Laughing Gas Fainting?

I play a ton of tennis and at times have nearly fainted on the court for no clear reason. I learned that if I drink gatorade before and during matches I don't have any problems, so the issue may lie with sugar consumption. But I recently went to the dentist to have my wisdom teeth removed, and started to pass out during the laughing gas. I didn't panic because of the mask nor did I panic because of the IV I was getting at the same time. I felt far better after I was switched back to breathing normal O2. I hadn't eaten or drinking anything in maybe 17 hours, so could the nitrous oxide have reduced my oxygen intake enough to resemble a state of exercise, and an obvious lack of sugar caused me to nearly faint? Or is that the purpose of laughing gas, making you feel faint? One thing is for sure, I'm familiar with the feeling that I had, one of sickness and confusion. I can't imagine that's the purpose of the gas, as others who have had similar procedures describe a warm interesting sensation. Thanks!