One of my clients today had a friend who lost their dog recently. The friend's dog was spayed on Friday, and died Saturday, apparently from excessive bleeding. My client has a 14 week old boxer puppy, and was very concerned about her safety when she was spayed. That's a valid concern, and one worth talking about.
Routine surgeries such as spays and neuters are considered very safe. Now realize that not all veterinarians do them the same way. I always recommend pre-anesthetic blood testing, an IV catheter, monitoring with an ECG and pulse oximeter (measuring blood oxygen), sevoflurane anesthetic, and perioperative antibiotics and pain medication. Not all vets will use these. Believe me, I've seen it, and at one point even did it. If blood tests are not performed, you might miss hidden health problems, even in young dogs. I've discovered many subclinical problems this way. An IV catheter and fluids not only helps to maintain blood pressure, but if the patient begins to have problems, you already have a direct line to the cardiovascular system, and don't have to waste precious minutes placing a catheter in a critical patient. Proper monitoring of the heart allows you to catch problems during the procedure that could lead to cardiac arrest. Sevoflurane is currently the safest veterinary gas anesthesia in the US, and patients recover very quickly for it. There are many valid reasons for vets making these recommendations, and making money really has nothing to do with it.
The puppy that died did have all of these precautions. Yet something bad still happened. Unfortunately, nobody can say that surgery carries no risk. This is true of human medicine as well. People do die of routine procedures, and this is a risk you acknowledge when you sign the authorization forms at the hospital (read the fine print sometime...one of the lines usually states something about you understanding that the procedure carries a risk of death). The nature of medicine, surgery, and physiology is that we can't predict or control 100% of possible factors. There will be circumstances where a patient will have complications or even die despite every precaution being taken. That's very scary to consider, and something nobody wants to contemplate.
Thankfully, complications are very rare. The best veterinary facilities normally run a complication rate of 1 case per 10,000 procedures, which mirrors the rate among human surgeries. I have calcuated my own cases, and I have easily done over 3,000 routine spays and neuters in my career so far. I have lost only one patient to a routine procedure, and that was traced to a failure in the anesthetic machine. Keep in mind that I'm talking about risks in routine procedures. I have other patients during or shortly after surgery, but those were serious cases that carried many more risks. A major surgery such as removing a spleen, relieving an intestinal impaction, or repairing a ruptured diaphragm carries much more potential for complications. The risks for a spay, neuter, or dental cleaning are considered minimal.
If you have concerns about your pet being anesthetized, ask your vet to detail the procedure. Good vets will be happy to describe in detail how they do it and will try to allay your fears. We do spays, neuters, and dentals multiple times each day and rarely think twice about it. Any risks are minimal, even in very old dogs and cats (assuming the pet is generally healthy), and are far outweighed by the benefits of the surgery.
And the client whose friend lost her dog after spaying? She's still going to have her boxer puppy spayed.