The effect of low‐dose ketamine on postoperative quality of recovery in patients undergoing breast cancer surgery: A randomised, placebo‐controlled trial

BACKGROUND Low-dose ketamine has been proved to reduce opioid consumption, prevent depressant action and improve postoperative analgesia. Women undergoing mastectomy experience may not only have persistent postoperative pain syndromes but also emotional problems. However, the effect of intraoperative infusion of low-dose ketamine on postoperative quality of recovery among these patients has not yet been fully studied. METHODS In this prospective, randomised, single-centre trial, 100 patients planned for modified radical mastectomy were randomly assigned to one of two groups: control group (group C) or ketamine group (group K) at a ratio of 1:1. Group K received the bolus dose of 0.5 mg/kg ketamine and followed by 0.25 mg·kg-1 ·h-1 after the compliment of anaesthesia induction until the end of the surgery, whilst group C received an equivalent dose and regiment of normal saline was group K. The primary outcome was to assess the effects of low-dose ketamine on postoperative quality of recovery using the 40-Item Quality of Recovery (QoR-40) scale on a postoperative day 1 (POD1). The secondary outcome was to assess the numeric rating scale (NRS) at 4, 24 and 48 h after the operation, identity-consequence fatigue scale (ICFS) scores at 3 and 7 days after the operation, hospital anxiety and depression scale (HADS) scores at 2 days and 3 months, as well as chronic pain at 3 months. In a post hoc analysis, the 5 subsections of the QoR-40 scores were also analysed. RESULTS A total of 100 subjects were randomised. The primary outcome of QoR-40 scores on POD1 was available in 97 patients (49 in group C and 48 in group K). Global QoR-40 scores were not significantly different between group C and group K (169.8 ± 10.7 vs. 172.7 ± 7.5, 95% CI -1.35 (-5.50, 2.80), p = .519). In a post hoc analysis, pain scores were significantly higher in group K than in group C (29.8 ± 3.8 vs. 31.7 ± 2.1, 95% CI -1.81 (-3.00, -0.62), p = .003). The secondary outcomes, including NRS, ICFS scores, HADS scores and chronic pain had no difference between groups (p value for each >.15). CONCLUSION Intraoperative low-dose ketamine infusion did not improve the overall quality of recovery on POD 1 in patients undergoing breast cancer surgery.