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

Combined sedation in pediatric magnetic resonance imaging: determination of median effective dose of intranasal dexmedetomidine combined with oral midazolam

BACKGROUND

The exact median effective dose (ED50) of intranasal dexmedetomidine combined with oral midazolam sedation for magnetic resonance imaging (MRI) examination in children remains unknow and the aim of this study was to determine the ED50 of their combination.

METHODS

This is a prospective dose-finding study. A total of 53 children aged from 2 months to 6 years scheduled for MRI examination from February 2023 to April 2023 were randomly divided into group D (to determine the ED50 of intranasal dexmedetomidine) and group M (to determine the ED50 of oral midazolam). The dosage of dexmedetomidine and midazolam was adjusted according to the modified Dixon's up-and-down method, and the ED50 was calculated with a probit regression approach.

RESULTS

The ED50 of intranasal dexmedetomidine when combined with 0.5 mg∙kg- 1 oral midazolam was 0.39 µg∙kg- 1 [95% confidence interval (CI) 0.30 to 0.46 µg∙kg- 1] while the ED50 of oral midazolam was 0.17 mg∙kg- 1 (95% CI 0.01 to 0.29 mg∙kg- 1) when combined with 1 µg∙kg- 1 intranasal dexmedetomidine. The sedation onset time of children with successful sedation in group D was longer than in group M (30.0[25.0, 38.0]vs 19.5[15.0, 35.0] min, P < 0.05). No other adverse effects were observed in the day and 24 h after medication except one dysphoria.

CONCLUSION

This drug combination sedation regimen appears suitable for children scheduled for MRI examinations, offering a more precise approach to guide the clinical use of sedative drugs in children.

TRIAL REGISTRATION

Chinese Clinical Trial Registry, identifier: ChiCTR2300068611(24/02/2023).

Effect of neuromuscular block on surgical conditions during laparoscopic surgery in neonates and small infants: A randomised controlled trial

BACKGROUND

Neuromuscular block (NMB) is routinely used in paediatric and adult anaesthesia to facilitate endotracheal intubation and optimise surgical conditions. However, there are limited data regarding NMB and optimising the conditions for laparoscopic surgery in neonates and small infants.

OBJECTIVE

The goal of this study was to determine the effect of NMB on the conditions for laparoscopic surgery in neonates and small infants.

DESIGN

A randomised controlled trial.

SETTING

Single-centre Children's Hospital, conducted from November 2021 to December 2022.

PATIENTS

One hundred and two ASA I-II neonates and small infants aged up to 60 weeks postmenstrual age who were scheduled to undergo an elective laparoscopic Ladd's procedure were included in the study.

INTERVENTIONS

Patients were randomised into three groups: no NMB group, shallow NMB group and moderate NMB group. Each group was given different doses of rocuronium to achieve the target depth of NMB.

MAIN OUTCOME MEASURES

The primary outcome was the quality of the surgical conditions evaluated with the Leiden-Surgical Rating Scale (L-SRS) by a blinded surgeon. Secondary outcomes included tracheal intubating conditions and adverse events.

RESULTS

The percentage of L-SRS scores of 4 or 5 was similar among the three groups at all the assessment times ( P  > 0.05 for each time interval). The distribution of L-SRS scores was also similar among the three groups. There were no significant differences in operating condition scores between the groups at any time interval ( P  > 0.05 for each time interval). The incidence of adverse events during anaesthesia induction was significantly higher in the no NMB group (51.4%) than in the other two groups (13.6% and 14.7%) (adjusted P  = 0.012 and adjusted P  = 0.003). In particular, clinically unacceptable intubation conditions occurred in 12 patients (34.3%) in the no NMB group, significantly more than in the shallow NMB group (6.1%, adjusted P  = 0.012) and moderate NMB group (2.9%, adjusted P  = 0.003). There was no statistically significant difference in the incidence of adverse events in the PACU among the three groups ( P  = 0.103).

CONCLUSIONS

The depth of NMB was not associated with superior surgical conditions during laparoscopic surgery, but it was associated with a reduction in adverse events during induction and maintenance of anaesthesia in neonates and small infants.

TRIAL REGISTRATION

Registered at www.chictr.org.cn (ChiCTR2100052296).

