After approximately @ minutes , a dexmedetomidine infusion was started ( @ g kg ( -@ ) then @ g ( -@ ) kg ( -@ ) hour ( -@ ) ) in combination with either saline ( group S ) , morphine ( @ mg kg ( -@ ) then @ mg kg ( -@ ) hour ( -@ ) ; group M ) , or remifentanil ( @ g kg ( -@ ) hour ( -@ ) ; group R ) for @ minutes .