Nitrous Oxide side effects?

I have a series of dental work I have to get done coming up with the first appointment earlier today. I have always had anxiety at the dentist so we decided to try Nitrous Oxide to help with that. However, maybe a minute after turning on the nitrous, I started to feel really warm in my face and neck, so warm that they actually had to shut the nitrous off. Does anyone know is this is a common side effect? I take a pretty strong narcotic medicine on a daily basis if that makes a difference.