A comparison of the insertion characteristics of the laryngeal tube and the laryngeal mask airway: a study of the ED50 propofol requirements

Predicted effect-site concentrations of remimazolam for i-gel insertion: a prospective randomized controlled study

This study is the first to report 50% and 95% effect-site concentrations (EC50 and EC95, respectively) of the new short-acting benzodiazepine, remimazolam, for the successful insertion of i-gels with co-administration of fentanyl. Thirty patients (38 ± 5 years old, male/female = 4/26) were randomly assigned into five groups to receive one of five different remimazolam doses (0.1, 0.15, 0.2, 0.25, and 0.3 mg/kg bolus followed by infusion of 1, 1.5, 2, 2.5, and 3 mg/kg/h, respectively, for 10 min), which were designed to maintain a constant effect-site concentration of remimazolam at the time of i-gel insertion. At 6 min after the start of remimazolam infusion, all patients received 2 µg/kg fentanyl. i-gel insertion was attempted at 10 min and the success or failure of insertion were assessed by the patient response. Probit analysis was used to estimate the EC50 and EC95 values of remimazolam with 95% confidence intervals (CIs). In the five remimazolam dose groups, two, two, four, five, and six of the six patients in each group had an i-gel successfully inserted. Two patients in the lowest remimazolam dose group were conscious at the time of i-gel insertion and were counted as failures. The EC50 and EC95 values of remimazolam were 0.88 (95% CI, 0.65-1.11) and 1.57 (95% CI, 1.09-2.05) µg/ml, respectively. An effect-site concentration of ≥ 1.57 µg/ml was needed to insert an i-gel using remimazolam anesthesia, even with 2 µg/kg fentanyl. Trial registration: The study was registered in Japan Registry of Clinical Trials on 19 April 2021, Code jRCTs041210009.

High daily caffeine intake is associated with lower propofol requirements for anesthetic induction

Background and Aims

There is significant interindividual variation in the dose of propofol required for anesthetic induction. Factors dictating this are poorly described, but understanding them would be useful for anesthetic drug dosing. It has been shown in rats and recently in humans that caffeine administration accelerates recovery from anesthesia, but no study has assessed the effect on anesthetic induction.

Material and Methods

Forty American Society of Anesthesiologists (ASA)-I, 18-65-year-old patients, undergoing day case general anesthesia with propofol and fentanyl took part in this observational study. Total daily caffeine intake (mg) was estimated using the caffeine assessment tool and caffeine content values from the US Department of Agriculture National Nutrient Database. Pharmacokinetic-pharmacodynamic modeling was used to estimate the effect site concentration of propofol at loss of consciousness (Ce(p) LOC).

Results

Median (interquartile range [IQR]) daily caffeine intake was 106 (51-193) mg. Ce(p) LOC was lower in those with caffeine intake greater than or equal to the median of 106 mg (median (IQR) = 0.64 μg/ml (0.51-0.72) vs. 0.70 μg/ml (0.57-1.10), P = 0.04). The effect was robust when controlling for weight-adjusted fentanyl dose, age, smoking status, and alcohol intake (F (1,34) = 4.66, P = 0.04).

Conclusion

High daily caffeine intake is associated with lower propofol requirements for day case anesthetic induction. We propose that high daily caffeine intake may cause lower arousal levels prior to surgery due to a relative caffeine deficit caused by being nil by mouth. As such, assessment of daily caffeine intake preoperatively may aid anesthetic drug dosing.

Remifentanil requirement for i-gel insertion is reduced in male patients with Parkinson's disease undergoing deep brain stimulator implantation: an up-and-down sequential allocation trial

Background

Laryngeal mask airways have been widely used in clinical practice. The aim of this study was to investigate whether the remifentanil requirement for facilitation of i-gel insertion in Parkinson’s disease (PD) patients undergoing deep brain stimulation (DBS) surgery was different from that in non-PD (NPD) patients undergoing intracranial surgery.

