Does euthanasia without sedation hurt?

My dog was 13 and experiencing mobility issues and showing signs of discomfort. She also had early breast cancer. When we had her euthanized, we opted to not use sedation and instead gave her treats to distract her while the vet administered the medicine. She didn’t outwardly show signs of pain or anxiety; she was happily eating spray cheese one second, then seemingly frozen the next. The vet waited to for heart to stop, but it took longer than expected. Was she in pain? Was she not ready to go? Why did her heart keep beating for so long, and should we have used sedation?

Hello and thank you for this excellent question.  Euthanasia can be difficilt to watch, especially given how sheltered from death we - as human beings - are in the modern world, often only experiencing the process close-up for the first time when it happens to an animal or person we love.  I massively appreciate your raising the subject,  because it should be talked about more.  So without further ado....

I don't think that anyone can know for sure what an animal experiences when euthanasia happens to them, but I do know that the body is a multi-cellular, multiple organ structure and that different areas of it will 'shut off' at different times; that there is not necessarily one exact moment of death (for example we know that parts of a limb can die off from frost-bite and the heart and brain still be fine).  Similarly, I like to think from this description that your pet lost consciousness very quickly, even though the heart continued to beat for a while; it sounds as though they were with someone likely loved - eating with a human 'pack member' right to the end - and were glazed and completely unconscious when their heart stopped.  I'm so sorry to hear about your loss - there is never a 'right time' to say goodbye to someone you love - and I hope that this helps a little.

Regarding pain, injections can be uncomfortable but they don't sound to have been fazed by it; your vets distraction technique sounds to have been a reasonable one in this case.  Most vets I know do tend to sedate; that way, if a needle slips or a second injection is required, the patient may remain unaware of it.  For some, it also removes any doubt of awareness.   In this case however, it sounds as though I would have been satisfied that euthanasia was very humane.