I left my red-tailed boa outside on a cold night (40 degrees). I brought him inside, but he was very lethargic and not moving much. I put him in the bathtub with warm water and he began to move around. I then placed in back in his enclosure (which is now inside), but he continues to be lethargic and barely moves. He is breathing, but I'm worried that the cold may have caused serious damage. What can I do to help him?

Thanks,
Mike