Study design

An up-and-down sequential allocation trial.

Methods

Male patients aged between 40 and 64 years old were enrolled. The first patient in each group (PD and NPD) group received an effect-site concentration (Ce) of remifentanil (Minto pharmacokinetic model) of 4.0 ng.ml⁻¹ during a target-controlled infusion (TCI) of 3.5 μg.ml⁻¹ propofol (Marsh pharmacokinetic model). The next dose of remifentanil was determined by the response of the previous patient. The Ce of remifentanil required for i-gel insertion in 50% of patients (EC₅₀) was estimated by the modified Dixon’s up-and-down method and by probit analysis.

Results

The PD group included 24 patients and the NPD group included 23. The EC₅₀ of remifentanil for i-gel insertion during a TCI of 3.5 μg.ml⁻¹ propofol estimated by the modified Dixon’s up-and-down method in PD patients (2.38 ± 0.65 ng.ml⁻¹) was significantly lower than in NPD patients (3.21 ± 0.49 ng.ml⁻¹) (P = 0.03). From the probit analysis, the EC₅₀ and EC₉₅ (effective Ce in 95% of patients) of remifentanil were 1.95 (95% CI 1.52–2.36) ng.ml⁻¹ and 3.12 (95% CI 2.53–5.84) ng.ml⁻¹ in PD patients and 2.85 (95% CI 2.26–3.41) ng.ml⁻¹ and 4.57 (95% CI 3.72–8.54) ng.ml⁻¹ in NPD patients, respectively.

Conclusions

The remifentanil requirement for successful i-gel insertion is reduced in male PD patients undergoing DBS implantation during propofol TCI induction. Clinicians should closely monitor the remifentanil requirement in patients with PD.

Trial registration

Registered at http://www.chictr.org.cn (ChiCTR1900021760).

[Comparison of ED50 of intranasal dexmedetomidine sedation in children with acyanotic congenital heart disease before and after cardiac surgery]

OBJECTIVE

To compare the median effective dose (ED50) of intranasal dexmedetomidine for procedural sedation in uncooperative pediatric patients with acyanotic congenital heart disease before and after cardiac surgery.

METHODS

We prospectively recruited 47 children (22 in preoperative group and 25 in postoperative group) who needed sedation for transthoracic echocardiography (TTE). A modified up-and-down sequential study design was employed to determine dexmedetomidine dose for each patient with a starting dose of 2 μg/kg in both groups; dexmedetomidine doses for subsequent subjects were determined according to the responses from the previous subject using the up-and-down method at a 0.25 μg/kg interval. The ED95 was determined using probit regression. The onset time, examination time, wake-up time and adverse effects were measured, and the safety was evaluated in terms of changes in vital signs every 5 min.

RESULTS

The ED50 value of intranasal dexmedetomidine for sedation was 1.84 μg/kg (95% CI: 1.68-2.00 μg/kg) in children with congenital heart disease before cardiac surgery, and 3.38 μg/kg (95% CI: 3.21-3.54 μg/kg) after the surgery. No significant difference was found between the two groups in the demographic variables, onset time, examination time, wake-up time, or adverse effects.

CONCLUSIONS

In children with acyanotic congenital heart disease, the ED50 of intranasal dexmedetomidine for TTE sedation increases to 3.38 μg/ kg after cardiac surgery from the preoperative value of 1.84 μg/kg.

Inhibitory concentration of propofol in combination with dexmedetomidine during microelectrode recording for deep brain stimulator insertion surgeries under general anesthesia

BACKGROUND

Microelectrode recording (MER) for target refinement is widely used in deep brain stimulator insertion for Parkinson disease. Signals may be influenced by anesthetics when patients receive general anesthesia (GA). This study determined the inhibitory concentration (IC) of propofol on MER signals when it was coadministered with dexmedetomidine.