Effect of Baricity of Bupivacaine on Median Effective Doses for Motor Block

Background

The median effective dose (ED₅₀) of a drug gives the amount or dose of drug needed to produce effective therapeutic response or desired effect in at least 50% of the population taking it. Our study focused on determining the ED₅₀ required for effective motor block using hyperbaric and plain bupivacaine, and evaluated the influence of baricity on the ED₅₀ required for motor block.

Material/Methods

A total of 38 patients were randomly assigned into 2 groups according to the baricity of bupivacaine: group P received plain bupivacaine and group H received hyperbaric bupivacaine. The patients were administered 0.5% plain or hyperbaric bupivacaine intrathecally. The dosage of anesthetics in each patient was calculated according to the standard up-down sequential allocation method of Dixon. The first patient in each group received a dose of 7.5 mg bupivacaine, and a dose of 1.0 mg was used as the testing interval. The dose was increased or decreased by 1.0 mg for each patient according to the estimated score of motor block.

Results

The ED₅₀ required for effective motor block in spinal anesthesia was 7.20 and 10.05 mg in groups H and P, respectively. Their relative motor blocking potency ratio was found to be 0.72.

Conclusions

The ED₅₀ for motor block was significantly decreased using hyperbaric bupivacaine intrathecally compared with plain bupivacaine, and the baricity of bupivacaine obviously affected the ED₅₀ for the motor block.

The optimal exhaled concentration of sevoflurane for intubation without neuromuscular blockade using clinical bolus doses of remifentanil: A randomized controlled trial

BACKGROUND

The aim of this study was to investigate the optimal exhaled sevoflurane concentration that produces adequate endotracheal intubation conditions when sevoflurane is combined with the different bolus doses of remifentanil used in clinical practice.

METHODS

The patients were randomized to 3 groups (groups 1.0, 1.5, and 2.0), receiving remifentanil bolus doses of 1.0, 1.5, and 2.0 μg/kg, respectively. For each group, the concentration of sevoflurane used for each consecutive patient was increased or decreased using the "up-and-down" method based on the success or failure to achieve adequate conditions for intubation in the previous patient. The remifentanil bolus dose was administered 90 s before intubation and after the target sevoflurane concentration was achieved.

RESULTS

In groups 1.0, 1.5, and 2.0, the effective concentration in 50% (EC50) of the sevoflurane concentration required to perform successful intubation was 3.0, 2.0, and 1.29 vol% and the effective concentration in 95% was 3.45, 2.91, and 1.89 vol%, respectively. When sevoflurane was administered for the induction, the increase in heart rate (HR) of group 1.0 was the highest among the groups. The highest number of adverse events occurred in group 2.0, including vocal cord rigidity, hypotension, and bradycardia.

DISCUSSION

The EC50 of the sevoflurane concentration was 3.0, 2.0, and 1.29 vol% when it was combined with a bolus dose of remifentanil of 1.0, 1.5, and 2.0 μg/kg, respectively. Of the 3 different bolus doses of remifentanil, the dose of 1.5 μg/kg was least associated with changes in the HR/mean blood pressure during intubation without increasing adverse effects.

Median Effective Dose of Intranasal Dexmedetomidine for Rescue Sedation in Pediatric Patients Undergoing Magnetic Resonance Imaging

Background

The median effective dose (ED50) of intranasal dexmedetomidine after failed chloral hydrate sedation has not been described for children. This study aims to determine the ED50 of intranasal dexmedetomidine for rescue sedation in children aged 1 to 36 months, who were inadequately sedated by chloral hydrate administration during magnetic resonance imaging (MRI).

Methods

This study was performed on 120 children, who were 1 to 36 months old and underwent MRI scanning. Intranasal dexmedetomidine was administered as a rescue sedative to children not adequately sedated after the initial oral dose of chloral hydrate (50 mg/kg). Children were stratified into four age groups. ED50 values were estimated from the up-and-down method of Dixon and Massey and probit regression. Other variables included induction time, time to wake up, vital signs, oxygen saturation, MRI scanning time, and recovery characteristics.

Results

ED50 of intranasal dexmedetomidine for rescue sedation was 0.4 μg/kg (95% CI, 0.34 to 0.50) in children aged 1 to 6 months, 0.5 μg/kg (95% CI, 0.48 to 0.56) in children aged 7 to 12 months, 0.9 μg/kg (95% CI, 0.83 to 0.89) in children aged 13 to 24 months, and 1.0 μg/kg (95% CI, 0.94 to 1.07) in children aged 25 to 36 months. There were no significant differences in sedation induction time or time to wake up between the different age groups. Additionally, no significant adverse hemodynamic or hypoxemic effects were noted.

