Conditions for laryngeal mask insertion. A comparison of propofol versus sevoflurane with or without alfentanil

A comparison of the time course of action and laryngeal mask airway insertion conditions with different doses of mivacurium for day-case urologic surgery in children: a prospective cohort study

Objective

To investigate the time course of action of different doses of mivacurium and determine the appropriate dose for laryngeal mask airway (LMA) insertion for day-case urologic surgery in children.

Methods

A total of 105 patients who enrolled in this study between March 2021 and December 2021 were randomised into 3 groups: Group A (mivacurium 0.15 mg/kg, n = 35), Group B (mivacurium 0.20 mg/kg, n = 35) and Group C (mivacurium 0.25 mg/kg, n = 35). The different doses of mivacurium were injected before LMA insertion. The primary outcomes included the grading of conditions for the LMA insertion-18 score, onset time, recovery index and the duration that mivacurium was effective. Secondary outcomes included pulse oxygen saturation, mean blood pressure, heart rate and the incidence of adverse events.

Results

The score of the conditions for LMA insertion in Group A was significantly lower than in Groups C and B (p < 0.005). There was a significant difference in the onset time between Groups B and A (p < 0.005). There was no significant difference in the overall incidence of adverse reactions between these groups (p > 0.05).

Conclusion

Anaesthesia with 0.2 mg/kg of mivacurium can effectively shorten the onset time and facilitate insertion of the LMA in children undergoing day-case urologic surgery.

Feasibility and Safety of Remazolam versus Propofol When Inserting Laryngeal Masks Without Muscle Relaxants During Hysteroscopy

Purpose

This study aimed to evaluate the efficacy and safety of remazolam compared with propofol in patients who underwent laryngeal mask airway (LMA) insertion without the use of muscle relaxant agents during hysteroscopic surgery.

Patients and Methods

A total of 72 patients undergoing hysteroscopy with LMA insertion were assigned to two groups. The patients in the remazolam group received 0.3 μg/kg sufentanil, 0.3 mg/kg remazolam and 1.2 mg/kg remifentanil, whereas the patients in the propofol group received 0.3 μg/kg sufentanil, 2.0 mg/kg propofol and 1.2 mg/kg remifentanil for insertion of the LMA. The primary endpoint was the summed score of the insertion conditions. The secondary endpoints included hemodynamics, the duration of induction, the duration of insertion, tidal volume, plateau pressure and adverse events.

Results

No difference was identified between the propofol group and remazolam group in the median summed score [18.0 (18.0, 18.0), 18.0 (17.0, 18.0), respectively, P > 0.05]. The induction duration was significantly longer (P < 0.05) in the remazolam group than propofol group. The cost of dopamine (P < 0.05) was significantly lower in the remazolam group compared with the patients in the propofol group, while the plateau pressure (P < 0.05) and the incidence of transient mild laryngospasm (P < 0.05) were significantly higher in the remazolam group. No differences were identified between the two groups in terms of heart rate, tidal volume, injection pain or hiccups (P > 0.05).

Conclusion

Remazolam provided similar insertion conditions and better hemodynamic stability than propofol during LMA insertion without the use of muscle relaxant agents. However, a higher incidence of transient mild laryngospasm was found in the remazolam group, which should be considered.

Comparison of thiopentone with lidocaine spray vs propofol for laryngeal mask airway insertion at tikur anbessa specialized hospital. A prospective cohort study

Background

Insertion of laryngeal mask airway (LMA) requires an adequate depth of anesthesia. Optimal insertion conditions and hemodynamic stability during LMA insertion are mainly influenced by the choice of the intravenous induction agent. Propofol was recommended as a standard induction agent for LMA insertion. Due to unavailability and cost for treatment Propofol is not easily availed, thus this study aimed at assessing the effect of thiopentone with lidocaine spray compared to Propofol on hemodynamic change and LMA insertion on the patient undergoing elective surgery.

Methods

Eighty-four participants were followed in a prospective cohort study based on the induction type of either thiopentone-lidocaine group (TL) or Propofol (P). Hemodynamic variables, LMA insertion condition, apneic time, and cost of treatment during the perioperative time were recorded. Data were checked for normality using the Shapiro-Wilk test. Numeric data were analyzed unpaired student's t-test or Manny Whitney test. Categorical data were analyzed by the chi-square test. A p-value ≤ 0.05 was considered a statistically significant difference.

Result

The comparison of data showed that a significant reduction in mean arterial blood pressure (MAP) in the Propofol group during the first 10 min. The MAP at first minute after LMA insertion was 78.4 ± 5.5 in the Propofol group compared to 81.8 ± 5.6 in thiopentone-lidocaine group p < 0.001. the mean MAP at 5th and 10th minutes after LMA insertion is also significantly lower in the Propofol group compared to the thiopentone-lidocaine group, p < 0.05. There were no statistically significant differences regarding the heart rate change and insertion conditions between the two groups. Mean apneic time was 138 ± 45.8 s in the Propofol group and 85 ± 13.8 s in thiopentone-lidocaine group p < 0.001. Thiopentone-lidocaine group had a lower treatment cost compared to the Propofol group.

Conclusion

Thiopentone with 10% topical Lignocaine is an alternative for the insertion of LMA to Propofol, with better hemodynamic stability and cost-effectiveness.

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Insertion of laryngeal mask airway requires an adequate depth of anesthesia.