METHODS

Patients were anesthetized with dexmedetomidine (0.5 μg·kg loading, followed by infusion at 0.4 μg·kgh) and propofol through target-controlled infusion for GA with tracheal intubation. The surgeon conducted the online scoring of the background signals, spiking frequency, amplitude, and pattern of single-unit activities by using a 0-10 verbal numerical rating scale (NRS; 0, maximal suppression; 10, minimal suppression), and responses were grouped into suppression (NRS ≤ 6) and nonsuppression (NRS > 6). The median inhibitory concentration (IC50) of propofol (as target effect-site concentrations: Ceprop) was determined using modified Dixon's up-and-down method. Probit regression analysis was further used to obtain the dose-response relationship, and IC05 and IC95 were calculated.

RESULTS

Twenty-three adult patients participated in this study. Under the concomitant infusion of dexmedetomidine, the predicted IC50 value (95% CI) of Ceprop for neuronal suppression during MER was 1.29 (1.24-1.34) μg·mL as calculated using modified Dixon's up-and-down method. Using probit analysis, the estimated IC05, IC50, and IC95 values (95% CIs) were 1.17 (0.87-1.23), 1.28 (1.21-1.34), and 1.40 (1.33-1.85) μg·mL, respectively.

CONCLUSION

Our data provided reference values of propofol for dosage adjustment to avoid interference on MER under GA when anesthetics have to be continuously infused during recording.

Median effective dose of intranasal dexmedetomidine sedation for transthoracic echocardiography examination in postcardiac surgery and normal children: An up-and-down sequential allocation trial

BACKGROUND

Dexmedetomidine (DEX) has been used for sedation in young infants and children undergoing transthoracic echocardiography (TTE). The median effective dose of intranasal DEX has not been described for postcardiac surgery children. Postcardiac surgery children could require more DEX to achieve satisfactory sedation for TTE examination than children suspected of congenital heart disease.

OBJECTIVES

To study whether postcardiac surgery children need a larger dose of DEX for TTE than normal children.

DESIGN

A double-blind sequential allocation trial with doses determined by the Dixon and Massey up-and-down method.

SETTING

A tertiary care teaching hospital from 25 October to 30 November 2016.

PATIENTS

Children under the age of 3 years requiring intranasal DEX for TTE.

INTERVENTIONS

Children were allocated to a postcardiac surgery group (n = 20) or a normal group (n = 19). The first patient in both groups received intranasal DEX (2 μg kg): using the up-and-down method of Dixon and Massey, the next dose was dependent on the previous patient's response.

MAIN OUTCOME MEASURES

Median effective dose was estimated from the up-and-down method of Dixon and Massey and probit regression. A second objective was to study haemodynamic stability and adverse events with these doses.

RESULTS

The median effective dose (95% confidence interval) of intranasal DEX was higher in postcardiac surgery children than in normal children, 3.3 (2.72 to 3.78) μg kg versus 1.8 (1.71 to 2.04) (μg kg), respectively (P < 0.05). There were no significant differences in time to sedation, time to wake-up or TTE examination time between the two groups for successful sedation. Additionally, there were no significant adverse events.

CONCLUSION

The median effective dose of intranasal DEX for TTE sedation in postcardiac surgery children was higher than in normal children.

TRIAL REGISTRATION

chictr.org.cn identifier: ChiCTR-OOC-16009846.

The optimum sevoflurane concentration for supraglottic airway device Blockbuster™ insertion with spontaneous breathing in obese patients: a prospective observational study

BACKGROUND

Airway management of the obese patient presenting for surgery is more likely to be a challenging problem. Supraglottic airway device has been adopted as a bridge to connect ventilation and tracheal intubation in obese patients who would be suffered with difficult intubation. The optimum sevoflurane concentration for supraglottic airway device insertion allowing spontaneous breathing in 50% of obese patients (ED₅₀) is not known. The purpose of this study was to determine the ED₅₀ of sevoflurane for supraglottic airway device Blockbuster™ insertion with spontaneous breathing in obese patients requiring general anesthesia.

