Low-dose S+ ketamine in target-controlled intravenous anaesthesia with remifentanil and propofol for open gynaecological surgery: A randomised controlled trial

Background and Aims: Using remifentanil–propofol target-controlled infusion (TCI) in open gynaecological surgeries could be associated with opioid-induced hyperalgesia postoperatively. This study's aim was to investigate the effect of low-dose S-ketamine compared with control on cumulative morphine consumption 24 h postoperatively in women undergoing open abdominal hysterectomy with remifentanil–propofol TCI technique. Methods: Ninety female patients above 21 years old who underwent elective open abdominal hysterectomy under general anaesthesia with remifentanil–propofol TCI were recruited. They were randomised to receive either normal saline as control ( n = 44) or 0.25 mg/kg intravenous boluses of S-ketamine before skin incision and after complete removal of uterus ( n = 45). The primary outcome measure was cumulative morphine consumption measured over 24 h postoperatively. The secondary outcome measures were incidences of opioid-related and psychotomimetic side effects, pain and level of sedation scores. Results: The cumulative 24-h morphine consumption postoperatively ( P = 0.0547) did not differ between both the groups. S-ketamine group had slower emergence from general anaesthesia ( P = 0.0308) and lower pain scores ( P = 0.0359) 15 min postoperatively. Sedation level, common opioid-related side effects (nausea, vomiting, pruritus), respiratory depression and psychotomimetic side effects were similar between both the study groups. Conclusion: Low-dose S-ketamine did not reduce the total cumulative morphine consumption in patients undergoing major open gynaecological surgeries with remifentanil–propofol TCI.