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The choice of induction agent influence the optimal insertion conditions of LMA.

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The hemodynamic stability can also be affected by types of induction agent.

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Thiopentone with 10% topical Lignocaine is an alternative for the insertion of LMA.

The median effective dose (ED50) of cis-Atracurium for laryngeal mask airway insertion during general Anaesthesia for patients undergoing urinary surgery

Background

In clinical practice, the laryngeal mask airway is an easy-to-use supraglottic airway device. However, the cis-atracurium dosage for laryngeal mask insertion has not been standardised. We aimed to determine the optimal dose of cis-atracurium using a sequential method for successful laryngeal mask insertion.

Methods

The cohort study protocol is registered at clinicaltrial.gov (NCT-03668262). Twenty-three patients undergoing elective urinary surgery were sequentially administered cis-atracurium doses as follows: 150, 100, 70, 50, 30, and 20 μg·kg^− 1. The main outcome involved the determination of the response to laryngeal mask airway insertion: ≥16 points and < 16 points indicated “satisfactory” and “unsatisfactory” responses, respectively. The median effective dose was estimated using the mean of the seven crossovers from “satisfactory” and “unsatisfactory” responses. The primary outcome involved the determination of the median effective dose (ED50) of cis-atracurium for laryngeal mask airway insertion.

Results

The median effective dose of cis-atracurium was 26.5 μg·kg^− 1 (95% CI 23.6–29.8) using the sequential method. Heart rate was decreased in the 50 μg·kg^− 1 group compared to that in the 30 μg·kg^− 1 group at timepoints T7, T8, and T10 (P = 0.0482, P = 0.0460, and P = 0.0236, respectively), but no difference was observed in the 20 μg·kg^− 1 group. Systolic blood pressure was decreased in the 50 μg·kg^− 1 group compared to that in the 20 μg·kg^− 1 group at timepoints T2, T3, and T4 (P = 0.0159, P = 0.0233, and P = 0.0428, respectively). The train-of-four value was significantly lower in the 50 μg·kg^− 1 group than in the 30 μg·kg^− 1 group at timepoint T3 (P = 0.0326).

Conclusions

The ED50 of cis-atracurium was 26.5 μg·kg^− 1 for laryngeal mask airway insertion.

Trial registration

Clinicaltrial.gov Registry, NCT03668262, Registered on 11 September 2018.

Supreme™ laryngeal mask airway insertion requires a lower concentration of sevoflurane than ProSeal™ laryngeal mask airway insertion during target-controlled remifentanil infusion: a prospective randomised controlled study

Background

ProSeal (PLMA) and Supreme (SLMA) laryngeal mask airways are effective ventilator devices with distinctive designs that may require different anaesthetics for insertion. Sevoflurane induction provides acceptable conditions for laryngeal mask insertion, and remifentanil significantly decreases the minimum alveolar concentration of sevoflurane required for that insertion. The study aimed to evaluate the optimal end-tidal (ET) sevoflurane concentration for successful insertion of PLMA versus SLMA in patients receiving a remifentanil infusion without a neuromuscular blocking agent.

Methods

Altogether, 45 patients ASA (American Society Anaesthesiologists) physical status I–II, aged 18–60 years were scheduled for elective ambulatory surgery. Exclusion criteria were a difficult airway, recent respiratory infection, reactive airway, obstructive sleep apnoea syndrome, gastric aspiration’s risk factors, pregnancy, and lactation. Patients were randomly allocated to receive the SLMA or the PLMA. Sevoflurane induction with co-administration of remifentanil was performed at an effect-site concentration of 4 ng mL^− 1. ET₅₀ was calculated with a modified Dixon’s up-and-down method (starting at 2.5% in steps of 0.5%). Predetermined sevoflurane concentration was kept constant during the 10 min before LMA insertion. Patient’s response to LMA insertion was classified as “movement” or “no movement”. Sevoflurane ET₅₀ was determined as the midpoint concentration of all the independent pairs that manifested crossover from “movement” to “no movement”.

Results

The ET₅₀ sevoflurane concentration co-administered with remifentanil required for PLMA insertion was 1.20 ± 0.41% (95% confidence interval 0.76 to 1.63%). For SLMA insertion, it was 0.55 ± 0.38% (95% confidence interval 0.14 to 0.95%) (p = 0.019).

Conclusions

The end-tidal sevoflurane concentration with co-administered remifentanil required to allow insertion of the SLMA was 54% lower than that needed for inserting the PLMA.

Trial registration

Clinicaltrials.gov identifier: NCT03003377. Retrospectively registered. Date of registration: December 28, 2016.

A feasibility study of jaw thrust as an indicator assessing adequate depth of anesthesia for insertion of supraglottic airway device in morbidly obese patients

Background:

Jaw thrust has been proven as a useful test determining adequate depth of anesthesia for successful insertion of supraglottic airway device (SAD) in normal adults and children receiving intra-venous or inhalational anesthesia induction. This prospective observational study aimed to determine the feasibility and validity of this test when using as an indicator assessing adequate depth of anesthesia for successful insertion of SAD in spontaneously breathing morbidly obese patients receiving sevoflurane inhalational induction.

