J. Y. Kim

The optimal dose of remifentanil for intubation during sevoflurane induction without neuromuscular blockade in children

The optimal dose of remifentanil needed to produce successful intubating conditions following inhalation induction of anaesthesia using 5% sevoflurane without the use of neuromuscular blocking drugs, was investigated in 25 children aged 3–10u2003years. Sixty seconds after inhalation induction of anaesthesia using sevoflurane 5% in 100% oxygen, a predetermined dose of remifentanil was injected over 30u2003s. The dose of remifentanil was determined using the modified Dixons up‐and‐down method (0.2u2003μg.kg−1 as a step size). The first patient was tested at 1.0u2003μg.kg−1 remifentanil. Ninety seconds following the bolus administration of remifentanil, the childs trachea was intubated. The optimal bolus dose of remifentanil required for successful tracheal intubation was 0.56 (0.15) μg.kg−1 in 50% of children during inhalation induction using 5% sevoflurane in the absence of neuromuscular blocking drugs. Using probit analysis, the 95% effective dose (ED95) of remifentanil was 0.75u2003μg.kg−1 (95% confidence limits 0.63–1.38u2003μg.kg−1).

The effect of lidocaine on remifentanil-induced cough

This study was performed to investigate the incidence of remifentanil‐induced cough and evaluate the efficacy of lidocaine on its prevention. Five‐hundred patients, aged 18–70u2003years, were randomly allocated into two groups to receive either lidocaine 0.5u2003mg.kg−1 or 0.9% normal saline intravenously 1u2003min before remifentanil administration at a target effect‐site concentration of 4u2003ng.ml−1. Any episode of cough was classified as coughing and graded as mild (1–2), moderate (3–4) or severe (5 or more). We found that the overall incidence of cough was significantly higher in the saline group (69 patients; 27.6%) than that in the lidocaine group (38 patients; 15.2%) (pu2003<u20030.001). The results of logistic regression indicated that age and smoking were associated with remifentanil‐induced cough. This study demonstrated that intravenously administered lidocaine 0.5u2003mg.kg−1 effectively suppresses remifentanil‐induced cough without possible systemic lidocaine toxicity.

Prevention of propofol-induced pain in children: combination of alfentanil and lidocaine vs alfentanil or lidocaine alone

BACKGROUNDnPain from a propofol injection is a common side-effect in paediatric patients. This prospective, randomized, double-blind study evaluated the efficacy of a combined pretreatment of alfentanil with lidocaine on the incidence and severity of propofol injection pain in children.nnnMETHODSnAfter obtaining parental consent, 120 paediatric patients were allocated randomly into one of the three groups (n=40, in each). The patients in the alfentanil group received alfentanil 15 microg kg(-1) 90 s before the propofol injection. The patients in the lidocaine group received propofol 3 mg kg(-1) premixed with lidocaine 0.1% over a 15 s period. The patients in the combination group received both alfentanil and lidocaine.nnnRESULTSnThe incidence of propofol injection pain (severity 2 or more) in the combination group (2.6%) was significantly lower than that in the alfentanil and lidocaine groups (30% and 38.5%, respectively) (P=0.001 and <0.001, respectively). No patient in the combination group complained of moderate or severe pain from propofol injection.nnnCONCLUSIONSnOur study demonstrated that the combination treatment of two different analgesic modalities, alfentanil and lidocaine, could prevent the moderate and severe pain on propofol injection, and reduce the incidence of mild pain compared with each drug alone.

Comparison of positive end-expiratory pressure–induced increase in central venous pressure and passive leg raising to predict fluid responsiveness in patients with atrial fibrillation

BACKGROUNDnPositive end-expiratory pressure (PEEP)-induced increase in central venous pressure (CVP) has been suggested to be a robust indicator of fluid responsiveness, with heart rhythm having minimal influence. We compared the ability of PEEP-induced changes in CVP with passive leg raising (PLR)-induced changes in stroke volume index (SVI) in patients with atrial fibrillation after valvular heart surgery.nnnMETHODSnIn 43 patients with atrial fibrillation after cardiac surgery, PEEP was increased from 0 to 10 cm H2O for 5 min and changes in CVP were assessed. After returning the PEEP to 0 cm H2O, PLR was performed for 5 min and changes in SVI were recorded. Finally, 300 ml of colloid was infused and haemodynamic variables were assessed 5 min after completion of a fluid challenge. Fluid responsiveness was defined as an increase in SVI ≥10% measured by a pulmonary artery catheter.nnnRESULTSnFifteen (35%) patients were fluid responders. There was no correlation between PEEP-induced increases in CVP and changes in SVI after a fluid challenge (β coefficient -0.052, P=0.740), whereas changes in SVI during PLR showed a significant correlation (β coefficient 0.713, P<0.001). The area under the receiver operating characteristic curve of the PEEP-induced increase in CVP and changes in SVI during PLR for fluid responsiveness was 0.556 [95% confidence interval (CI) 0.358-0.753, P=0.549) and 0.771 (95% CI 0.619-0.924, P=0.004), respectively.nnnCONCLUSIONSnA PEEP-induced increase in CVP did not predict fluid responsiveness in patients with atrial fibrillation after cardiac surgery, but increases in SVI during PLR seem to be a valid predictor of fluid responsiveness in this subset of patients.

