Comparison of two different doses of intra operative propofol infusion on post operative rescue antiemetic requiremnt after inhalational anaesthesia

Intra operatively patients will be administered with propofol infusion at the rate of 25 microgram per kg per minute in one group  and  50 microgram per kg per minute in the next group  and patients will be asessed for requirement of rescue antiemetics  for postoperative nausea and vomoting in the first four hours also as in intervals of zero  4 8 12 and 24 hours  using a 3point scale .where zero is no nausea or vomiting, one is only nausea, two is vomiting with or without nausea.