Comparison of the anaesthetic requirement with target-controlled infusion of propofol to insert the laryngeal tube vs. the laryngeal mask

Male requires a higher median target effect-site concentration of propofol for I-gel placement when combined with dexmedetomidine

OBJECTIVE

The supraglottic airway device (SAD) can be used for airway management of spontaneous breathing patients, and propofol is commonly applied for the SAD placement. This study was designed to assess the effect of gender on median target effect-site concentration (Ce₅₀) of propofol for I-gel placement when combined with dexmedetomidine.

MATERIAL AND METHOD

19 males and 18 females, aged 18 to 59 and undergoing elective surgery, were enrolled. After intravenous infusion of dexmedetomidine 1.0μg/kg over 10min followed by continuous infusion of 0.4μg/kg/h, target-controlled infusion of propofol under Marsh model was started and the initial Ce of propofol was set at 4.79μg/mL and 4.35μg/mL in the male and female patients, respectively. The I-gel was inserted when the Ce of propofol reached the pre-set concentration and bispectral index value was less than 60. The Ce of propofol required for I-gel placement was determined by the Dixon up-and-down method.

RESULTS

The Ce₅₀ (95% confidence interval) of propofol required for I-gel placement were 4.082μg/mL (3.798-4.332μg/mL) and 3.509μg/mL (3.266-3.749μg/mL) in male and female patients, respectively, with a significantly higher Ce₅₀ in males.

CONCLUSION

When combined with dexmedetomidine, males require a higher Ce₅₀ of propofol for I-gel placement compared to females.

Evaluation of optimum time for intravenous cannulation after sevoflurane induction of anesthesia in different pediatric age groups

Background and Aims

The ideal time for intravenous (IV) cannulation following inhalational induction in children is debatable. The effect of age on this time has not been studied. We evaluated the optimum time for IV cannulation after sevoflurane induction of anesthesia in different pediatric age groups.

Material and Methods

A prospective interventional study based on Dixon's sequential up and down method was conducted in children of age 1-10 years. They were grouped according to their age - Group 1: 1-3 years, Group 2: >3-7 years, and Group 3: >7-10 years. Anesthesia was induced with 8% sevoflurane in 5 L of 100% oxygen. IV cannulation was attempted at 3.5 min in the first child in each group. The time for cannulation in the next child was stepped up or down by 30 s depending on positive or negative response, respectively, in the previous child. Children were recruited till a minimum of six pairs of failure-success sequence which was obtained in each group. The mean of midpoints of the failure-success sequence was calculated to obtain the time for cannulation in 50% of the children in each group.

Results

Total number of children in Groups 1, 2, and 3 were 24, 23, and 24, respectively. The mean (95% confidence level) time for IV cannulation after sevoflurane induction in Groups 1, 2, and 3 was 53.6 (40.0-67.1), 105 (62.6-147.4), and 143.6 (108.8-178.4) s, respectively. This time was significantly shorter in Group 1 compared to those in Groups 2 and 3.

Conclusion

The optimum time for IV cannulation in 50% of the children after sevoflurane induction of anesthesia was shorter in children of age 1-3 years than in older children.

Male patients require higher optimal effect-site concentrations of propofol during i-gel insertion with dexmedetomidine 0.5 μg/kg

BACKGROUND

The pharmacokinetics and pharmacodynamics of an anesthetic drug may be influenced by gender. The purpose of this study was to compare effect-site half maximal effective concentrations (EC50) of propofol in male and female patients during i-gel insertion with dexmedetomidine 0.5 μg/kg without muscle relaxants.

METHODS

Forty patients, aged 20-46 years of ASA physical status I or II, were allocated to one of two groups by gender (20 patients per group). After the infusion of dexmedetomidine 0.5 μg/kg over 2 min, anesthesia was induced with a pre-determined effect-site concentration of propofol by target controlled infusion. Effect-site EC50 values of propofol for successful i-gel insertion were determined using the modified Dixon's up-and-down method.

