METHODS	Twelve groups of 10 patients , ASA physical status 1 or 2 , first received fentanyl 0 , 2 , or 4 micrograms.kg-1 and then 5 min later received propofol 2.0 , 2.5 , 3.0 , or 3.5 mg.kg-1 as an intravenous bolus for induction of anesthesia .\