Preoperative is about the time before a medical operation: tests, forms, 'do not eat after midnight', the nervous wait. Nurses often shorten it in speech to pre-op. After the operation is postoperative; during it there is a rarer word, intraoperative. This is hospital English. It can sit in front of many nouns: preoperative assessment, preoperative anxiety, preoperative fasting. It is not the same as operational, which means a machine or a plan is up and running, and it is not a general word for 'getting ready'. Only the hours and days before surgery.