Patients ( American Society of Anesthesiologists physical status I to II ) undergoing L-I were randomly assigned to receive anesthesia with propofol and remifentanil under 3 remifentanil dose conditions : 0.25 g/kg/minute ( group 1 ) , 0.5 g/kg/minute ( group 2 ) , and 0.75 g/kg/minute ( group 3 ) .