Accuracy of remifentanil target-controlled infusion system in children

Objective To evaluate the accuracy of remifentanil target-controlled infusion (TCI) system in children.Methods Thirty ASA Ⅰ patients, aged 3-12 yr, weighing 10-40 kg, scheduled for elective ear-nosethroat or urological surgery, were randomly divided into 2 groups with 15 patients in each group:2 ng/ml remifentanil group (group Ⅰ) and 4 ng/ml remifentanil group (group Ⅱ). Anesthesia was induced with iv injection of propofol 2 mg/kg and TCI of remifentanil. Remifentanil was administered with a specific TCI system incorporating the pharmacokinetic parameters of Minto.The target plasma concentrations of remifentanil were set at 2 or 4 ng/ml. Tracheal intubation was facilitated with vecuronium 0.1 mg/kg after the children lost consciousness. The children were mechanically ventilated.Anesthesia was maintained with TCI of remifentanil, iv infusion of propofol and intermittent iv boluses of vecuronium. The target plasma concentration of remifentanil remained unchanged and bispectral index value was maintained at 45-65 or auditory evoked potentials index value ＜ 30 by adusting the infusion rate of propofol.Arterial blood samples were taken at 5, 10, 20, 30, 40, 50 and 60 min after TCI remifentanil was stared for determination of blood remifentanil concentrations by high performance liquid chromatography. Median prediction performance error (MDPE),median absolute performance error (MDAPE) and wobble of remifentanil TCI system were calculated. Results The measured concentrations of remifentanil were significantly higher than the target plasma concentrations in both groups (P＜0.05). The MDPE, MDAPE and wobble were 20.0% , 30.0% and 25.0% respectively in group Ⅰ , and 17.5%, 17.5% and 12.5% respectively in group Ⅱ . TheMDAPE and wobble were significantly decreased in group Ⅱ compared with group Ⅰ(P＜0.05).Conclusion When remifentanil is administered using a specific TCI system incorporating the pharmacokinetic parameters of Minto in children of 3-12 years old, the accuracy is not high. Key words: Child; Piperidines;  Drug delivery system