RESULTS

Mean effect-site EC50 ± SD of propofol for successful i-gel insertion was significantly higher for men than women (5.46 ± 0.26 μg/ml vs. 3.82 ± 0.34 μg/ml, p < 0.01). The EC50 of propofol in men was approximately 40% higher than in women. Using isotonic regression with a bootstrapping approach, the estimated EC50 (95% confidence interval) of propofol was also higher in men [5.32 (4.45-6.20) μg/ml vs. 3.75 (3.05-4.43) μg/ml]. The estimated EC95 (95% confidence interval) of propofol in men and women were 5.93 (4.72-6.88) μg/ml and 4.52 (3.02-5.70) μg/ml, respectively.

CONCLUSIONS

During i-gel insertion with dexmedetomidine 0.5 μg/kg without muscle relaxant, male patients had higher effect-site EC50 for propofol using Schnider's model. Based on the results of this study, patient gender should be considered when determining the optimal dose of propofol during supraglottic airway insertion.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT02268656. Registered August 26, 2014.

Effect-site concentration of propofol required for LMA-Supreme™ insertion with and without remifentanil: a randomized controlled trial

BACKGROUND

A new supraglottic device, the LMA-Supreme™, has recently become available for clinical use. Information on anaesthetic and co-adjuvant requirements for insertion of the LMA-Supreme™ is limited. The present study aimed to evaluate the optimal effect-site concentration of propofol in 50 % (EC50) of adults necessary for successful insertion of the LMA-Supreme™ and to examine remifentanil's effect on propofol requirements.

METHODS

Fifty-eight elective patients (aged 18-60 years; ASA (American Society Anaesthesiologists) physical status classification I and II) scheduled for day surgery were randomly assigned to one of two groups: propofol with saline or propofol with remifentanil. Anaesthesia was induced by target-controlled infusion according to predetermined effect-site concentrations of propofol and remifentanil (5 ng.mL(-1)). The EC50 was calculated using Dixon's up-and-down method. Ten minutes following drug administration, LMA-Supreme™ insertion was attempted without the use of muscle relaxant drugs.

RESULTS

In the propofol + saline group, the EC50 of propofol required for LMA-Supreme™ insertion was 6.32 ± 0.67 μg.mL(-1) (95 % CI, 5.69-6.94 μg.mL(-1)). With the addition of remifentanil at an effect-site concentration of 5 ng.mL(-1), the EC50 of propofol required for LMA-Supreme™ insertion was 2.50 ± 0.80 μg.mL(-1) (95 % CI, 1.82-3.17 μg.mL(-1); p < 0.0001).

CONCLUSIONS

The propofol requirement for smooth insertion of the LMA-Supreme™ was 60 % less when remifentanil (5 ng.mL(-1)) was co-administered.

CLINICAL TRIAL REGISTRATION

Identified as NCT01974648 at www.clinicaltrials.gov .

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.

A randomized controlled trial of the effect of preoperative dexmedetomidine on the half maximal effective concentration of propofol for successful i-gel insertion without muscle relaxants

BACKGROUND

Dexmedetomidine is a useful anesthetic adjuvant for general anesthesia. We determined whether preoperative dexmedetomidine administration could reduce the half maximal effective concentration (EC50) of propofol for successful i-gel insertion without muscle relaxants.

METHODS

Thirty-seven patients were randomly allocated to one of two groups. In the dexmedetomidine group (n = 19), dexmedetomidine (1 µg/kg) was loaded for 10 min preoperatively. In the control group (n = 20), the same volume of 0.9% normal saline was administered in the same manner. The EC50 of propofol for successful i-gel insertion was determined using Dixon's up-and-down method. The EC50 of propofol was calculated as the midpoint concentration after at least six crossover points had been obtained. For successful i-gel insertion, all of the following four factors were required—(1) no major movement of the body within 1 min of insertion, (2) no significant resistance to mouth opening, (3) cough ≤2, and (4) visible square wave capnogram without air leakage at a peak airway pressure of <10 cmH2O. Mean blood pressure (MBP) and heart rate (HR) were monitored during the peri-insertion period of i-gel.

RESULTS

The EC50 of propofol for successful i-gel insertion was 3.18 μg/mL in the dexmedetomidine group and 6.75 μg/mL in the control group (p < 0.001). The incidence of hypotension (MBP <80% of the baseline) during the peri-insertion period of i-gel was higher in the control group (p = 0.001), whereas the incidence of bradycardia (HR <80% of the baseline) was higher in the dexmedetomidine group (p = 0.001).

