I am so sorry for your loss. It's so difficult to lose a treasured pet, they touch our hearts like nothing else.
I know it's not much help, but I will attempt to explain what happened and why the vet did what he did with your little Pug.
Sometimes something called a thrombus will form. A thrombus is a collection of platelets and fibrin that form when conditions are just right. Sometimes part of this thrombus will break off and travel and this is what is known as an embolus. The embolus will travel and when it reaches a point where the vein it is traveling through is narrower than the size of the embolus, it stops and forms a blockage. In small animals like dogs and cats this typically results in sudden death. Had the embolus presented with the doctor in attendance, he MAY have been able to inject a clot-busting drug to quickly dissolve it, however if this is not done pretty much as soon as the very first sign of distress is seen, it's too late to save the animal. Even if the vet HAD done CPR there would have been no way to bring your dog back. He probably should have explained this to you so that you knew that he had done all that he could, but sometimes during very emotional situations such as this things can get overlooked.
Once again, I am very sorry for your loss.
Ghilly
So sorry you lost your pug.
That is a hard question to answer and many factors can come into play. I am no expert but I am sure there is a time factor there. Sounds like thus started at home and you went directly to the Vet and the Vet didn't arrive until after you did so how much time elapsed? Does your sister know how to do CPR on a dog? Was an airway established and did she breath into the mouth and nostrils? Did you check for a pulse? The brain cannot go for that long, in normal circumstances, without oxygen. I assume the Vet checked for pulse? Depending on the time there was no breathing and if there is no pulse, the chances of recovery would be slim to none or there could be possible permanent brain damage.
Not defending the Vet, as I was not there, and might ask the same questions myself, however, if I were dealing with my Vet, whom I have gone to for years, I would trust his call on this type of scenario.
It sounds like your dog was compromised, as it was , from the major surgery. I lost my father after similar surgery. He was post op in ICU and every effort way beyond CPR was attempted to save him but he did not survive.
If you are still questioning this, I suggest you call your Vet and ask these questions and you may find a little more clarity. You certainly have every right to do this.
Again, sorry for your loss, very sad.