Group I : remifentanil 0.25 microg kg ( -1 ) ; Group II : remifentanil 0.50 microg kg ( -1 ) ; Group III : alfentanil 15 microg kg ( -1 ) ; Group IV : alfentanil 20 microg kg ( -1 ) 60 s prior to propofol mixed with 1 mL of 0.9 % normal saline ; Group V : lidocaine 1 mL of 1 % ( 10 mg ) added to 100 mg of propofol and Group VI : normal saline .
