I am so sorry to hear of your loss of your pet. Its very uncommon for a pet to die during spay or neuter surgery but sometimes it happens. Usually the problem is a bad reaction to the anesthesia. If you did not do pre surgery bloodwork it might be that she had an undetected issue with the kidney's or liver or heart function that didn't allow the med to be cleared fast as it normally is. Some dogs just have a reaction to anesthesia similar to what can happen with people where their bodies just won't tolerate it.
Another issue is that sometimes dogs sneak and eat something including a stool prior to surgery and if the dog vomits this up in reaction to the anesthesia it can aspirate fluids into its lungs causing its death.
If she was a small dog sometimes they get so chilled during surgery that their body can't handle the anesthesia. With other dogs there is a sudden drop in blood sugar that leads to the pet's death.
Stress and fright can have an impact on the body's ability to handle surgery too.
You should ask your vet directly to give you a cause of death. If you were too upset to ask at the time you most certainly can call and ask that the vet call you and explain what happened.
If you have not seen this site
www.petloss.com and the rainbow bridge story it may bring you some small comfort.
Again I'm so sorry for your loss.
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