OBJECTIVE:To explore the effects and safety of dexmedetomidine combined with remifentanil on postoperative cognition and hemodynamics in patients underwent colon cancer surgery.METHODS:One hundred undergoing colon cancer sur gery in our hospital during Jun.2013-Apr.2016 were selected and divided into control group and observation group according to random number table,with 50 cases in each group.Control group was given Remifentanil hydrochloride for injection 2-4 μg/kg for anesthesia induction,with maintenance dose of 0.5-2 μg· kg/min;observation group was treated with Dexmedetomidine hydrochloride for injection 0.5 μg/kg and remifentanil 2-4 μg/kg for anesthesia induction,with maintenance dose of Dexmedetomidine hydrochloride for injection 0.4 μg·kg/h+Remifentanil hydrochloride for injection 0.5-2 μg·kg/min.MMSE score and the incidence of postoperative cognitive dysfunction (POCD) were observed in 2 groups 1,2,3 d after surgery,and the occurrence of ADR was record ed.RESULTS:The incidence of POCD in observation group 1,2,3 d after surgery were 16.0％,4.0％,6.0％,which was signifi cantly higher than 36.0％,12.0％,10.0％ of control group,with statistical significance (P＜0.05).There was no statistical significance in MMSE score between 2 groups 1,3 d after operation (P＞0.05).2 d after surgery,MMSE score of observation group was significantly higher than that of control group,with statistical significance (P＜0.05).There was no statistical significance in hemodynamic indexes,the incidence of ADR as blood pressure increasing,amyostasia,nausea and vomiting between 2 groups 1,2,3 d after surgery (P＞0.05).CONCLUSIONS:Dexmedetomidine combined with remifentanil can significantly improve postoperative POCD in patients underwent colon cancer surgery and have little effect on hemodynamics with good safety.