Objective To investigate the effects of esketamine on respiration,complications and acute phase inflammatory factors in patients undergoing single-port thoracoscopic surgery under general anesthesia with preserved spontaneous respiration.Methods Ninety patients,aged 16～74 years,BMI 18～28 kg/m2,ASA physical status Ⅰ or Ⅱ,who were scheduled to undergo single-port thoracoscopic surgery under general anesthesia were selected.Patients were randomly divided into two groups by random number table:esketamine group(group E,n=45)and control group(group C,n=45).Esketamine 0.5 mg/kg was given for induction of anesthesia,and 0.25 mg/kg again before cutting skin.In group C,sufentanilwas given at 0.15 μg/kg for induction of anesthesia.Other anesthesia induction and maintenance durgs in both groups were the same.SP02,PaCO2 and PaO2 were recorded at the patient's entrance(T0),before pleuraopening(T1),15 min after pleuraopening(T2),30 min after pleuraopening(T3),and beforelaryngeal mask removal(T4).3 mL of blood was extracted from themedian cubital vein at T0 and 24 h after surgery(T5)todetect the concentrations of TNF-α and IL-6.The length of spontaneous respiration recovery and laryngeal mask removal,the number of respiratory intervention,the incidence of body movement during operation,nausea,vomiting,psychiatric symptom,awareness,the length of hospital stay was recorded.Results Compared with group C,PaO2was significantly decreased and PaCO2was significantly increased in group E at T1,PaO2was significantly increased and PaCO2was significantly decreased at T2(P<0.01).Compared with group C,the length of spontaneous respiration recovery was significantly shortened and the number of respiratory intervention was significantly decreased in group E(P<0.01).Compared with group C,the concen-trations of TNF-α and IL-6 in venous blood in group E at T5 was significantly decreased(P<0.01).There were no significant difference in the length of laryngeal mask removal,and the incidenceofcomplications,hospitalstay between the two groups.Conclusion Esketamine reducesintraoperative respiratory depression,shortens spontaneous respiration recovery,maintains respiratory stability and reduces acute inflammatory response in patients under general anesthesia with preserved spontaneous respiration for single-port thoracoscopic surgery.