To observe the safety and efficacy of patient-controlled intravenous analgesia （PCIA） with low-dose esketamine combined with sufentanil after off-pump coronary artery bypass grafting （OPCABG）.

Sixty patients undergoing OPCABG under general anesthesia were randomly divided into group S and group ES, with 30 patients in each group. The anesthesia induction and maintenance programs of the two groups were the same. Immediately after the operation, the group ES was injected with esketamine 0.05 mg·kg^-1 intravenously, followed by continuous infusion of esketamine 0.5 µg·kg^-1·min^-1 for 72 h with equal volume sodium chloride injection in the group S. Then PCIA（ sufentanil 1.8 µg·kg^-1 in the group ES, sufentanil 3 µg·kg^-1 in the group S） was performed immediately for 72 h. The opioid dosage,analgesia satisfaction, effective pressing times of analgesia pump, rescue analgesia rate, pain and sedation score and vital signs in the two groups within 72 h after operation were observed. The time of awakening, extubation and exhaust after operation was recorded, the level of serum troponin was detected on the 4th day after operation, and the adverse drug reactions were observed within 72 h after operation.

Compared with the group S, the dosage of sufentanil and morphine decreased, the satisfaction of analgesia was higher, the rate of rescue analgesia was lower, and the Prince-Henry pain score at 12, 24, 48 and 72 h after operation in the group ES was significantly lower than that in the group S（ P<0.05）.There was no significant difference in awakening time and Ramsay sedation score, heart rate, mean arterial pressure and central venous pressure between the two groups at 6, 12, 24, 48 and 72 h after operation. There was no significant difference in the level of serum troponin between the two groups on the 4th day after operation（ P>0.05）. Within 72 h after operation,the incidence of nausea, vomiting and hypoxemia in the group ES was significantly lower than that in the group S（ P<0.05）,and there was no significant difference in the incidence of hypertension and skin pruritus（ P>0.05）.

Low-dose esketamine combined with sufentanil PCIA can be safely used after OPCABG, and can significantly reduce the dosage of sufentanil and improve the analgesia satisfaction of patients.