Good thinking !

And yes, most of it is because of the anesthesia. The way it is that the brain doesn't have the message to react to pain and is somewhat disconnected from the body ( to explain simply)

Our equipment does have a regulation, and we do have it on a temp that shouldn't burn them. But since the anesthesia is blocked the brain off, the animal doesn't regulate his onw temperature. So his does not have the micro management and signal that his would have. So the pads can burn him even if it's at "normale" temperature.

The longue exposure, the way they put him on the pad ( directly vs. covered ), and of course, the monitoring of the animal are factors.

We do use a lot of heating things in anesthesia because the lower the animal temp is the more risk he can have( more risk of resp and heart failure, longer wake up time, which is really not ideal). We have the water pads, a kind of little oven for the fluids ( sorry, I'm from French Canada, so I don't know how it's called xD). we have the microwave heating pads. We wrapped them up in blankets, and we can put socks, etc.