Sub-Anesthesia Dose of S-Ketamine Reduces Postoperative Pain and Anxiety in Patients Receiving Breast and Thyroid Surgery: A Randomized, Controlled Trial

BACKGROUND: Postoperative pain and anxiety affect patients’ recovery and increase the family burden. S-ketamine presents analgesic effects and anti-depressive effects in clinics. The effect of a sub-anesthesia dose of S-ketamine on postoperative pain and anxiety remains to be clarified. OBJECTIVES: This study aimed to evaluate the analgesic and anxiolytic effects of a sub-anesthesia dose of S-ketamine on postoperative pain and anxiety and explored the risk factors for postoperative pain in patients receiving breast or thyroid surgery under general anesthesia. STUDY DESIGN: A randomized, double-blind, controlled trial. SETTING: A university hospital. METHODS: One hundred twenty patients receiving breast or thyroid surgery, stratified by surgery type, were randomized to S-ketamine and control groups in a 1:1 ratio. S-ketamine (0.3 mg/kg) or an equal volume of normal saline was administrated after anesthesia induction. Visual analog scale (VAS) of pain and self-rating anxiety scale (SAS) were tested before surgery and on postoperative day 1, 2, and 3. VAS and SAS score between the 2 groups were compared, and the risk factors for postoperative moderate to severe pain were explored with logistic regression analysis. RESULTS: Intraoperative S-ketamine decreased VAS and SAS scores on postoperative day 1, 2, and 3 (P < 0.05, 2-way ANOVA for repeated measurements followed by Bonferroni post-analysis). Subgroup analysis showed S-ketamine decreased VAS and SAS scores both in breast surgery and thyroid surgery patients on postoperative day 1, 2, and 3. Logistic regression identified S-ketamine and regular exercise are protective factors, and anxiety before surgery is a risk factor for postoperative moderate to severe pain (P < 0.05). LIMITATIONS: The anxiety score in our study is not so high, which may under-evaluate the anxiolytic effect of S-ketamine. However, S-ketamine decreased the SAS scores postoperatively in our study. CONCLUSIONS: Intraoperative sub-anesthesia dose of S-ketamine reduces postoperative pain and anxiety intensity. Anxiety before surgery is a risk factor, and S-ketamine and regular exercise are protective factors for postoperative pain. The study was registered at www.chictr.org.cn with the number: ChiCTR2200060928.