Conclusions

The authors determined the ED50 for rescue sedation using intranasal dexmedetomidine after failed chloral hydrate sedation in children. It was found that ED50 increases with advancing age during the first 3 yr of life.

Comparison of the effects of remifentanil and remifentanil plus lidocaine on intubation conditions in intellectually disabled patients

BACKGROUND AND OBJECTIVES

This is a prospective, randomized, single-blind study. We aimed to compare the tracheal intubation conditions and hemodynamic responses either remifentanil or a combination of remifentanil and lidocaine with sevoflurane induction in the absence of neuromuscular blocking agents.

METHODS

Fifty intellectually disabled, American Society of Anesthesiologists I-II patients who underwent tooth extraction under outpatient general anesthesia were included in this study. Patients were randomized to receive either 2 μg kg(-1) remifentanil (Group 1, n=25) or a combination of 2 μg kg(-1) remifentanil and 1 mg kg(-1) lidocaine (Group 2, n=25). To evaluate intubation conditions, Helbo-Hansen scoring system was used. In patients who scored 2 points or less in all scorings, intubation conditions were considered acceptable, however if any of the scores was greater than 2, intubation conditions were regarded unacceptable. Mean arterial pressure, heart rate and peripheral oxygen saturation (SpO2) were recorded at baseline, after opioid administration, before intubation, and at 1, 3, and 5 min after intubation.

RESULTS

Acceptable intubation parameters were achieved in 24 patients in Group 1 (96%) and in 23 patients in Group 2 (92%). In intra-group comparisons, the heart rate and mean arterial pressure values at all-time points in both groups showed a significant decrease compared to baseline values (p=0.000) CONCLUSION: By the addition of 2 μg/kg remifentanil during sevoflurane induction, successful tracheal intubation can be accomplished without using muscle relaxants in intellectually disabled patients who undergo outpatient dental extraction. Also worth noting, the addition of 1mg/kg lidocaine to 2 μg/kg remifentanil does not provide any additional improvement in the intubation parameters.

Tracheal intubation in intellectually disabled patients: clinical usefulness of remifentanil and sevoflurane without a muscle relaxant

OBJECTIVE

To compare two remifentanil doses (1 µg/kg and 2 µg/kg) in order to determine the preferred dose in intellectually disabled patients undergoing day care dental surgery under sevoflurane-induced general anaesthesia.

METHODS

Patients were randomly assigned to receive either 1 µg/kg (group 1) or 2 µg/kg (group 2) remifentanil; both groups received 8% sevoflurane anaesthesia induction. All other conditions were identical in both groups. Heart rate (HR), mean arterial pressure (MAP) and intubation conditions were assessed.

RESULTS

A total of 27/30 (90.0%) patients in group 1 and 29/30 patients (96.7%) in group 2 had acceptable intubation conditions. Remifentanil administration resulted in significant reductions in HR compared with baseline levels, in both groups. There were no significant between-group differences in HR at any timepoint. MAP decreased significantly compared with baseline in group 2 only.

CONCLUSION

Successful tracheal intubation in intellectually disabled patients can be accomplished with a combination of 1 µg/kg or 2 µg/kg remifentanil and 8% sevoflurane anaesthesia induction, without the requirement for neuromuscular blocking drugs.

[General anaesthesia in children: a French survey of practices]

INTRODUCTION

The practice of pediatric anesthesia requires a regular update of scientific knowledge and technical skills. To provide the most adequate Continuing Medical Education programs, it is necessary to assess the practices of pediatric anesthesiologists. Thus, the objective of this survey was to draw a picture of the current clinical practices of general anesthesia in children, in France.

MATERIAL AND METHODS

One thousand one hundred and fifty questionnaires were given to anesthesiologists involved in pediatric cases. These questionnaires collected information on various aspects of clinical practice relative to induction, maintenance, recovery from general anaesthesia and also classical debated points such as children with Upper Respiratory Infection (URI), emergence agitation, epileptoid signs or anaesthetic management of adenoidectomy. Differences in practices between CHG (general hospital), CHU (teaching hospital), LIBERAL (private) and PSPH (semi-private) hospitals were investigated.