Methods:

Thirty morbidly obese patients with a body mass index 40 to 73 kg/m² undergoing bariatric surgery in Beijing Friendship Hospital from October 2018 to January 2019 were included in this study. After adequate pre-oxygenation, 5% sevoflurane was inhaled and inhalational concentration of sevoflurane was increased by 1% every 2 min. After motor responses to jaw thrust disappeared, a SAD was inserted and insertion conditions were graded. The anatomic position of SAD was assessed using a fiberoptic bronchoscope.

Results:

The SAD was successfully inserted at the first attempt in all patients. Insertion conditions of SAD were excellent in nine patients (30%) and good in 21 patients (70%), respectively. The fiberoptic views of SAD position were adequate in 28 patients (93%).

Conclusions:

Jaw thrust test is a reliable indicator determining adequate anesthesia depth of sevoflurane inhalational induction for successful insertion of SAD in spontaneously breathing morbidly obese patients.

Clinical trial registration:

ChiCTR1800016868; http://www.chictr.org.cn/showproj.aspx?proj=28646.

Randomized Double-blind Comparison of Ketamine-Propofol, Fentanyl-Propofol and Propofol-Saline on Haemodynamics and Laryngeal Mask Airway Insertion Conditions

The aim of this prospective, double-blind, randomized, placebo-controlled clinical trial was to investigate whether the administration of ketamine before induction with propofol improves its associated haemodynamic profile and laryngeal mask airway (LMA) insertion conditions. Ninety adult patients were randomly allocated to receive either ketamine 0.5 mg.kg-1 (n=30), fentanyl 1 μg.kg-1 (n=30) or normal saline (n=30), before induction of anaesthesia with propofol 2.5 mg.kg-1. Insertion of the LMA was performed 60s after injection of propofol. Arterial blood pressure and heart rate were measured before induction (baseline), immediately after induction, immediately before LMA insertion, immediately after LMA insertion and every minute for three minutes after LMA insertion. Following LMA insertion, the following six subjective endpoints were graded by a blinded anaesthestist using ordinal scales graded 1 to 3: mouth opening, gagging, swallowing, movement, laryngospasm and ease of insertion. Systolic blood pressure was significantly higher following ketamine than either fentanyl (P=0.010) or saline (P=0.0001). The median (interquartile range) summed score describing the overall insertion conditions were similar in the ketamine [median 7.0, interquartile range (6.0–8.0)] and fentanyl groups [median 7.0, interquartile range (6.0–8.0)]. Both appeared significantly better than the saline group [median 8.0, interquartile range (6.75–9.25); P=0.024]. The incidence of prolonged apnoea (>120s) was higher in the fentanyl group [23.1% (7/30)] compared with the ketamine [6.3% (2/30)] and saline groups [3.3% (1/30)]. We conclude that the addition of ketamine 0.5 mg.kg–1 improves haemo-dynamics when compared to fentanyl 1 μg.kg–1, with less prolonged apnoea, and is associated with better LMA insertion conditions than placebo (saline).

Entropy as an Indicator to Measure Depth of Anaesthesia for Laryngeal Mask Airway (LMA) Insertion during Sevoflurane and Propofol Anaesthesia

INTRODUCTION

Assessment of the depth of anaesthesia is fundamental to the anaesthetic practice. Entropy measurement is an objective monitoring and is of two types- Response Entropy (RE) and State Entropy (SE) indicating analgesic and hypnotic levels during general anaesthesia.

AIM

The aim of our study was to assess the depth of anaesthesia for LMA placement using entropy as a tool. The assessment of entropy as an indicator of depth of anaesthesia in the form of haemodynamic variations and success rate of LMA placement.

MATERIALS AND METHODS

A prospective study was carried out after ethical committee approval in 100 patients, aged 20-50 years, with ASA grade I and II of either gender undergoing elective surgery lasting less than two hours under general anaesthesia. Anaesthesia was induced with sevoflurane 2.5% and IV propofol at 6 ml/min until entropy value fell from baseline values to 30-40 and then LMA insertion was performed. SE and RE values were noted every 30 seconds for five minutes. Mean blood pressure and heart rate were recorded every minute after induction for 5 minutes.

RESULTS

There was a significant change in RE and SE values within 30 seconds from start of induction. Desired values of RE (40.10±2.52) and SE (39.2±2.47) were achieved at 120 seconds to 150 seconds. Mean dose of propofol used during surgery was 86.5±3.5 mg and mean insertion time was 110±12 seconds Patients in study group had a stable haemodynamics throughout the procedure, (p-value -0.8).

CONCLUSION

Entropy is a reliable indicator to assess depth of anaesthesia for LMA placement during sevoflurane and propofol anaesthesia.

Comparison of sevoflurane and propofol for laryngeal mask airway insertion and pressor response in patients undergoing gynecological procedures

Background and Aims:

A popular method of providing anesthesia for laryngeal mask airway (LMA) insertion is with the use of propofol. However, bolus propofol has been associated with adverse effects such as hypotension, apnea and pain on injection. Hence, time is needed to search an alternative. We aimed to compare the induction characteristics, ease of LMA insertion, hemodynamic changes and complications with inhalation of 8% sevoflurane vital capacity breath and propofol.

Material and Methods:

A prospective randomized study of 60 American Society of Anesthesiologists' Grade I and II patients was conducted and distributed among two groups with 30 each undergoing gynecological procedures under general anesthesia. Group P received the injection propofol and Group S received sevoflurane. At the end point of induction, the LMA insertion was attempted. Scoring systems were used to grade the conditions for insertion of the LMA. Induction, LMA insertion characteristics, hemodynamic changes, complications were assessed. Data were recorded and analyzed. Comparison among the study groups was done with unpaired t-test, Mann–Whitney test and Chi-square test.