METHODS

Thirty elective obese patients (body mass index 30-50 kg/m²) undergoing bariatric surgery were recruited in this study. The predetermined target sevoflurane concentration (initiating at 2.5% with 0.5% as a step size) was sustained for >5 min using a modified Dixon's up-and-down method, and then the supraglottic airway device Blockbuster™ was inserted. The patient's response to supraglottic airway device insertion was classified as either 'movement' or 'no-movement'. The ED₅₀ of sevoflurane were determined by calculating the midpoint concentration of crossover point from 'movement' or 'no-movement' response.

RESULTS

The ED₅₀ of sevoflurane for supraglottic airway device Blockbuster™ insertion in obese patients calculated using up-and-down method were 2.50 ± 0.60%. The ED₅₀ and ED₉₅ (95% confidence interval) obtained by probit regression analysis were 2.35 (1.28-3.42) % and 4.03 (3.16-17.83) % for supraglottic airway device Blockbuster™ insertion, respectively.

CONCLUSION

We conclude that the optimum end-tidal sevoflurane concentration required for the supraglottic airway device Blockbuster™ insertion allowing spontaneous breathing in 50% of obese patients (ED₅₀) is 2.5 ± 0.6%.

TRIAL REGISTRATION

Chinese Clinical Trial Registry, ChiCTR-IPR-16009071 , Registered on 24 August 2016.

Lack of Sex Difference in Minimum Local Analgesic Concentration of Ropivacaine for Ultrasound-Guided Supraclavicular Brachial Plexus Block

Background

Sex differences, which may be an important variable for determining anesthetic requirements, have not been well investigated in the aspect of local anesthetic. This investigation aimed to compare the minimum local analgesic concentration (MLAC) of ropivacaine for ultrasound-guided supraclavicular brachial plexus block (US-SCB) between men and women.

Material/Method

Patients aged 18–45 years undergoing elective forearm, wrist, or hand surgeries under US-SCB were divided into 2 groups according to sex. The initial concentration was 0.375% ropivacaine 20 mL and the concentration for the next patient was determined by the up-down technique at 0.025% intervals. Success was defined as the absence of any pain in response to a pinprick in the region of all 4 terminal nerves and the skin incision within 45 min. The primary outcome was the MLAC of ropivacaine, which was estimated by the Dixon and Massey method. The analgesia duration, which was defined as the time from the end of the US-SCB injection to the time of feeling discomfort and need for additional analgesics, was observed for each patient.

Results

The MLAC of ropivacaine 20 mL for US-SCB was 0.2675% (95% confidence interval [CI], 0.2512–0.2838%) in men and 0.2675% (95% CI, 0.2524–0.2826%) in women. There was no significant difference in MLAC or the analgesia duration between the 2 groups (P>0.05).

Conclusions

We found no significant sex-related differences in MLAC or analgesia duration of ropivacaine for US-SCB.

Propofol requirement for insertion of I-gel versus laryngeal mask airway: A comparative dose finding study using Dixon's up-and-down method

Background and Aims:

Propofol is the drug of choice when used as sole anesthetic agent for placement of supraglottic airway devices. We aimed to find and compare the propofol dose required for smooth first attempt insertion of I-gel versus the classic laryngeal mask airway (cLMA) using Dixon's up-and-down method.

Material and Methods:

Prospective randomized controlled trial (n-60) was planned. I-gel or cLMA was inserted 60 s after propofol injection whose dose was calculated based on previous patients response as per Dixon's up-and-down method. Propofol requirements for successful placement of devices was noted and compared. Difference between the groups was measured by ANOVA. A P < 0.05 was considered as statistically significant.

Results:

Significantly lower (P < 0.001) propofol dose was required for I-gel (2.02 ± 0.26 mg/kg) insertion than cLMA (2.70 ± 0.28 mg/kg).

Conclusions:

I-gel requires significantly lower dose of propofol for insertion when compared to cLMA.

