Why shouldn't I have Advil (ibuprofen) before surgery?

Risks. Advil (ibuprofen) is an nsaid, and this class of medicine can increase your risk of bleeding, which could increase the risk of the surgery. Advil (ibuprofen) (and other nsaids) can adversely affect kidney function, which could complicate recovery from surgery. Finally recent studies appear to show increased risk of heart attack after some surgeries/procedures with nsaids.
Yes. Concerns of drug interactions. The potentiation of opioids (narcotics) used during surgery with advil (ibuprofen) (non steroidal anti-inflammatory) most likely to occur.
Blood thinner. Also it thins your blood a bit. It may cause a bit of unnecessary bleeding.