Results:

Sevoflurane took a longer time for induction and for LMA insertion than propofol. There was no statistically significant difference between the two groups, with respect to LMA insertion characteristics, heart rate, mean arterial pressure. It is concluded that sevoflurane is associated with good hemodynamic stability and may prove useful incases where propofol is to be avoided. However, the ease of insertion provided with propofol is better.

Estimation of effect-site concentration of propofol for laryngeal mask airway insertion using fentanyl or morphine as adjuvant

BACKGROUND AND AIMS

Insertion of laryngeal mask airway (LMA) requires adequate depth of anaesthesia, which provides jaw relaxation and suppression of upper airway reflexes. Propofol can provide these conditions especially when combined with narcotics. This study had been designed to find out the effect-site concentration (EC50) of propofol using target controlled infusion (TCI) when fentanyl or morphine is added as an adjuvant.

METHODS

Patients satisfying inclusion criteria were divided into fentanyl and morphine groups. Intravenous glycopyrrolate 0.2 mg was given 15 min before induction. Patients were given either intravenous fentanyl (1 μg/kg) or morphine (0.1 mg/kg) before propofol infusion depending on the group. Patients in either groups were induced by continuous infusion of propofol at an EC of 6 μg/mL by TCI with Schneider pharmacokinetic model. The LMA supreme of appropriate size was inserted 1 min after achieving target concentration. Patient movement at LMA insertion or within 1 min of insertion was classified as failure. For subsequent patients, the target EC was increased/decreased depending on previous patients' response. Dixons up and down method was used to determine the EC50. The EC50 is defined as the mean of crossover midpoints in each pair of failure to success.

RESULTS

The EC50 of propofol in the fentanyl group for LMA insertion was 5.95 ± 0.6 μg/ml and morphine group was 5.75 ± 0.8 μg/ml. No significant difference in insertion conditions was noticed between the two groups (P = 0.3).

CONCLUSION

We conclude that there was no significant difference in propofol EC50 for insertion of LMA and insertion conditions were similar when fentanyl or morphine was used as an adjuvant drug.

The effective bolus dose of remifentanil to facilitate laryngeal mask airway insertion during inhalation induction of sevoflurane in children

PURPOSE

The additional administration of remifentanil during inhalation induction with sevoflurane could provide better conditions for laryngeal mask airway (LMA) insertion than sevoflurane alone. This study was designed to evaluate the 50 % effective bolus dose (ED50) and 95 % effective bolus dose (ED95) of remifentanil required for LMA insertion in children during inhalation induction with sevoflurane.

METHODS

Pediatric patients aged 3-12 years requiring general anesthesia were recruited. A predetermined dose of remifentanil was injected over 30 s after the induction of general anesthesia with sevoflurane. LMA insertion was attempted 60 s after remifentanil injection. The dose of remifentanil was determined using the Dixon's up-and-down method, starting from 0.5 μg/kg (step size of 0.05 μg/kg).

RESULTS

The study was conducted until seven cross-over points and 29 children were collected. The ED50 of remifentanil for successful LMA insertion during sevoflurane inhalation induction in children was 0.168 ± 0.035 μg/kg using Dixon's method. In addition, the ED50 and ED95 of remifentanil from the probit analysis were 0.176 μg/kg (95 % confidence limits, 0.102-0.216 μg/kg) and 0.268 μg/kg (95 % confidence limits, 0.223-0.659 μg/kg), respectively.

CONCLUSION

The ED50 and ED95 of remifentanil for successful LMA insertion in children were estimated to be 0.176 (0.168) and 0.268 μg/kg during inhalation induction with 2.1 % sevoflurane.

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

BACKGROUND

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 2.0 mg/kg without neuromuscular blockade.

METHODS

Twenty-two patients, whose American Society of Anesthesiologists physical status was I or II with ages between 18 and 60 years undergoing minor orthopaedic or gynaecological surgery, were enrolled. After an injection of pre-determined bolus dose of dexmedetomidine over 2 min, anaesthesia was induced with propofol 2.0 mg/kg. The modified Dixon's up-and-down method was used to determine the bolus dose of dexmedetomidine, starting from 0.5 μg/kg (step size; 0.1 μg/kg). LMA insertion was conducted 90 s after the propofol injection, and the response of patients was categorized as either 'success' or 'failure.'

RESULTS

Insertion of the LMA was unsuccessful in 12 of 22 patients. The ED50 (95% confidence interval) of dexmedetomidine for successful LMA insertion with propofol 2.0 mg/kg was 0.55 (0.44-0.66) μg/kg. Bradycardia occurred in four patients, and seven patients had an apneic episode.

CONCLUSION

The single dose of dexmedetomidine for successful LMA insertion to be feasible in 50% of patients was 0.55 μg/kg during anaesthesia induction with propofol 2 mg/kg.

The optimal effect-site concentration of sufentanil for laryngeal mask insertion during induction with target-controlled propofol infusion at 4.0 μg/mL

Objective:

The objective of this study is to determine the optimal effect-site concentration (Ce) of sufentanil for satisfactory insertion of laryngeal mask airway (LMA) when administered with a target-controlled infusion (TCI) of propofol at 4.0 μg/mL.

