BACKGROUND: Intravenous administration of rocuronium induces intense pain in most patients (60-100%). This could be harmful during anesthesia induction because of the unintended reflex movement of an unconscious patient in response to the pain. Previous studies have reported that remifentanil effectively reduces rocuronium-induced pain and withdrawal movements. This study was designed to evaluate the EC50 and EC95 of remifentanil to prevent withdrawal movements in children. METHODS: We enrolled a total of 171 pediatric patients scheduled for general anesthesia in this study. Remifentanil was administrated by target-controlled infusion. Effect-site target concentrations ranged from 0.5 to 3.0 ng/ml. At each concentration, experiments were repeated in 10-20 patients. Propofol 2 mg/kg and rocuronium 0.9 mg/kg were administrated after equilibration of plasma and effect-site target remifentanil concentration. The withdrawal movements were graded on a 4-point scale. The EC50 and EC95 of remifentanil to prevent rocuronium-induced withdrawal movements were determined by using a logistic regression model. RESULTS: The logistic regression model showed that the probability of preventing rocuronium-induced withdrawal movement was as follows: exp (-3.49 + 2.07 x remifentanil concentration) / (1 + exp [-3.49 + 2.07 x remifentanil concentration]). EC50 and EC95 were 1.69 ng/ml (95% confidence intervals [CIs], 1.42-1.87) and 3.11 ng/ml (95% CIs, 2.79-3.72), respectively. CONCLUSIONS: Administration of remifentanil at an effect-site target concentration of 3.1 ng/ml could effectively prevent rocuronium-induced withdrawal movements.
Administration, Intravenous ; Anesthesia ; Anesthesia, General ; Child* ; Humans ; Logistic Models ; Pediatrics ; Plasma ; Propofol ; Reflex

BACKGROUND: The old age population, including the very old aged (> or = 85 years), is rapidly increasing, and femur neck fracture from accidents is commonly seen in the elderly. Use of bone cement during bipolar hemiarthroplasty can cause bone cement implantation syndrome. METHODS: This study was prospectively conducted on the elderly who were scheduled to undergo elective cemented bipolar hemiarthroplasty under spinal anesthesia. Patients were divided into 2 groups: the old age (65-84 years) and very old age groups (> or = 85 years). Hemodynamic parameters were recorded at the following time points: the start of the operation, femoral reaming, cement insertion, every 2 minutes after cement insertion for 10 minutes, femoral joint reduction, and the end of operation. When hypotension occurred, ephedrine was given. RESULTS: Sixty-five patients in the old age group and 32 patients in the very old age group were enrolled. Mean ages were 78.9 and 89.4 years, respectively, in the old age and very old age groups. The very old age group showed constantly decreased levels of cardiac index and stroke volume from cementing until the end of the operation compared to the old age group. To maintain hemodynamic stability after cement insertion, the requirement of ephedrine was higher in the very old age group than in the old age group (13.52 +/- 7.76 vs 8.65 +/- 6.38 mg, P = 0.001). CONCLUSIONS: Bone cement implantation during bipolar hemiarthroplasty may cause more prominent hemodynamic changes in very elderly patients. Careful hemodynamic monitoring and management are warranted in very elderly patients undergoing cemented bipolar hemiarthroplasty.
Aged ; Anesthesia, Spinal* ; Bone Cements ; Ephedrine ; Femoral Neck Fractures ; Hemiarthroplasty* ; Hemodynamics* ; Humans ; Hypotension ; Joints ; Prospective Studies ; Stroke Volume