RESULTS

There were 1025 questionnaires completed. Fifty-five percent of responders worked in public hospitals (CHG and CHU); 77% had a practice that was 25% or less of pediatric cases. In children from 3 to 10 years: 72% of respondents used always premedication and two thirds performed inhalation induction in more than 50% of cases. For induction, 53% used sevoflurane (SEVO) at 7 or 8%. Respondents from LIBERAL used higher SEVO concentrations. Tracheal intubation was performed with SEVO alone (37%), SEVO and propofol (55%) and SEVO with myorelaxant (8%), 93% of respondents used a bolus of opioid. For maintenance, the majority of respondents used SEVO associated with sufentanil; desflurane and remifentanil were more frequently used in CHU. Two thirds of respondents used N(2)O. Depth of anesthesia was commonly assessed by hemodynamic changes (52%), end tidal concentration of halogenated (38%) or automated devices based on EEG (7%). In children with URI, 98% of respondents used SEVO for anesthesia. To control the airway 42% used a tracheal tube, 30% a laryngeal mask and 20% a facial mask. Emergence agitation was an important concern for two thirds of respondents, while epileptoid signs were considered as important by only 20%. Eighty-nine percent of respondents practiced anesthesia for adenoidectomy. Anesthesia was induced by inhalation of SEVO 7-8% (41%), 6% (39%) or 4% (12%), 66% put an intravenous line (less frequently in LIBERAL). 67% of the responders managed adenoidectomy without any device to control the airway (more frequently in LIBERAL), 32% administrated a bolus of opioid (less frequently in LIBERAL).

DISCUSSION

This survey demonstrated that the practices regarding general anesthesia in children are relatively homogenous. Most of the differences appeared between LIBERAL and the others structures; the anaesthetic management for adenoidectomy illustrates these findings.

The effect of adjuvant drugs on the quality of tracheal intubation without muscle relaxants in children: a systematic review of randomized trials

Intubation without prior administration of muscle relaxants is a common practice in children. However, succinylcholine may be considered as the golden standard for optimizing intubating conditions. We conducted a systematic review of the literature to identify drug combinations that included induction of anesthesia with sevoflurane or propofol. Our aim was to select drug combinations that yield excellent intubating conditions ≥80%; we identified six combinations in children aged 1-9 years. Sevoflurane with remifentanil (1 or 2 μg·kg(-1) ), lidocaine (2 mg·kg(-1) ), or propofol (2 mg·kg(-1) ) as the adjuvant shared the following characteristics: premedication with midazolam and/or ketamine, long sevoflurane exposure time, high inspired and endtidal sevoflurane concentration, and assisted ventilation. One combination using sevoflurane with propofol (3 mg·kg(-1) ) without premedication, with shorter sevoflurane exposure time, and spontaneous breathing indicated that propofol may be the adjuvant of choice for a rapid sevoflurane induction. The only adjuvant identified in propofol induction was remifentanil (4 μg·kg(-1) ). No serious adverse events were reported with these combinations.

Optimum Bolus dose of Propofol for Tracheal Intubation during Sevoflurane Induction without Neuromuscular Blockade in Children

The purpose of this study was to determine the optimum bolus dose of propofol required to provide excellent conditions for tracheal intubation following inhalational induction of anaesthesia using 5% sevoflurane without neuromuscular blockade. Twenty-eight children, aged three to seven years, requiring anaesthesia for short duration surgery were recruited. Two minutes after beginning the inhalational induction with 5% sevoflurane and 60% nitrous oxide, a predetermined dose of propofol was injected over 10 seconds. Propofol dose was determined using the Dixon's up-and-down method, starting from 3 mg/kg (0.5 mg/kg as a step size). Laryngoscopy was performed 50 seconds after propofol injection. The optimum dose of propofol required for excellent intubating conditions was 1.39±0.37 mg/kg in 50% of children during inhalation induction using 5% sevoflurane and 60% nitrous oxide in the absence of neuromuscular blocking agents. From probit analysis, the 95% effective dose of propofol was 2.33 mg/kg (95% confidence interval 1.78 to 6.21 mg/kg).