Materials and Methods:

A total of 25 adult patients scheduled for minor elective surgery were enrolled in this study. All patients received induction with a combination of propofol and sufentanil TCI. The TCI of sufentanil was started at a target Ce of 0.1 ng/mL. After equilibrium with the plasma concentration, the TCI of propofol was initiated, targeting a preset Ce of 4.0 μg/mL. After the loss of consciousness, LMA was inserted and assessed by an experienced Anesthesiologist. The Ce of sufentanil for the next patient was guided by modified Dixon's up-and-down method using 0.05 ng/mL as a step size. The Ce of sufentanil required for successful LMA insertion in 50% of adults (EC50) was determined by calculating the midpoint concentration of all independent pairs of patients after at least seven crossover points.

Results:

The optimal Ce (EC50) of sufentanil for LMA insertion during propofol induction using target Ce of 4 μg/mL was 0.16 ng/mL (95% confidence interval [CI] = 0.12-0.20). There was a significant reduction in propofol induced pain score P = 0.0275 and insignificant hemodynamic changes.

Conclusion:

Ce of sufentanil required for successful LMA insertion in 50% of patients (EC50) using propofol target Ce of 4.0 μg/mL was 0.16 ng/mL (95% CI = 0.12-0.20) with a significant reduction in the propofol induced pain and hemodynamic stability.

Target-controlled infusion of remifentanil for laryngeal mask airway insertion during sevoflurane induction in adults

OBJECTIVE

This randomized, double-blind study investigated the suitable target effect-site concentration of remifentanil for laryngeal mask airway (LMA) insertion during inhalation induction with sevoflurane.

METHODS

Patients aged 18 - 60 years were randomly assigned to one of three groups receiving infusions of normal saline (control group), or infusions with target effect-site remifentanil concentrations of either 1 ng/ml (R1 group) or 2 ng/ml (R2 group), 1 min after the induction of anaesthesia with sevoflurane. LMA insertion was attempted 2 min after induction. Insertion conditions were graded using a six-variable, three-point scale (excellent, intermediate or poor).

RESULTS

A total of 102 patients were included. The proportion of patients ranked as excellent for the LMA insertion was significantly higher in groups R1 and R2 compared with the control group. The incidence of apnoea was significantly more frequent in the R2 group than in the control or R1 groups.

CONCLUSIONS

Compared with 1 ng/ml remifentanil or normal saline, target-controlled infusion of 2 ng/ml remifentanil significantly improved the LMA insertion conditions during sevoflurane inhalational induction, although apnoeic episodes were more frequently observed.

Effects of addition of ketamine, fentanyl and saline with Propofol induction on hemodynamics and laryngeal mask airway insertion conditions in oral clonidine premedicated children

Background:

The aim of this double-blind, prospective, randomized, controlled study was to compare the effect of addition of ketamine; fentanyl and saline with propofol anesthesia on hemodynamic profile and laryngeal mask airway (LMA) insertion conditions in oral clonidine premedicated children.

Methods:

180 children (age 2 - 10 years) were at first given oral clonidine (4 μg/kg) 90 minutes before operation, and then were randomly allocated to receive either ketamine 0.5 mg/kg (n=60), fentanyl 1 μg/kg (n=60) or 0.9% normal saline (n=60) before induction with propofol 3.0 mg/kg. Insertion of LMA was performed within 1 minute of injection of propofol. Heart rate and mean blood pressure were noted 1 min before induction (baseline), immediately after induction, before and after insertion of LMA for up to 3 min. Following LMA insertion, 6 subjective end points were noted-mouth opening, coughing, swallowing, patient's movement, laryngospasm, and ease of an insertion. LMA insertion summed score was prepared depending upon these variables.

Results:

LMA insertion summed score was nearly similar in ketamine and fentanyl group, which were significantly better than saline group (P<0.004). Mean blood pressure and heart rate were maintained in ketamine than with fentanyl or saline group. Incidence of prolonged apnea (>120 secs.) was higher in fentanyl group compared to ketamine and saline group.

Conclusion:

Even in oral clonidine premedicated children, addition of ketamine with propofol provides hemodynamic stability and comparable conditions for LMA insertion like fentanyl propofol with significantly less prolonged apnea.

The effects of a single bolus of remifentanil on corrected QT interval change during sevoflurane induction

PURPOSE

Opioids may affect changes in the corrected QT interval (QTc) during anesthetic induction. This study examine whether a single bolus of remifentanil would prolong QTc after laryngeal mask airway (LMA) insertion during sevoflurane induction.

MATERIALS AND METHODS

Forty women of American Society of Anesthesiologists physical status 1 (ASA PS1) undergoing gynecological surgery were studied. All patients were induced using three vital capacity inhalation inductions with 5% sevoflurane. Two minutes after induction, the inspiratory concentration of sevoflurane was reduced to 2%. Using double-blinded randomization, patients were allocated into one of two groups, receiving either saline (placebo group, n = 20) or 0.25 μg.kg⁻¹ remifentanil (remifentanil group, n = 20) over a period of thirty seconds. Sixty seconds later, LMA insertion was performed. Recordings were taken with a 12-lead electrocardiogram at baseline, 2 min after induction and 1 and 3 min after LMA insertion. QTc was calculated by Bazett's formula. The mean arterial pressure (MAP) and heart rate (HR) were also measured at each time point.

