BackgroundThe opioid sparing effect of low dose ketamine is influenced by bolus dose, infusion rate, duration of infusion, and differences in the intensity of postoperative pain. In this study, we investigated the opioid sparing effect of low dose ketamine in patients with intravenous patient-controlled analgesia (PCA) using fentanyl after lumbar spinal fusion surgery, which can cause severe postoperative pain.MethodsSixty patients scheduled for elective lumbar spinal fusion surgery were randomly assigned to receive one of three study medications (K1 group: ketamine infusion of 1 µg/kg/min following bolus 0.5 mg/kg, K2 group: ketamine infusion of 2 µg/kg/min following bolus 0.5 mg/kg, Control group: saline infusion following bolus of saline). Continuous infusion of ketamine began before skin incision intraoperatively, and continued until 48 h postoperatively. For postoperative pain control, patients were administered fentanyl using IV-PCA (bolus dose 15 µg of fentanyl, lockout interval of 5 min, no basal infusion). For 48 h postoperatively, the total amount of fentanyl consumption, postoperative pain score, adverse effects and patients' satisfaction were evaluated.ResultsThe total amount of fentanyl consumption was significantly lower in the K2 group (474 µg) compared to the control group (826 µg) and the K1 group (756 µg) during the 48 h after surgery. Pain scores at rest or with movement, the incidence of adverse events and patient satisfaction were not significantly different among the groups.ConclusionsLow-dose ketamine at 2 µg/kg/min following bolus 0.5 mg/kg significantly reduced the total amount of fentanyl consumption during the 48 h after lumbar spinal fusion surgery without increasing adverse effects.

BackgroundAquafol, a microemulsion propofol, causes more severe and frequent pain on injection than propofol. The purpose of this study was to compare a combination of lidocaine and ketamine on aquafol-induced pain with lidocaine or ketamine alone during the induction of anesthesia.MethodsIn this prospective, randomized, double-blinded study, 130 healthy patients who were undergoing elective surgery under general anesthesia were enrolled. The patients received IV lidocaine 40 mg plus ketamine 25 mg (Group LK, n = 43), lidocaine 40 mg (Group L, n = 42), or ketamine 25 mg (Group K, n = 45) with a rubber tourniquet on the forearm 1 min before the injection of microemulsion propofol. The pain score was assessed by a 4-point verbal rating scale (VRS) at 10 seconds after injection of microemulsion propofol 30 mg and during the injection of the remaining total dose.ResultsThe incidence and severity of pain was significantly lower in Group LK than Group L or Group K at 10 seconds after the injection of microemulsion propofol 30 mg (P < 0.05). And the incidence and severity of pain was significantly lower in Group LK and Group K than Group L during the injection of the remaining total dose (P < 0.05).ConclusionsPretreatment with IV lidocaine 40 mg plus ketamine 25 mg with a rubber tourniquet on the forearm 1 min before the injection of microemulsion propofol is more effective than lidocaine 40 mg or ketamine 25 mg alone in preventing pain from the injection of microemulsion propofol.

BackgroundThis study was performed to evaluate the effectiveness of intravenous low dose ketamine for reducing the incidence and severity of postoperative sore throat (POST).MethodsThis was a prospective, randomized, double-blind clinical trial. The study population consisted of 70 patients between 20 and 70 years old who were classified as American Society of Anesthesiologists I-II and were scheduled for elective laparoscopic cholecystectomy. The patients were divided randomly into two groups. Patients in the ketamine group received an intravenous injection of 0.5 mg/kg of ketamine just before induction, followed by 10 µg/kg/min throughout the operation. Patients in the control group received intravenous saline instead of ketamine. The patients were interviewed 1, 6, and 24 h after the operation. The incidence and severity of POST were recorded.ResultsNo significant differences in the incidence and severity of POST during the 24 h after the operation were found between the two groups (21/31 in the ketamine group vs. 26/34 in the control group, P = 0.398).ConclusionsIntravenous injection of low dose ketamine was not effective for reducing POST.

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