CONCLUSIONS

Preoperative dexmedetomidine reduced the EC50 of propofol for successful i-gel insertion without muscle relaxants.

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.

Determination of optimum time for intravenous cannulation after induction with sevoflurane and nitrous oxide in children premedicated with midazolam

BACKGROUND

It has been shown that early placement of an intravenous line in children administered sevoflurane anesthesia increased the incidence of laryngospasm and movement. However, the optimal time for safe cannulation after the loss of the eyelash reflex during the administration of sevoflurane and nitrous oxide is not known.

AIM

The aim of the study was to determine the optimum time for intravenous cannulation after the induction of anesthesia with sevoflurane and nitrous oxide in children premedicated with oral midazolam.

METHOD

We performed a prospective, observer-blinded, up-down sequential, allocation study, and children, aged 2-6 years, ASA physical status I, scheduled for an elective procedure undergoing inhalational induction were included in the study. Anesthesia was induced with sevoflurane and nitrous oxide after premedication with oral midazolam. For the first child, 4 min after the loss of the eyelash reflex, the intravenous cannulation was attempted by an experienced anesthesiologist. The time for intravenous cannulation was considered adequate if movement, coughing, or laryngospasm did not occur. The time for cannulation was increased by 15 s if the time was inadequate in the previous patient, and conversely, the time for cannulation was decreased by 15 s if the time was adequate in the previous patient. The probit test was used in the analysis of up-down sequences.

RESULTS

A total of 32 children were enrolled sequentially during the study period. The adequate time for effective intravenous cannulation after induction with sevoflurane and nitrous oxide in 50% and 95% of patients were 1.29 min (95% confidence interval, 0.96-1.54 min) and 1.86 min (95% confidence interval 1.58-4.35 min), respectively.

CONCLUSION

We recommend waiting 2 min for attempting intravenous placement following the loss of the eyelash reflex in children sedated with midazolam and receiving an inhalation induction with sevoflurane and nitrous oxide.

Randomized comparison of the i-gel™, the LMA Supreme™, and the Laryngeal Tube Suction-D using clinical and fibreoptic assessments in elective patients

BACKGROUND

The i-gel™, LMA-Supreme (LMA-S) and Laryngeal Tube Suction-D (LTS-D) are single-use supraglottic airway devices with an inbuilt drainage channel. We compared them with regard to their position in situ as well as to clinical performance data during elective surgery.

METHODS

Prospective, randomized, comparative study of three groups of 40 elective surgical patients each. Speed of insertion and success rates, leak pressures (LP) at different cuff pressures, dynamic airway compliance, and signs of postoperative airway morbidity were recorded. Fibreoptic evaluation was used to determine the devices' position in situ.

RESULTS

Leak pressures were similar (i-gel™ 25.9, LMA-S 27.1, LTS-D 24.0 cmH2O; the latter two at 60 cmH2O cuff pressure) as were insertion times (i-gel™ 10, LMA-S 11, LTS-D 14 sec). LP of the LMA-S was higher than that of the LTS-D at lower cuff pressures (p <0.05). Insertion success rates differed significantly: i-gel™ 95%, LMA-S 95%, LTS-D 70% (p <0.05). The fibreoptically assessed position was more frequently suboptimal with the LTS-D but this was not associated with impaired ventilation. Dynamic airway compliance was highest with the i-gel™ and lowest with the LTS-D (p <0.05). Airway morbidity was more pronounced with the LTS-D (p <0.01).

CONCLUSION

All devices were suitable for ventilating the patients' lungs during elective surgery.

TRIAL REGISTRATION

German Clinical Trial Register DRKS00000760.

An optimum time for intravenous cannulation after induction with sevoflurane in children

BACKGROUND

It is a common practice to perform inhalational induction with sevoflurane followed by intravenous cannulation in children. However, there is little information regarding the time at which the intravenous cannulation can be attempted safely after sevoflurane induction.

AIM

To determine the optimal time for safe intravenous cannulation in children induced with sevoflurane.

METHODS

Pediatric patients aged 4-10 years receiving sevoflurane inhalational induction for elective cases were recruited. General anesthesia was induced with sevoflurane and oxygen via mask, then intravenous cannulation was attempted. The time for intravenous cannulation was determined by the use of up-and-down method using 30 s as a step size. Intravenous cannulation without any movement, coughing, or laryngospasm was considered successful. The up-and-down sequences were analyzed by the probit test.

