[Effect of perioperative multi-day low dose ketamine infusion on prevention of postmastectomy pain syndrome]

Objective: To investigate the effects of multi-day low dose ketamine infusion for postmastectomy pain syndrome (PMPS) after breast cancer surgery. Methods: This study was a prospective randomized controlled trial. From June 2015 to May 2016 in Affiliated Yiwu Hospital of Wenzhou Medical University, 66 patients with breast cancer surgery were randomly divided into control group (group C) and ketamine group (group K). Patients in group K were infused with 0.5 mg/kg of ketamine mixed in 250 ml of 0.9% normal saline in 1 h daily for 7 days. Patients in group C were infused the same dose of 0.9% normal saline. Anesthesia induction in both groups were given intravenous midazolam, sufentanil, propofol, vecuronium and intermittent positive pressure ventilation after tracheal intubation, anesthesia was maintained with propofol and remifentanil. After awakening, all patients were monitored in postanesthesia care unit (PACU) and given patient-controlled intravenous analgesia(PCIA). Pain scores were assessed using visual analogue scales (VAS) during PACU, 4 h, 24 h and 2-5 d after surgery, simultaneously analgesic requirement were recorded. Patients were evaluated Hospital Anxiety and Depression Scale (HADS) 5 d after surgery . The patients were followed up for 6 months. At 3 m, 6 m after surgery, the incidence of PMPS, the level of pain, pain site and HADS scale were assessed. Results: The VAS score uring PACU, 4 h, 24 h and 2-5 d after surgery in group K( (2.5±0.8), (2.4±0.5), (2.4±0.5), (2.0±0.4), (1.5±0.5), (1.0±0.4), 1(1), respectively) was lower than those in group C ((2.9±1.0), (2.9±0.6), (2.6±0.5), (2.3±0.5), (1.8±0.6), (1.5±0.5), 1(0), respectively). There was statistically difference between the two groups (all P<0.05). The consumption of analgesics required at each time postoperation in group K were also lower than that of group C(all P<0.05). Followed up for 6 months, 2 lost in group C, 1 lost in group K. The incidence of PMPS in group K at 3 months and 6 months after surgery was significantly lower(25% and 22%) than that in group C(52% and 45%)(χ(2)=4.729, 3.842, all P<0.05). There were no significant difference in pain level and site between two groups of PMPS patients (all P>0.05). There were no significant difference of HADS scale preoperative and 5 d after surgery between two groups (all P>0.05); and HADS scale in group K at 3 m and 6 m after surgery was significantly lower than that in group C(all P<0.05). Conclusion: Perioperative continuous multi-day low dose ketamine infusion can effectively reduce the incidence of PMPS after breast cancer surgery.