Objective To evaluate the effects and security of single or combined sufentanil application on sedation and analgesia for mechanically ventilated patients in intensive care unit(ICU).Method A total of 160 ICU patients with mechanical ventilation were randomly allocated into four groups:sufentanil group,sufentanil plus midazolam group,sufentanil plus dexmedetomidine group and fentanyl group.Facial pain scale(FPS),Ramsay score and vital signs were employed to assess the effects of different therapies on organ functions and adverse reactions.Result After the treatment,FPS in all groups were significantly decreased and maintained around 3 points.Ramsay scores were significantly increased(P <0.001)and the score in group given sufentanil combined with midazolam or dexmedetomidine at the time points of30 min,1 h,6 h were even higher.Compared with the preoperative data,indicators of lung function(PaCO2and blood lactic acid),liver function(AST)and renal function(Cr)were decreased in all groups(P <0.05).Respiratory rate in the fentanyl group was significantly higher than the others.Total consumption ofsufentanil in group with combined sufentanil application was significantly lower.No significant differencesin adverse reactions were noticed among the groups(P >0.05).Conclusion For mechanically ventilatedpatients,sufentanil has efficient sedative and analgesic effects with less physiological interference and severe adverse reactions.Combined application is beneficial in decreasing total sufentanil consumption andinhibition to respiratory system,which is worthy of being spread.