My son SWCAH has had sinus problems for years and has had 21 sinus procedures under general anaesthetic, the last one being last week, (however his problem is very uncommon and is to do with the frontal sinus).  He has always been given extra IV hydrocortisone at induction and during the day of surgery.  They also check his BMI and his blood pressure carefully.  I would ask the endo for a drug protocol.  In the USA there are specialist sinus doctors, there is a very good sinus site you may like to read http://www.sinuses.com/. The doctor whose runs the site has given us some excellent advice, even though we live in the UK.  Hope all goes well.