The optimal effect-site concentration of remifentanil for lightwand tracheal intubation during propofol induction without muscle relaxation

STUDY OBJECTIVE

To determine the most suitable effect-site concentration of remifentanil during lightwand intubation when administered with a target-controlled infusion (TCI) of propofol at 4.0 μg/mL without neuromuscular blockade.

DESIGN

Prospective study using a modified Dixon's up-and-down method.

SETTING

Operating room of an academic hospital.

PATIENTS

28 ASA physical status 1 and 2 patients, aged 18-65 years, scheduled for minor elective surgery.

INTERVENTIONS

Anesthesia was induced by TCI propofol effect-site concentration to 4.0 μg/mL, and the dose of remifentanil given to each patient was determined by the response of the previously tested patient using 0.2 ng/mL as a step size. The first patient was tested at a target effect-site concentration of 4.0 ng/mL of remifentanil. If intubation was successful, the remifentanil dose was decreased by 0.2 ng/mL; if it failed, the remifentanil dose was increased by 0.2 ng/mL. Successful intubation was defined as excellent or good intubating conditions.

MEASUREMENTS AND MAIN RESULTS

The remifentanil effect-site concentration was measured. The optimal effect-site concentration of remifentanil for lightwand tracheal intubation during propofol induction using 2% propofol target effect-site concentration to 4 μg/mL was 2.16 ± 0.19 ng/mL. From probit analysis, the effect-site concentration of remifentanil required for successful lightwand intubation in 50% (EC50) and 95% (EC95) of adults was 2.11 ng/mL (95% CI 1.16-2.37 ng/mL) and 2.44 ng/mL (95% CI 2.20-3.79 ng/mL), respectively.

CONCLUSION

A remifentanil effect-site concentration of 2.16 ± 0.19 ng/mL given before a propofol effect-site concentration of 4 μg/mL allowed lightwand intubation without muscle relaxant.

Propofol 2 mg/kg is superior to propofol 1 mg/kg for tracheal intubation in children during sevoflurane induction

BACKGROUND

Propofol has been used to facilitate tracheal intubation within a short time of sevoflurane induction without a muscle relaxant in children. We compared as the primary outcome the incidence of excellent intubating conditions after 8% sevoflurane and propofol 1 or 2 mg/kg.

METHODS

One hundred and four patients (2-7 years) were randomly assigned to receive propofol 1 mg/kg in group SP1 (n=53) or propofol 2 mg/kg in group SP2 (n=51) after inhalation induction using sevoflurane 8% in oxygen. Forty-five seconds after propofol and controlled ventilation, intubating conditions were assessed using a four-point scoring system based on ease of laryngoscopy, vocal cords position, coughing, jaw relaxation and limb movement. Heart rate and systolic blood pressure were measured as baseline, after sevoflurane induction, propofol, intubation and at 2 and 5 min following intubation.

RESULTS

Three patients in group SP1 were excluded from analysis. Time from sevoflurane induction to intubation (248.9±71.3 s in group SP1 vs. 230.9±61.3 s in group SP2) and endtidal sevoflurane before intubation (5.6±1.6% in group SP1 vs. 5.2±1.5% in group SP2) did not differ between the two groups. The incidence of excellent intubating conditions was significantly higher in group SP2 compared with group SP1 [47/51 (92%) vs. 28/50 (56%)]. The incidence of acceptable intubating conditions was significantly higher in group SP2 compared with group SP1 [48/51 (94%) vs. 35/50 (70%)]. No hemodynamic difference was noted at any time point between the two groups.

CONCLUSION

Propofol 2 mg/kg during 8% sevoflurane induction resulted in a higher proportion of excellent intubating conditions compared with propofol 1 mg/kg.

Optimal dose of propofol for intubation after sevoflurane inhalation without neuromuscular blocking agent in children

BACKGROUND

This study was designed to determine the optimal dose of propofol for excellent intubating conditions in children without neuromuscular blockade at various alveolar concentrations of sevoflurane.

METHODS

Sixty-three children, aged 0.5-5 years, were randomized to three groups of end-tidal sevoflurane concentration (ETsevo) 3%, 3.5%, and 4%. Inhalation anesthesia was started with sevoflurane 7% in 100% oxygen. When the patients became unconscious, inspired concentration was adjusted to obtain the target ETsevo for each group. When ETsevo reached the target concentration, a predetermined dose of propofol was given and tracheal intubation was performed. The proper dose of propofol was determined using the 'up-and-down' method.