Comparison of Propofol and Ketamine-Propofol Mixture (Ketofol) on Laryngeal Tube-Suction II Conditions and Hemodynamics: A Randomized, Prospective, Double-Blind Trial

OBJECTIVE

The aim of our study is to compare the effect of ketamine-propofol mixture (ketofol) and propofol on the laryngeal tube-Suction II (LTS II) insertion conditions and hemodynamics.

METHODS

Eighty American Society of Anesthesiologists class 1 and 2 patients were divided into 2 random groups to receive either 1 µg/kg remifentanil and propofol 2 mg/kg in Group P (n = 40), or 1 µg/kg remifentanil and ketofol (using a 1:1 single syringe mixture of 5 mg/mL ketamine and 5 mg/mL propofol) in Group K (n = 40) before induction of anesthesia. After induction, LTS II was inserted. Heart rate and noninvasive blood pressure were recorded before induction of anesthesia (t0); immediately following induction (t1); immediately after LTS II insertion (t2); and 3 minutes (t3), 5 minutes (t4), and 10 (t5) minutes after LTS II insertion. Conditions of insertion of LTS II were assessed and scored 1 to 3 using 6 variables as follows: mouth opening, swallowing, coughing, head and body movements, laryngospasm, and ease of LTS II insertion by the same experienced anesthesiologist who did not know the agents. LTS II insertion summed score was prepared depending upon these variables.

RESULTS

In regard to LTS II insertion summed score, Group K was more favorable than Group P (P < 0.05). Apnea duration was longer in Group P (385.0 seconds [range = 195.0-840.0 seconds]) compared with Group K (325.50 seconds [range = 60.0-840.0 seconds]) but this was not statically significant. The heart rate values were significantly lower at all measurement intervals in both groups compared with the baseline values (P < 0.05). There was no difference in heart rate between Group P and Group K. The mean arterial pressure values were significantly lower at all measurement intervals in Group P compared with baseline values (P < 0.05). In Group K, the mean arterial pressure values were significantly lower at all measurement intervals compared with the baseline values, except t2 (P < 0.05). There was a significant difference between Group P and Group K in terms of mean arterial pressure at t3 (P < 0.05).

CONCLUSIONS

We found that ketofol provided better insertion summed score for LTS II than propofol, with minimal hemodynamic changes.

Propofol EC50 for inducing loss of consciousness is lower in the luteal phase of the menstrual cycle

BACKGROUND

Varying levels of female sex hormones during the menstrual cycle were found to influence the central nervous system. The goal of the present study was to investigate whether the median (50%) effective effect-concentration (EC50) of propofol inducing loss of consciousness (LOC) varies between the luteal and the follicular phases of the menstrual cycle.

METHODS

Twenty-two patients (follicular phase) and 20 patients (luteal phase) undergoing gynaecological procedures under general anaesthesia were enrolled on the study. Anaesthesia was conducted with a target-controlled infusion (TCI) of propofol. The initial target effect-site propofol concentration (Ceprop) was 3.5 µg ml(-1) and was adjusted stepwise by 0.5 µg ml(-1) at 4 min intervals by an up-down sequential method to reach LOC. Anaesthesia was maintained with a propofol TCI guided by the bispectral index. The correlation between female sex hormones and predicted Ceprop at the time of LOC was analysed and emergence time from anaesthesia was recorded.

RESULTS

Propofol EC50 to induce LOC was higher in patients in the follicular phase than those in the luteal phase (4.17 vs 3.58 µg ml(-1), P<0.05). Progesterone correlated significantly with Ceprop at LOC. Emergence time was also longer in the follicular group than in the luteal group (6.5 vs 5.0 min, P<0.05).

CONCLUSIONS

During general anaesthesia, patients in the luteal phase of the menstrual cycle had a lower propofol EC50 for LOC and a shorter emergence time compared with those in the follicular phase. Differences in progesterone levels between menstrual phases may contribute to these anaesthetic effects. Registry number of clinical trial ChiCTR-RCH-12002755.

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.

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.

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.