RESULTS

The QTc interval was significantly prolonged in the placebo group as compared to the remifentanil group at 1 min after LMA insertion (467.8 ± 16.5 vs. 442.7 ± 21.3 ms, p < 0.001). However, there was no significant difference in QTc at 3 min after LMA insertion between the two groups. MAP and HR were significantly higher in the placebo group (p < 0.001).

CONCLUSION

A single bolus of remifentanil is safe method to attenuate prolonged QTc associated with insertion of LMA.

Fentanyl dosage and timing when inserting the laryngeal mask airway

The study objective was to show that fentanyl given five minutes prior to induction improved insertion conditions for the Classic Laryngeal Mask Airway. Previous work had shown fentanyl at 90 seconds to be unpredictable. A probit analysis design was used in which success/failure rates of different doses of fentanyl were measured and dose-response curves drawn from which the ED50 and ED95 with 95% confidence intervals were determined. Adult Chinese patients with American Society of Anesthesiologists physical status classification I or II and requiring anaesthesia for minor surgery with a laryngeal mask were recruited. They were randomly assigned to one of six dosage groups: 0.25, 0.5, 1.0, 1.5, 2.0 and 3.0 microg x kg1. Fentanyl was given prior to propofol 25 mg x kg(-1), and insertion was assessed 90 seconds later using six categories of patient response. Ninety-six patients, aged 18 to 63 years, were studied. The six dosage groups were similar As the fentanyl dose increased, fewer patients responded to insertion (P < 0.01). Dose-responses could be predicted for all categories, except resistance to insertion and laryngospasm. Probit analysis predicted an ED50 of 0.5 microg x kg(-1) and ED, of 7.5 microg x kg(-1) for ideal insertion conditions (i.e., no swallowing, gagging, body movement or laryngospasm). Commonly used fentanyl doses of 1 to 2 microg x kg(-1) only prevented patients responding to insertion in 70 to 80% of cases. When using propofol 2.5 mg x kg(-1), administering fentanyl five minutes before laryngeal mask insertion does not provide ideal insertion conditions in 95% of cases unless excessively large doses are used. An ideal dose of fentanyl that produces optimum insertion conditions could not be determined.

Fentanyl dose for the Insertion of Classic™ Laryngeal Mask Airways in Non-Paralysed Patients Induced with Propofol 2.5 mg/kg

The aim of this randomised, controlled trial was to determine the optimum dose of fentanyl in combination with propofol 2.5 mg.kg-1 when inserting the Classic™ Laryngeal Mask Airway.

Seventy-five ASA I or II patients were randomly assigned to five groups of fentanyl dosage: 0 μg.kg-1 (placebo), 0.5 μg.kg-1, 1.0 μg.kg-1, 1.5 μg.kg-1 and 2.0 μg.kg-1 Anaesthesia was induced by first injecting the study drug over 10 seconds. Three minutes after the study drug was injected, propofol (2.5 mg.kg-1) was injected over 10 seconds. The Classic™ Laryngeal Mask Airway was inserted four minutes and 30 seconds after injection of the study drug. Insertion conditions were evaluated using a four-category score.

Thirty-nine males and 36 females aged 19 to 59 years were studied. The incidence of prolonged apnoea increased as fentanyl dose increased. We found that there was a high rate of successful first attempt at insertion with 1 μg.kg-1 and 1.5 μg.kg-1, 93% and 87% respectively, compared to 87% in the 2.0 μg.kg-1 group. The 1.0 μg.kg-1 group also achieved an 80% optimal insertion conditions score of 4, compared to 73% in the 1.5 μg.kg-1 group and 80% in the 2 μg.kg-1 group. Therefore we recommend 1.0 pg.kg-1 as the optimal dose of fentanyl when used in addition to propofol 2.5 mg/kg for the insertion of the Classic™ Laryngeal Mask Airway.

Low-dose fentanyl-midazolam combination improves sevoflurane induction in adults

PURPOSE

We investigated the effects of a combination of low-dose fentanyl-midazolam premedication on the speed of inhaled induction with sevoflurane and ProSeal laryngeal mask airway (PLMA) insertion conditions.

METHODS

Eighty adult patients undergoing elective surgery were randomized in a double-blind fashion to receive either a normal saline placebo (Group PLAC) or a fentanyl 0.6 microg x kg(-1) and midazolam 9 microg x kg(-1) premedication (Group FM) 5 min before tidal volume sevoflurane 8%/O(2) induction. Anxiety levels, times to loss of eyelash reflex (LER) and PLMA insertion, and cardiorespiratory data were recorded.

RESULTS

Times to LER (Group PLAC: 66 +/- 34 sec vs Group FM: 47 +/- 18 sec, P = 0.0027, difference = 19 sec: 95% confidence interval [CI] 7-31 sec) and to PLMA insertion (Group PLAC: 186 +/- 80 sec vs Group FM: 119 +/- 44 sec, P < 0.0001, difference = 68 sec: 95% CI 39-97 sec) were shorter following FM. After PLMA insertion, end-tidal sevoflurane concentration (EtSevo) was lower and end-tidal CO(2) (EtCO(2)) was higher following FM. Respiratory rate (RR) was lower with FM, but there was no difference regarding tidal volume. Adverse events, such as movements and apnea, occurred more often in Group PLAC. Systolic blood pressure (SBP) and heart rate (HR) during induction were both lower with FM. Anxiety level after premedication was lower following FM administration. All participants remembered the face mask being applied in Group PLAC vs 69% in Group FM, P < 0.0001.