RESULTS

The median dose (95% confidence intervals) of propofol for excellent tracheal intubating conditions in 50% of children were 1.25 mg/kg (0.84-1.75) at ETsevo of 3%, 0.76 mg/kg (0.35-1.21) at 3.5%, and 0.47 mg/kg (0.26-1.09) at 4%. The frequency of adverse effects was not different between groups during induction and recovery.

CONCLUSION

Propofol 1.5-2 mg/kg provides excellent intubating conditions at 3-4% ETsevo in children without using any neuromuscular blocking agent.

Optimum Bolus Dose of Propofol for Tracheal Intubation during Sevoflurane Induction without Neuromuscular Blockade in Children

The purpose of this study was to determine the optimum bolus dose of propofol required to provide excellent conditions for tracheal intubation following inhalational induction of anaesthesia using 5% sevoflurane without neuromuscular blockade. Twenty-eight children, aged three to seven years, requiring anaesthesia for short duration surgery were recruited. Two minutes after beginning the inhalational induction with 5% sevoflurane and 60% nitrous oxide, a predetermined dose of propofol was injected over 10 seconds. Propofol dose was determined using the Dixon's up-and-down method, starting from 3 mg/kg (0.5 mg/kg as a step size). Laryngoscopy was performed 50 seconds after propofol injection. The optimum dose of propofol required for excellent intubating conditions was 1.39±0.37 mg/kg in 50% of children during inhalation induction using 5% sevoflurane and 60% nitrous oxide in the absence of neuromuscular blocking agents. From probit analysis, the 95% effective dose of propofol was 2.33 mg/kg (95% confidence interval 1.78 to 6.21 mg/kg).

Remifentanil in children

Remifentanil has gained the confidence of anesthesiologists and has given a real opportunity to change the way anesthesia is given. It can be considered the ideal opioid despite many obstacles to pediatric use: the condition of 'off-label', the lack of wide randomized clinical trials, and the fear of adverse events because of its high potency. Experiences in the field with this opioid over the years encouraged its use. Use has been associated with N(2)0 and volatile agents for general anesthesia and with propofol for total intravenous anesthesia (TIVA). It seems very useful for sedation inside and outside the operating room and in intensive care for both short painful procedures and synchronization with mechanical ventilation. However, its unique pharmacokinetic characteristics causing rapid onset and offset of effect appear unchanged in small children and even in premature neonates and need to be really confirmed by further pharmacokinetic studies. Moreover, the real risks of tolerance and hyperalgesia should be evaluated in the pediatric population. In this review, we go through the newer aspects of this versatile drug that has been proposed as 'the pediatric anesthetist's opiate'.

The effect of remifentanil on the emergence characteristics of children undergoing FBO for bronchoalveolar lavage with sevoflurane anaesthesia

BACKGROUND AND OBJECTIVE

The aim of this study was to compare the effects of sevoflurane vs. sevoflurane and remifentanil on cough and agitation during emergence and recovery after fiberoptic bronchoscopy.

METHODS

Children between 2 and 6 years of age undergoing fiberoptic bronchoscopy were enrolled. All patients were premedicated with oral midazolam. Patients were randomly assigned to either group S (sevoflurane alone, n = 25) or group SR (sevoflurane with remifetanil, n = 25). Anaesthesia was induced and maintained with sevoflurane in all patients. Group SR received remifentanil at a bolus dose of 1 microg/kg over 2 min followed by a maintenance infusion of 0.15 microg/kg/min. In addition to routine anaesthesia documentation, agitation scores and cough scores were recorded every 5 min during emergence and recovery.

RESULTS

Duration of the procedure, anaesthesia and emergence phases was similar in both groups (P > 0.05). Time until recovery was significantly shorter in group SR than in group S (7.0 +/- 5.5 min and 13.0 +/- 3.5 min, respectively; P = 0.001). Cough scores were not significantly different between the two groups during emergence and recovery (Kruskal-Wallis ANOVA test, P > 0.05). However, the mean agitation score at 5 min in group SR was significantly higher than that in group S (Kruskal-Wallis ANOVA test, P < 0.01). One case of hypoxaemia from thoracic rigidity occurred in a patient in group SR.

