Anything that happens before a patient has surgery is preoperative. Your preoperative instructions might include not eating or drinking anything for several hours.
People who have their wisdom teeth or their tonsils removed are given a preoperative checklist to help them prepare for the operation. These patients usually have preoperative medication that makes them sleepy or unconscious during the procedure. Doctors and nurses follow preoperative instructions of their own, including hand washing and preparing the site of the surgery.