I had to do this when I went in vacation and could find no one to take care if him.
I kept his lights on but dropped the temperature to 72 degrees.
His metabolism just slowed down. He did eat a little bit and pooped once.
When I came home I turned his heat back up and he was just fine. No stressing. He acted like nothing happened.
Maybe you could try this??
Now don't be too mean to me guys. I know iguanas don't naturally hibernate, but when those in Florida get cold, they do shut down a bit until it warms back up.
I've also kept his heaters are off before taking him to the vet so he is calm.