CONCLUSION

The addition of remifentanil significantly shortened recovery time in children undergoing fiberoptic bronchoscopy under sevoflurane anaesthesia. In the recovery period, remifentanil did not decrease cough, and increased agitation.

Effect of Remifentanil on Tracheal Intubation Conditions and Haemodynamics in Children Anaesthetised with Sevoflurane and Nitrous Oxide

This study examined the effect of remifentanil added to inhalation agents on intubating conditions in children (aged one to seven years). As is our routine, all patients were premedicated with 0.004 mg/kg glycopyrrolate intramuscularly 30 minutes before anaesthesia to prevent bradycardia and salivary secretion, and received intravenous 1 mg/kg ketamine prior to transfer into the operating room to facilitate separation of the child from the parents. Laryngoscopy was attempted after ventilation with 8% sevoflurane in 50% nitrous oxide and 50% oxygen for two minutes, and intravenous administration of either a placebo bolus of saline (Group S) or one of two doses of remifentanil, 1 μg/kg (Group R1) or 2 μg/kg (Group R2) given over 30 seconds, commenced at the beginning of the sevoflurane administration. Only 18 of 32 patients (56.3%) in Group S had acceptable intubating conditions compared with 31 of 32 patients (96.9%) in Group R1 and 32 of 32 patients (100%) in Group R2 (P <0.001). Mean blood pressure was lower in Group R1 and R2 compared with Group S (P <0.005). Our routine use of ketamine and glycopyrrolate may have influenced the relative lack of significant hypotension and bradycardia. Sevoflurane, nitrous oxide and remifentanil provided acceptable conditions for tracheal intubation in children and could be an acceptable alternative to intravenous induction and neuromuscular blocking agents.

Target-controlled inhalation induction with sevoflurane in children: a prospective pilot study

BACKGROUND

Target-controlled inhalation induction (TCII) with sevoflurane is becoming possible with new anesthesia platforms. Although TCII has already been performed in adults, it remains to be evaluated in children.

METHODS

In a prospective study, we compared TCII using the Felix AInOC anesthetic station (Taema, Anthony, France) to our standard protocol inhalation induction in children scheduled for elective surgery under general anesthesia. After preoxygenation, sevoflurane induction was performed in both groups without priming of the circuit. Sufentanil was administered after venous line placement.

RESULTS

In the TCII group, no overdosage or underdosage was observed except in two children where TCII failed owing to high agitation, and the number of adjustments was lower compared with our standard protocol inhalation induction (1(1-2.5[0-5]) vs 6(5-6[4-10]) respectively). Moreover, the delay to obtain target end-tidal sevoflurane concentration was shorter in the TCII group (2(1.6-2.7[1.3-4]) min vs 3.4(2.5-3.8[2.3-6.5]) min respectively). No significant difference in the delay of loss of consciousness or in the conditions for intubation or laryngeal mask placement was observed between the groups.

CONCLUSION

The Felix AInOC allows TCII to be performed satisfactorily in children. Manual inhalation induction induced a higher number of adjustments and overdosages.

The optimum bolus dose of remifentanil to facilitate laryngeal mask airway insertion with a single standard dose of propofol at induction in children

The purpose of this study was to determine the optimal bolus dose of remifentanil required for the successful insertion of the laryngeal mask airway during propofol induction in children without a neuromuscular blocking agent. Twenty-six paediatric patients, aged 3-10 years, requiring anaesthesia for short ambulatory surgery were recruited. A predetermined bolus dose of remifentanil was injected over 30 s, followed by propofol 2.5 mg.kg(-1) over 10 s. The bolus dose of remifentanil was determined by a modified Dixon's up-and-down method, starting from 0.5 microg.kg(-1) (0.1 microg.kg(-1) as a step size). Laryngeal mask insertion was attempted 90 s after the end of remifentanil injection and the response of patients was classified as either 'movement' or 'no movement'. The bolus dose of remifentanil at which there was a 50% probability of successful laryngeal mask insertion (ED(50)) during induction with 2.5 mg.kg(-1) propofol was 0.56 (0.07) microg.kg(-1) in children without a neuromuscular blocking agent. From probit analysis, the ED(50) and ED(95) of remifentanil were 0.52 microg.kg(-1) (95% confidence limits, 0.42-0.62 microg.kg(-1)) and 0.71 microg.kg(-1) (95% confidence limits, 0.61-1.40 microg.kg(-1)), respectively.