CONCLUSION

Administration of a low-dose fentanyl-midazolam combination prior to sevoflurane induction decreases time to LER and allows for more rapid and less eventful PLMA insertion. Both SBP and HR were lower when premedication was administered. Patients receiving premedication were less anxious and less likely to remember the face mask. However, premedication was associated with a lower RR and increased EtCO(2) values following PLMA insertion, in spite of lower EtSevo concentrations. (ClinicalTrials.gov ID NCT00723164).

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.

The optimal bolus dose of alfentanil for tracheal intubation during sevoflurane induction without neuromuscular blockade in day-case anaesthesia

BACKGROUND

The purpose of this study was to determine the optimal bolus dose of alfentanil required to provide successful intubating conditions following inhalation induction of anaesthesia using 5% sevoflurane and 60% nitrous oxide without neuromuscular blockade in adult day-case anaesthesia.

METHODS

Twenty-four adults, aged 18-60 years, undergoing general anaesthesia for short ambulatory surgery were enroled into the study. After vital capacity induction, with sevoflurane 5% and 60% nitrous oxide in oxygen, pre-determined dose of alfentanil was injected over 30 s. The dose of alfentanil was determined by modified Dixon's up-and-down method (2 microg/kg as a step size). Ninety seconds after the end of bolus administration of alfentanil, the trachea was intubated. Systolic blood pressure, heart rate and SpO2 were recorded at anaesthetic induction, before, 1 min and 3 min after intubation.

RESULTS

The bolus dose of alfentanil for successful tracheal intubation was 10.7+/-2.1 microg/kg in 50% of patients during inhalation induction. From probit analysis, 50% effective dose (ED(50)) and ED(95) values (95% confidence limits) of alfentanil were 10.7 microg/kg (8.0-12.9 microg/kg) and 14.9 microg/kg (12.9-31.1 microg/kg), respectively.

CONCLUSIONS

Using the modified Dixon's up-and-down method, the bolus dose of alfentanil for successful tracheal intubation was 10.7+/-2.1 microg/kg in 50% of adult patients during inhalation induction using 5% sevoflurane and 60% nitrous oxide in oxygen without neuromuscular blocking agent in day-case anaesthesia.

Fentanyl dose?response curves when inserting the LMA Classic?laryngeal mask airway

Probit analysis was used to predict an optimal dose of fentanyl, co-administered with propofol 2.5 mg.kg(-1), when inserting the laryngeal mask airway. In all, 21 male and 54 female healthy Chinese patients, aged 18-63 years, requiring anaesthesia for minor surgery were recruited. They were assigned to one of five groups: placebo, 0.5, 1.0, 1.5 and 2.0 microg.kg(-1). Insertion was performed 90 s after administration and insertion conditions assessed using a six-category score. Dose-response curves could only be drawn for swallowing and movement categories, and only the ED(50) could be predicted with certainty. To provide optimal conditions in over 95% of patients, fentanyl doses well above the clinical range were required. A standard fentanyl dose of 1 mug.kg(-1), co-administered with propofol 2.5 mg.kg(-1), provided optimal conditions in 65% of cases. Ninety seconds may have been insufficient time for fentanyl to reach its peak effect.

Comparison of Propofol and Sevoflurane for Laryngeal Mask Airway Insertion in Elderly Patients

BACKGROUND

Sevoflurane and propofol have been widely used for anesthesia induction. This study compared the efficacies of sevoflurane and propofol inductions for laryngeal mask airway (LMA) insertion in elderly patients.

METHODS

Ninety patients, aged 60 or more, received anesthesia induction with propofol and with sevoflurane 8% using the vital capacity breath (VCB) or tidal volume breath (TVB) techniques. Hemodynamic changes, induction time, complications, and the quality and ease of LMA insertion were observed.

RESULTS

LMA was inserted most, less or least rapidly with propofol (89 +/- 28 s), sevoflurane 8% using the VCB (163 +/- 34 s) or TVB (205 +/- 44 s) techniques, respectively. Anesthesia induction with propofol or sevoflurane 8% using the VCB technique produced either more frequent apnea or greater reduction in mean blood pressure than with sevoflurane 8% using the TVB technique.

CONCLUSIONS

Sevoflurane 8% using the TVB technique provides a smoother induction with a stable hemodynamic profile, less apnea and technical demand, but requiring longer time for LMA insertion in unpremedicated elderly patients.

Efficacy of the A-line AEP monitor as a tool for predicting successful insertion of a laryngeal mask during sevoflurane anesthesia

BACKGROUND

The use of clinical signs for assessing depth of anesthesia is unreliable during periods with little noxious stimulation. A patient may appear adequately anesthetized at one moment at a given level of stimulation, but may later, when facing other more intense stimuli, show signs of insufficient anesthesia. In order to prevent under- or overdosing of anesthetics, an anesthesia depth monitor that is able to predict responses to noxious stimulation would therefore be useful. Auditory evoked potentials (AEP) is one of several physiological parameters under investigation. The method has been improved by rapid extraction and conversion of the AEP curve into an index (A-Line ARX Index = AAI). We aimed to determine the clinically required depth of anesthesia, measured by the A-line AEP Monitor, for at least 90% probability of acceptable insertion conditions for a laryngeal mask airway (LMA).

