Effect of combined general anesthesia with small-dose ketamine on postoperative pain

Objective To observe the effect of combined general anesthesia with small-dose ketamine on postoperative pain.Methods Fourty patients aged 29 y-83 y(ASA Ⅰ-Ⅲ)scheduled for major abdominal surgery were randomly assigned to receive intraoperative low-dose ketamine(KG group,bolus dose of 0.5 mg/kg followed by continuous infusion of 5 μg·kg1·min-1)or an equal volume of saline(CG group)during remifentanil/sevoflurane anesthesia.Anesthesia was induced with midazolam 0.03 mg/kg,fentanyl 2 μg/kg,vecuronium 0.1 mg/kg,and propofol 1 mg/kg-2 mg/kg.The data of hemodynamics and Bispectral index of the electroencephalogram were recorded at following time points:before induction,after induction,intubation,skin incision,abdomen closure and extubation Awakening time and extubation time were recorded.Pain scores,sedation scores and postoperative tramodal consumption were recored as well.Results The VRS in KG group at 10,15 min after extubation were lower than that in CG group (2.3±0.6,2.8±0.8,P＜0.05; 2.8±0.5,3.4±0.5,P＜0.01).The first request for tramadol in CG group was earlier than in KG group (13.5±2.9,9.8±2.5,P＜0.05).Tramadol consumption in PACU of CG group was much more than that of KG group(75±26,131±29,P＜0.01).Conclusions Intraoperative low-dose ketamine infusion could lighten postoperative pain and decrease tramodal consumption.These data suggest that small-dose ketamine could prevent postoperative hyperalgesia induced by clinical concentrations of remifentanil. Key words: Remifentanil; Ketamine; Pain; Tramadol