The median effective dose of dexmedetomidine for laryngeal mask airway insertion with propofol 2.0 mg/kg

Dexmedetomidine can be used as a co‐induction agent to facilitate laryngeal mask airway (LMA) insertion with minimal effect on respiratory function. The purpose of the study was to determine the median effective dose (ED50) of dexmedetomidine to facilitate LMA insertion during anaesthesia induction with propofol 2.0u2009mg/kg without neuromuscular blockade.

Comparison of the incidence and severity of cough after alfentanil and remifentanil injection

Background: Intravenous administration of fentanyl derivatives can induce cough paradoxically. This study examined the incidence and severity of cough after a bolus of alfentanil and remifentanil.

Effect-site concentration of remifentanil for nasotracheal versus orotracheal intubation during target-controlled infusion of propofol.

The concentration of remifentanil required for acceptable nasotracheal intubation in adults after target-controlled infusion (TCI) of propofol without neuromuscular blockade was compared with that required for orotracheal intubation. Twenty-five patients undergoing oral and maxillofacial surgery received nasotracheal intubation and 25 undergoing ear, nose and throat surgery received orotracheal intubation. Anaesthesia was induced with propofol TCI at a target effect-site concentration of 5.0 μg/ml. The 50% and 95% effective concentrations (EC50 and EC95, respectively) for remifentanil, calculated using isotonic regression, were 5.40 and 6.85 ng/ml, respectively, in the orotracheal group and 5.75 and 7.43 ng/ml in the nasotracheal group. The EC50 (± SD) values for remifentanil, calculated using a modified Dixons up-and-down method, were 6.08 ± 0.75 and 5.58 ± 0.75 ng/ml for nasotracheal and orotracheal intubation, respectively. Effect-site remifentanil concentrations did not differ significantly between the two groups of patients. Coadministration of propofol and remifentanil can provide acceptable conditions for nasotracheal intubation without neuromuscular blockade.

Effect‐site concentration of propofol for reduction of remifentanil‐induced cough

This study examined the effectiveness of different propofol infusion target concentrations on cough suppression, during a target‐controlled remifentanil infusion. Four hundred patients were randomly assigned to receive propofol target effect‐site concentrations of 0, 3.0, 4.5, or 6.0u2003μg.ml−1. When the propofol effect‐site concentration reached the target, remifentanil was administered at a target effect‐site concentration of 4.0u2003ng.ml−1. Episodes of cough were recorded over a 2‐min period after remifentanil commencement, and graded as mild (1–2), moderate (3–4), or severe (5 or more). The overall incidence of cough was significantly decreased in by propofol 6.0u2003μg.ml−1 compared with 0 or 3.0u2003μg.ml−1 propofol (pu2003<u20030.001). The incidence of severe cough was significantly lower with propofol 6.0u2003μg.ml−1 compared with 3.0u2003μg.ml−1 (pu2003=u20030.03). A propofol target effect‐site concentration of 6.0u2003μg.ml−1 effectively suppressed remifentanil‐induced cough when remifentanil was administrated at a target effect‐site concentration of 4.0u2003ng.ml−1.

Limited maximal flow rate of target-controlled remifentanil infusion and induced cough.

This study evaluated the effect of limiting maximal infusion‐pump flow rate on suppression of remifentanil‐induced cough during target‐controlled infusion. Two hundred and ten patients were randomly assigned to receive remifentanil at an effect‐site concentration of 4.0u2003ng.ml−1 with maximal flow rate limited to 100 (group R100), 200 (group R200), or 1200u2003ml.h−1 (group R1200). The number of episodes of cough were recorded and graded as mild (1–2), moderate (3–4), or severe (5 or more). The incidence of cough was 2.9% in group R100, 5.7% in group R200 and 25.7% in group R1200. Patients in group R100 and R200 had a significantly lower incidence of cough than those in group R1200 (pu2003<u20030.05). Zero, two and five patients coughed a moderate amount in groups R100, R200 and group R1200, respectively (pu2003<u20030.05). Limiting maximal infusion rate during remifentanil TCI suppressed remifentanil‐induced cough.

Comparison of the Optimal Effect-Site Concentrations of Remifentanil for Preventing Cough during Emergence from Desflurane or Sevoflurane Anaesthesia

OBJECTIVE: To compare the effect-site concentrations of remifentanil target-controlled infusion (TCI) that produced 50% and 95% of the maximal effect (EC50 and EC95, respectively) for preventing cough during emergence from desflurane or sevoflurane anaesthesia, in patients undergoing elective thyroidectomy. METHODS: Adults undergoing elective thyroidectomy were randomized to receive anaesthesia with desflurane or sevoflurane. The EC50 and EC95 values for remifentanil TCI were determined using Dixons up-and-down method and probit analysis with sigmoid curve. RESULTS: In total, 48 patients aged 20 – 64 years were enrolled in the study. The EC50 ± SD of remifentanil TCI, determined by Dixons up-and-down method, were 1.54 ± 0.70 and 1.11 ± 0.24 ng/ml for desflurane and sevoflurane, respectively. The EC95 of remifentanil TCI, analysed by probit analysis, were 2.88 ng/ml and 2.29 ng/ml for desflurane and sevoflurane, respectively. The effect-site concentration of remifentanil TCI for preventing cough during emergence from desflurane anaesthesia was not significantly higher than that observed for sevoflurane. CONCLUSIONS: During emergence from anaesthesia, variations in effect-site concentrations of remifentanil for preventing cough are of limited importance as they do not generate significant differences in results.