Erin, yeah going without the oxy could have caused the nausea, if he has been on it for awhile. I don't mean to butt in, but with stage 4 cancer, I would think his doc would have him on different pain meds, like a long acting and something for breakthrough. It's terrible that he had to wait and go without his meds. I'm so sorry you guys had to go through that. If he was on a long acting pain med, he would keep a more even level of meds in his system and then when the pain breaks through that, he would take a short acting pain med. It might give him much better control of his pain. Of course I am assuming here so if his pain is controlled, forget I said anything.
Also while I've already given unsolicited advice does his doc prescribe him something for nausea? That way you might not have to have runs to the ER.
By the way, I have had cancer (stage 3) as well, so I know how hard it is.