Abstract:Objective To investigate the influence of ropivacaine combined with different doses of esketamine for serratus anterior plane block （SAPB）on postoperative negative emotions and analgesic effect in perimenopausal patients undergoing breast surgery.Methods Ninety-six patients scheduled for breast surgery at the Affiliated Hospital of Jiangnan University between September and November 2025 were enrolled. Patients were aged 45-55 years，with an ASA physical status of Ⅰ-Ⅱand a BMI of 18-30 kg/m². Under ultrasound guidance，SAPB was performed after general anesthesia induction. Patients were randomly divided into three groups（n=32 each）：Group R（ropivacaine alone，0.375% ropivacaine 20 mL），Group ESK1（0.25 mg/kg esketamine combined with 0.375% ropivacaine 20 mL），and Group ESK2（0.50 mg/kg esketamine combined with 0.375% ropivacaine 20 mL）. Positive Affect and Negative Affect Schedule（PANAS）scores were recorded one day preoperatively and on postoperative day（POD）1 and POD3. Visual Analog Scale（VAS）scores on motion were recorded at 2 h，8 h，24 h，and 48 h postoperatively. The incidence of adverse reactions（nause and vomiting，delirium，respiratory depression）were monitored. Results All 96 patients achieved effective nerve block. There were no statistically significant differences in surgical type，age，BMI，or ASA classification among the three groups（P>0.05）. Generalized estimating equation（GEE）analysis revealed significant inter-time effect，inter-group effect，and interaction effect for positive and negative emotion scores across the three groups（P<0.01）. The improvement rates of negative emotions on POD1 were 68.75%，43.75%，and 25.00% in the Group ESK2，Group ESK1，and Group R，respectively；the corresponding rates on POD3 were 81.25%，59.38%，and 34.38%，respectively. The Group ESK2 exhibited the highest improvement rate at both time points，with statistically significant differences among the three groups （χ²=12.420，P<0.01；χ²=14.486，P<0.01）. The Group ESK2 had significantly lower VAS scores on motion at 2 h，8 h，and 24 h postoperatively compared with the Group R and Group ESK1（P<0.05）. No statistically significant difference was observed in the incidence of adverse reactions among the three groups（P>0.05）. Conclusion The combination of 0.5 mg/kg esketamine and ropivacaine for SAPB provides superior analgesia，does not increase adverse reactions，and significantly improves negative emotions. This regimen represents an optimal dose for synergistic postoperative pain and depression management in perimenopausal patients undergoing breast surgery.