Let’s talk about anesthesia. To pet owners, it can sound like a scary thing to be avoided at all costs. To us veterinarians, though, it is a daily and necessary part of keeping your pet healthy. When we do it well and safely, we can fix common pet problems like broken teeth and really bad ear infections. Although anesthesia sounds like a scary word, just think about doing any sort of medically necessary procedure without it (remember doctors used to be called “sawbones”?). With modern protocols and medications, people and animals don’t experience pain during these procedures, but we’ve all heard about somebody’s loved one having a problem or even died when they “went under”, and so the fear remains. So, the question we’re going to answer today is, how high of a risk is it? And, how worried should you be if we recommend an anesthetic procedure for your pet?

A study from the UK reviewed every procedure using anesthesia or sedation in a large group of veterinary hospitals. They collected data from almost 100,000 procedures in dogs and almost 80,000 procedures in cats. That is quite a lot of data for a veterinary study. Then the question they asked was, “how many of these animals died and are there any risk factors?” Here’s what they found:

For all dogs, the risk of death was about 0.17%, or about one in six hundred cases. For cats, the risk was 0.24%, or about one in four hundred cases. That’s not a high risk, but those numbers are a bit misleading, and here’s why: those numbers are coming from ALL the cases the group looked at over two years. Not only were young, animals included in those numbers, but also the high risk and emergency cases such as pets that had been hit by a car or may have had cancer. The group was interested to see what the risks were for healthy and sick pets, so they looked at the numbers more closely. The numbers had to be lower for a healthy young dog getting spayed than for an old dog with a ruptured spleen tumor, right?

Yes, of course. And that is exactly what the data showed. The researchers used a scoring system to rank patients based on their overall risk for anesthesia. Here are the different classes:

 

Class 1: Minimal risk of normal healthy patient with no underlying disease. Think of a one year old dog getting neutered.

Class 2: Slight risk of a slight to mild systemic disease. Think of a cat with mild dental disease getting a cleaning.

Class 3: Moderate risk, obvious systemic disease. Think of a dog with a low grade heart murmur who needs a skin mass removed.

Class 4: High risk with severe, systemic, life-threatening disease. Think of an older cat with a blockage in its intestines that has been throwing up for three days.

Class 5: Extreme risk, moribund; patient will probably die with or without surgery. Think of a dog that has been hit by a car and is bleeding badly.

 

For simplicity’s sake, let’s call animals in Class 1 and 2 “healthy”, and animals in Class 3, 4, and 5 “sick”. When using this system, healthy dogs had their risk drop to 0.05% or one in two thousand. For healthy cats, the risk went to 0.11% or one in nine hundred. Let’s compare that with sick patients; in dogs and cats the risk of death with anesthesia is about 1.4%, which is one out of every seventy cases! Just think about that for a second. A sick dog’s anesthetic risk of death is TWENTY-SIX times higher than a healthy dogs. For cats, it’s about THIRTEEN times higher.

Well, “who cares” you might say, “my pet isn’t sick, so the risk is low”. That might be true right now, but early intervention is the BEST way to keep your pet in the low risk categories. Just think, a dog with mild dental disease that goes untreated could easily go from a Class 2 risk to a Class 3 within a year, increasing their risk of death SIX TIMES. Running that pre-anesthesia blood panel is going to help us determine which category your pet is in. This is one of the many reasons we focus on preventative medicine here at Coastal Animal Hospital.

Some of the other risk factors for anesthetic death highlight how important preventative care is. Scheduled procedures were lower risk than emergency procedures. This makes a ton of sense, and not all emergencies can be avoided, but identifying problems earlier can steer us clear of some emergency situations. Also, dogs over 12 years old had a higher risk. This doesn’t mean we can’t do anesthesia in dogs over 12, but if your pet is getting up there in age, think about scheduling some of these procedures sooner rather than later. Some of the risk factors we may not be able to change, such as herding breeds having a four times higher risk, or dogs 10 pounds and under having a seven times higher risk.

There are a lot of things that we can do to lower this risk though. On your end, preventative care to reduce risk category is one of the most important. On our end, the way we perform anesthesia obviously plays a big role. For example, if you induce anesthesia by holding a mask with an inhaled gas over a pet’s face, it is associated with a SIX fold higher risk of death than using a more balanced technique. Here at Coastal, we NEVER “mask down” our patients, and they always receive a safer combination using a premedication and the inhaled gas is for maintenance only.

Another one of the significant findings from this study was that about half of all the deaths associated with anesthesia happenedafterthe procedure was over, and most of those happened within 3 hours of finishing the procedure. At Coastal, we always ensure that our patients have a dedicated technician monitoring them, which typically only happens at large specialty or university veterinary hospitals.

So, what are the takeaways? First, we now have really good data to show that overall, the risk of death with anesthesia in dogs and cats is low, but especially low in healthy animals. Second, the risk to YOUR pet depends a lot on both keeping them healthy in the first place, AND how the anesthesia is performed. Anesthesia is not standardized amongst all veterinary hospitals, you might not get a dedicated technician, balanced protocols, or good monitoring equipment depending on where you go. At Coastal, we take great pride in offering you up to date and excellent care, which minimizes the risks for your beloved pets. For more information on how we minimize risks at Coastal – see our page on Safe Anesthesia.

 

References:

  1. Brodbelt DC, Blissitt KJ, Hammond RA, Neath PJ, Young LE, Pfeiffer DU, Wood JL. 2008. The risk of death: the confidential enquiry into perioperative small animal fatalities. Vet Anaesth Analg. Sep;35(5):365-73
  2. Matthews NS, Mohn TJ, Yang M, Spofford N, Marsh A, Faunt K, Lund EM, Lefebvre SL. 2017. Factors associated with anesthetic-related death in dogs and cats in primary care veterinary hospitals. JAVMA Mar 15;250(6):655-665