METHODS

We studied 112 patients anesthetized by mask with increasing concentration of sevoflurane in oxygen. The monitor was programmed to give an alarm at AAI between 15 and 40 according to randomization. When the alarm sounded, the end-expiratory sevoflurane concentration was recorded and the LMA inserted. Insertion conditions were assessed by an observer blinded to the AAI.

RESULTS

The ED(95) and prediction probability (P(K)) for AAI were 14.5 (CI 7.4-21.6) and 0.76 (0.66-0.86), respectively, while the ED(95) and P(K) for expiratory sevoflurane concentration were 4.36% (CI 3.73-4.98) and 0.95 (0.91-0.99).

CONCLUSIONS

AAI indicates the level of depth of anesthesia necessary for acceptable laryngeal mask insertion conditions. End-expiratory sevoflurane concentration was the better predictor.

Co-administration of alfentanil-propofol improves laryngeal mask airway insertion compared to fentanyl-propofol

PURPOSE

Insertion of the laryngeal mask airway (LMA) requires sufficient depth of anesthesia to relax the jaw and obtund airway reflexes. Recent studies suggest that the short-acting opioid alfentanil provides the best insertion conditions. We therefore compared the insertion conditions following co-administration of alfentanil-propofol with more commonly used fentanyl-propofol.

METHODS

One hundred forty ASA I or II patients, age 18-81 yr, requiring minor surgery were recruited. They were randomized to receive either alfentanil (10 microg x kg(-1); n = 73) or fentanyl (1 microg x kg(-1); n = 67) with propofol (2.5 mg x kg(-1)) 90 sec prior to LMA (size 3 or 4) insertion. A six variable (mouth opening, ease of insertion, swallowing, coughing, movement and laryngospasm) three-point (nil / partial / total) score was used to assess insertion conditions. Duration of post-insertion apnea was recorded. Insertion conditions were compared using Chi-square for trends.

RESULTS

The two groups were demographically similar. Mouth opening and ease of insertion were not improved with alfentanil co-administration. Alfentanil-propofol reduced the incidence of swallowing, gagging, movement and laryngospasm (P < 0.05), with 29% (alfentanil) compared to 45% (fentanyl) of patients responding (P = 0.05) to LMA insertion. Apnea [mean (SD)] following alfentanil lasted 154 (139) sec compared to 82 (61) sec following fentanyl (P = 0.001).

CONCLUSION

Co-administration of alfentanil-propofol provided better insertion conditions than fentanyl-propofol, though apnea was prolonged by 72 sec.

Facilitation of laryngeal mask airway insertion: effects of remifentanil administered before induction with target-controlled propofol infusion

Eighty-six adult day-case patients were recruited into a prospective, randomised study and allocated to one of two groups. Patients received either intravenous remifentanil 0.3 microg.kg(-1) or an equivalent volume of sodium chloride 0.9% followed by induction of anaesthesia with propofol target-controlled infusion until the effect (brain) site calculated concentration was 2 microg.ml(-1). Jaw opening and ease of laryngeal mask insertion were assessed immediately after mask insertion. A higher incidence of failure of induction of anaesthesia was observed in the control group compared with the remifentanil group [15 (35%) vs. 3 (7%); p < 0.01] and addition of remifentanil significantly increased the ease and success of laryngeal mask insertion, with grade 1 (no coughing/gagging) conditions observed in 29 (68%) of the remifentanil group and 21 (49%) of the control group (p < 0.01). The doses of remifentanil and propofol used were not associated with any significant cardiorespiratory instability. In conclusion, when combined with propofol target-controlled infusion, remifentanil 0.3 microg.kg(-1) facilitates laryngeal mask insertion with minimal adverse haemodynamic changes.

Tracheal intubation without muscle relaxant--a technique using sevoflurane vital capacity induction and alfentanil

This randomized controlled study examined intubating conditions and haemodynamic changes following sevoflurane nitrous oxide induction in four groups: three different doses of alfentanil compared with low-dose alfentanil and suxamethonium. All patients received atropine 0.3 mg i.v. before induction of anaesthesia with vital capacity breaths of sevoflurane 8% (more than 7% in the inspiratory gas) in 60% nitrous oxide and oxygen. Patients were allocated randomly to four groups of intravenous supplements: group SA20, alfentanil 20 microg x kg(-1); group SA25, alfentanil 25 microg x kg(-1); group SA30, alfentanil 30 microg x kg(-1); group SSA, alfentanil 10 microg x kg(-1) and suxamethonium 1 mg x kg(-1). Orotracheal intubation and assessment of intubating conditions was performed by one of the investigators who was blinded to the subject's group. Intubating conditions were satisfactory or excellent in 83%, 80%, 92% and 96% of patients in groups SA20, SA25, SA30 and SSA respectively. These differences were not statistically significant. The increase in heart rate associated with laryngoscopy and tracheal intubation was effectively attenuated in all groups. Mean arterial pressure decreased significantly and similarly after induction in all groups. Two minutes after intubation the mean arterial pressure was increased significantly (P<0.05) compared to the post-induction value in group SSA. The intubating conditions obtained with sevoflurane plus alfentanil 30 microg x kg(-1) were comparable to those provided by the sevoflurane, suxamethonium and alfentanil 10 microg x kg(-1) combination.