METHODS	Sixty patients aged 18-65 , weighing 45-80 kg , undergoing colectomy or pedical screw intermix were randomized into 3 groups : Groups S3 , S4 , and S5 to receive sufentanil at the fixed target plasma concentrations of 0.3 , 0.4 , and 0.5 ng/ml respectively in combination of nitrogen monoxide inhalation at 0.9 MAC .\