Influence of a modified propofol equilibration rate constant (k(e0)) on the effect-site concentration at loss and recovery of consciousness with the Marsh model.

This study compared the predicted effect-site concentration of propofol at loss and recovery of consciousness when using target-controlled infusion devices with the same pharmacokinetic model (Marsh) but a different plasma effect-site equilibration rate constant (ke0 ), the Diprifusor(TM) (ke0 0.26 min(-1) ) and Base Primea™ (ke0 1.21 min(-1) ). We studied 60 female patients undergoing minor gynaecological surgery under general anaesthesia. Although the total dose of propofol and time until loss of consciousness were comparable, the effect-site concentration at loss of consciousness was significantly lower with the Diprifusor than with the Base Primea (1.2 (0.3) µg.ml(-1) vs 4.5 (0.9) µg.ml(-1) , respectively, p < 0.001). The effect-site concentration at recovery of consciousness was significantly higher with the Diprifusor than with the Base Primea (1.8 (0.4) µg.ml(-1) vs 1.5 (0.2) µg.ml(-1) , respectively, p = 0.01). In conclusion, the effect-site concentration of propofol differs depending on the ke0 , despite the use of the same pharmacokinetic model. Therefore, the ke0 should be considered when predicting loss and recovery of consciousness based on the effect-site concentration of propofol.

A short period of inhalation induction with sevoflurane prevents rocuronium-induced withdrawal in children.

BACKGROUND: the aim of this study was to determine whether or not inhalation induction with sevoflurane can prevent the withdrawal movement associated with the injection of rocuronium. METHODS: a total of 75 pediatric patients were randomly allocated to five groups (S 1.5, 2.0, 2.5, 3.0, and the control group). In the control group (n=15), 2.5% thiopental 5 mg/kg was injected intravenously. Rocuronium 0.4 mg/kg was injected immediately after loss of consciousness. In the S 1.5, 2.0, 2.5, or 3.0 group, rocuronium 0.4 mg/kg was injected at 1.5, 2, 2.5, or 3 min after inhalation induction, respectively, and the withdrawal response was recorded. End-tidal sevoflurane concentrations were recorded at the time of the rocuronium injection. The inhalation time of sevoflurane before rocuronium injection required to provide no withdrawal response in 50% and 95% of patients (IT(50) and IT(95) ) was calculated. RESULTS: the incidence of withdrawal was 80% (12/15), 71.4% (10/14), 21% (3/14), 0% (0/14), and 0% (0/15) in group C, group S 1.5, group S 2.0, group S 2.5, and group S 3.0, respectively. IT(50) of the rocuronium injection time was 1.7 min (95% CI: 1.5-1.9) and IT(95) was 2.3 min (95% CI: 2.0- 2.9). CONCLUSIONS: this study demonstrated that inhalation induction with sevoflurane can prevent the withdrawal movement induced by rocuronium in children, and IT(50) and IT(95) for the prevention of movement was 1.7 and 2.3 min, respectively.

Prevention of withdrawal movement associated with injection of rocuronium in children: comparison of remifentanil, alfentanil and fentanyl.

BACKGROUND: We compared the efficacy of remifentanil, alfentanil and fentanyl in reducing withdrawal movement associated with the injection of rocuronium in children. METHODS: In total, 164 ASA physical status I or II pediatric patients, aged 1-14 years, were randomly assigned to four treatment groups: group C received saline; group R, remifentanil 1 microg/kg; group A, alfentanil 10 micro/kg; and group F, fentanyl 2 microg/kg. Treatments were injected over 30 s, followed by thiopental 5 mg/kg. At 90 s after the start of the study drug injection, rocuronium 0.6 mg/kg was injected over 10 s. The patient's response to the injection of rocuronium was graded on a four-point scale in a double-blinded manner. RESULTS: The incidence of withdrawal movement was 89.5% in group C, 70.3% in group F, 36.3% in group A and 7.2% in group R. The incidence of generalized movement (grade 4) was 86.9% in group C, 58.5% in group F, 15.9% in group A and 2.4% in group R. CONCLUSION: Remifentanil, alfentanil and fentanyl all reduced the incidence of withdrawal movement when administered 90 s before the injection of rocuronium compared with saline. Remifentanil was the most effective, followed by alfentanil. Fentanyl was less effective but significantly different from the saline in reducing withdrawal movement in children.