I am so sorry about your dog!
Statistics show that approximately one out of every 1000 or so surgeries results in morbidity or death for no apparent reason, and they never do find the cause. And this is even with pre-op blood tests, X-Rays, ECG, etc, to make sure the animal can safely undergo anesthesia.
Surgery and anesthesia for any reason is a very serious undertaking and causes great stress on the body. Stress can take many forms including heart or other organ failure. Orthopedic surgery takes longer, so your dog was under anesthesia for a longer period of time, causing his body to be further stressed. You could request an autopsy at another facility if you really wanted to try to find out the cause of death, but realize that the cause may never be found.
It is especially sad that your dog was alone when he died but I doubt he suffered very much since following orthopedic surgery, extended release pain medicine, such as a Fentanyl patches are used, as well as other strong pain medications. Lastly, there may have been microscopic metastasis, not visible on X-Rays or in blood work in your dog, and if so he may have suffered a long recuperation for little benefit.
It is really sad, but time really does lesson the wound. I have been where you are a number of times.
I believe that dogs go to heaven and have souls, and hopefully we will see them again.
Anyhow, usually only emergency 24 hour veterinary hospitals monitor their patients all night.
Thanks for your comments,
I spoke to my vet today and he told me that Tyson was on the patch Fentanyl and was given a shot for pain at 1:30am and the assitant stayed with him until 2:15am. The vet found him at approx.7:00am dead. I am just so worried he suffered or was scared as he did not know what was going on. I cannot get this out of my head. I have lost 2 other dogs close to this age but this one really bothers me as I question wether I should have put him through the surgery even though the vets thought he would make it. This loss is hard to stomach and I have so many questions. I wonder why they would ever leave him unattended for that amount of time after such a serious surgery and wether they would of been able to do any-thing for him if it was his heart. I hope it was fast...I guess I am just going to have to accept the fact he is gone and is not suffering any-more. Even though I miss him so much! He was so happy when I took him in.
Thanks again, and I do believe the same as you. It was good to hear that not a vets monitor all night. I found out the maximum time he was left was 4 or 4.5 hours and was medicated so hopefully his pals where there waiting for him