RESULTS

The time for effective intravenous cannulation in 50% patients was 1.90 min (95% confidence limits, 1.24-2.41 min). The time for effective cannulation in 95% of patient population was 3.32 min (95% confidence limits, 2.68-6.77 min).

CONCLUSION

We recommend an optimal time of 3.5 min for attempting intravenous cannulation after the loss of eyelash reflex with sevoflurane induction.

Comparison of the effect-site concentrations of remifentanil for Streamlined Liner of the Pharynx Airway (SLIPA) versus laryngeal mask airway SoftSealTM insertion during target-controlled infusion of propofol

This study was designed to determine the optimal dose of remifentanil required for the successful insertion of Streamlined Liner of the Pharynx Airway (SLIPA) and to compare it to that required for laryngeal mask airway (LMA) insertion in patients receiving a propofol infusion at a standard effect-site concentration. Fifty-eight patients scheduled to undergo general anaesthesia were randomly assigned to either the SLIPA (n = 29) or LMA (n = 29) group. All patients were premedicated with midazolam 0.05 mg x kg(-1) and glycopyrrolate 0.004 mg x kg(-1) intramuscularly. After the administration of lignocaine 1 mg x kg(-1) intravenously, a propofol infusion was started at an effect-site concentration of 3.5 microg x ml(-1) with a remifentanil infusion without a neuromuscular blocking agent. The remifentanil dose was determined by the modified up-and-down method starting in each group at 4 ng x ml(-1). Six minutes after induction, the airway device was inserted. Airway device insertion was classified as 'success' or 'failure' based on patient response. From the isotonic regression analysis and bootstrap distribution, the EC50 of remifentanil for SLIPA and LMA were 0.93 ng x ml(-1) (95% confidence interval [CI] 0.81 to 1.50 ng x ml(-1) and 1.36 ng x ml(-1) (95% CI 1.19 to 2.06 ng x ml(-1)) respectively, and the EC95 for SLIPA and LMA insertions were 1.90 ng x ml(-1) (95% CI 1.39 to 1.95) and 2.43 ng x ml(-1) (95% CI 1.80 to 2.46 ng x ml(-1)) respectively. Using the 83% CIs from the bootstrap distribution, EC50 for SLIPA was significantly less than that of LMA (0.83 to 1.23 vs 1.26 to 2.00, respectively) (P < 0.05). These findings suggest that the insertion of SLIPA needs about a 32% lower depth of anaesthesia than LMA insertion.

Effect-site concentration of remifentanil for laryngeal mask airway insertion during target-controlled infusion of propofol

The purpose of this study was to determine the effect-site concentration of remifentanil that would provide optimal conditions for successful laryngeal mask airway insertion during a target-controlled infusion (TCI) of propofol at 3.5 microg.ml(-1) without the use of neuromuscular blockade. Five minutes after propofol infusion, remifentanil was infused at a dose determined by a modified Dixon's up-and-down method. Five minutes after remifentanil infusion, the laryngeal mask was inserted. The effect-site concentration of remifentanil for successful laryngeal mask insertion in 50% of adults (EC(50)) was 3.04 (SD 0.49) ng.ml(-1) during a TCI of 3.5 microg.ml(-1) propofol without neuromuscular blockade. From the probit analysis, the EC(50) and EC(95) of remifentanil were 2.84 ng.ml(-1) (95% CI 2.09-3.57 ng.ml(-1)) and 3.79 ng.ml(-1) (95% CI 3.26-9.25 ng.ml(-1)), respectively.

A comparison of the end-tidal sevoflurane concentration for removal of the laryngeal mask airway and laryngeal tube in anesthetized children

BACKGROUND

In this study we quantified and compared the optimal sevoflurane concentration required to prevent coughing or moving during or after removal of the laryngeal mask airway (LMA) and the laryngeal tube (LT) in anesthetized children.

