to begin, we’ll bring your dog down to the prep area for induction. This is normally done with an injectable drug (propofol) which we can give “to effect”, so the minimum dose is used; but can also be done with an inhalational anaesthetic given by mask. At this point, we’ll put a tube down their throat to help them breathe (an endotracheal tube), and connect it to an anaesthetic machine which will supply anaesthetic gas (usually isoflurane) to keep them asleep, and oxygen. At all times while they’re asleep, one of our nurses will stay with them, monitoring them constantly until they wake up again.
When the procedure is over, we’ll turn off the anaesthetic gas and allow your dog to breathe pure oxygen until they wake up.
How risky is it?
Across the board, the average mortality for healthy dogs is about 0.12% – so roughly one in twelve hundred. For dogs who are ill, however, the risks are about ten times higher (which is why we always prefer planned surgeries rather than leaving things until they turn into an emergency).
How can we minimise the risks?
The most important thing is to have all the information. That means telling us about any underlying conditions, doing any surgical procedures before your dog becomes systemically ill, and having pre-anaesthetic blood tests in older dogs. Remember, though, older dogs are not at higher risk because they’re older – just because it’s more likely they have an underlying medical problem.
Should I be worried if my dog needs an anaesthetic?
We wouldn’t be recommending a procedure requiring anaesthesia unless the benefits outweighed the risks. All our vets and nurses are fully trained in anaesthesia – as we’re all taught at vet school, there’s no such thing as a safe anaesthetic, only a safe anaesthetist!
If you’re at all concerned, have a chat to one of our vets!
For more information on the statistics, see here: https://www.rvc.ac.uk/Media/Default/staff/files/dbrodbelt-thesis.pdf