Oxygen helps and if you aren't dehydrated it is supposed to give you a "natural high."

As far as the IVs go, when I was in the military the medics would give themselves IVs after drinking heavily and swore it made a big difference, which I'm sure it did since it cures the dehydration part of the hangover.

I hate needles though so I never tried it myself. If it weren't for my fear of needles I'd probably be going to school for medical stuff instead of law school.