METHODS

Forty unpremedicated children, aged 8 mo to 12 yr, were randomly allocated to receive the LMA or LT. General anesthesia was induced via mask with sevoflurane and the LMA or LT was inserted. Anesthesia was maintained with sevoflurane and oxygen. At the end of surgery, a predetermined end-tidal sevoflurane concentration was maintained for at least 10 min and the LMA or LT was removed. Using Dixon's up-down method, the concentration for LMA and LT removal was determined by adjusting the dose by a 0.2% increment. Success was defined by the absence of coughing, teeth clenching, gross purposeful movement, breath holding, laryngospasm, and desaturation.

RESULTS

The end-tidal concentration of sevoflurane to achieve successful LMA removal in 50% of children was 1.90%, in 95% of children was 2.15%. For the LT, the concentrations were 1.83% and 2.00%. The 50% effective dose values did not differ significantly between groups.

CONCLUSIONS

LMA and LT removal in 95% of anesthetized children (aged 8 mo to 12 yr) can be safely accomplished without coughing, moving, or any other airway complications at 0.86 and 0.80 minimum alveolar anesthetic concentration, respectively, and a similar concentration should be used for removal of the LT or LMA in children.

Remifentanil halves the EC50 of propofol for successful insertion of the laryngeal mask airway and laryngeal tube in pediatric patients

BACKGROUND

Propofol and remifentanil are the drugs of choice for insertion of the supraglottic airway without muscle relaxants for short duration surgery. In this study, we compared propofol concentrations required for insertion of laryngeal mask way (LMA) or laryngeal tube (LT) with and without remifentanil.

METHODS

We included children scheduled for surgeries lasting <2 h, and assigned them to four groups in a randomized, double-blind manner: LMA with propofol + saline (LMA-P), LT with propofol + saline (LT-P), LMA with propofol + 7.5 ng/mL remifentanil (LMA-PR), LT with propofol +7.5 ng/mL remifentanil (LT-PR). Anesthesia was conducted by target-controlled infusion in determined target effect site concentration of propofol and remifentanil with the STELPUMP program. The EC50 of propofol for airway device placement was determined using Dixon's up-and-down method. The concentration of propofol for consecutive patients in each group was determined by the response of the previous patient, using increments or decrements of 0.2 microg/mL.

RESULTS

In patients receiving remifentanil, propofol EC50 for insertion of a LMA was 2.57 +/- 0.22 microg/mL and that of LT was 2.59 +/- 0.20 microg/mL (n.s.). In patients receiving saline, the corresponding values were 5.45 +/- 0.21 microg/mL and 5.58 +/- 0.23 microg/mL (n.s.). Conditions were excellent in 64% (9 of 14) and 79% (11 of 14) of patients receiving remifentanil, but in patients receiving saline, the values were 18% (2 of 11) for the LMA and 40.0% (4 of 10) for the LT.

CONCLUSIONS

Remifentanil 7.5 ng/mL reduced the propofol concentration required for airway insertion by half, and improved conditions for insertion. Propofol concentrations for insertion of the LMA and LT were similar.

Minimum alveolar concentration of sevoflurane for laryngeal mask airway removal in anesthetized children

BACKGROUND

In children, it is preferable to remove the laryngeal mask airway (LMA) when the patient is still anesthetized. We sought to determine the optimal minimum alveolar concentration of sevoflurane that would allow removal of the LMA in children without airway complications.

METHODS

We studied 25 unpremedicated children between 7 mo and 10 yr of age, ASA Status I, undergoing urologic or plastic surgery. General anesthesia was induced with sevoflurane and oxygen given via mask. The LMA was inserted and anesthesia was maintained with sevoflurane in oxygen. The LMA was removed at the end of surgery when the end-tidal sevoflurane concentration had reduced to a predetermined level, determined by the up-and-down method, with 0.2% as a step size. A removal accomplished without coughing, teeth clenching, gross purposeful movement, breath holding or laryngospasm, during or within 1 min after removal, was considered to be successful.

RESULTS

The minimum alveolar concentration of sevoflurane at which 50% of LMA removals were successful was 1.84% (95% confidence limits, 1.45%-1.96%), and the 95% effective dose for successful removal was 2.17% (95% confidence limits, 2.02%-3.48%).

CONCLUSIONS

LMA removal may be accomplished without coughing, moving, or any other airway complication at 1.84% end-tidal sevoflurane concentration in 50% of anesthetized children.