Cp50 of propofol for laryngeal mask airway insertion using predicted concentrations with and without nitrous oxide

Comparative study of effective-site target controlled infusion with standard bolus induction of propofol for laryngeal mask airway insertion

Several studies demonstrated induction of anesthesia with different plasma target-controlled infusion (TCI) of propofol for LMA insertion. However, there has been no study to compare the standard bolus propofol induction with the effective site TCI for LMA insertion. Objective: Compare the efficacy of induction of anesthesia with propofol for LMA insertion between the effective-site TCI, using 6 μg/mL, and the standard bolus propofol dose of 2.5 mg/kg in elective surgical patients. Methods: A randomized, prospective, single-blinded, clinical study was used for this study. Seventy-eight unpremedicated patients, American Society of Anesthesiologists (ASA) physical status I and II undergoing elective surgical procedure were randomly allocated between two groups. Group 1 received the standard bolus propofol dose of 2.5 mg/kg. Group 2 received effective site TCI (Schnider model) dose of 6 μg/mL for LMA insertion. The hemodynamics and anesthetic depth (Bispectral index score) were monitored and recorded during and immediately after LMA insertion. The number of insertion attempted, insertion quality score, induction time, and propofol doses used were recorded and compared between groups. Results: The success rate of first insertion attempt was equal in both groups (92.3%). There was no significant hemodynamic response difference between the groups during pre-induction, induction, insertion, and post insertion period. The BIS score was significantly lower during post insertion period in group 1 (51.4+11.0) than group 2 (58.4+3.2) (p=0.013). The propofol doses in group 2 were significantly lower than in group 1 (110.6+14.8 vs. 153.5+21.5) (p <0.001). Patients in group 2 required significantly more induction time than group 1 (146.9+42.3 vs. 103.4+33.6 (p <0.001). Conclusion: Propofol induction with TCI provided equal success rate as compared with standard bolus propofol induction for LMA insertion and insertion quality score. TCI significantly lowered the propofol consumption when compared with the standard 2.5 mg/kg propofol dose.

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 .

Comparison of effects of propofol and ketamine-propofol mixture (ketofol) on laryngeal mask airway insertion conditions and hemodynamics in elderly patients: a randomized, prospective, double-blind trial

PURPOSE

The objective of this study was to compare the effects of ketamine-propofol mixture (ketofol) and propofol on ProSeal laryngeal mask airway (PLMA) insertion conditions and hemodynamics in elderly patients.

METHODS

Eighty elderly patients, American Society of Anesthesiologists (ASA) physical status I and II, were randomly divided into two groups to receive either propofol 0.15 ml/kg (n = 40), or ketofol (using a 1:1 single-syringe mixture of 5 mg/ml ketamine and 5 mg/ml propofol) (n = 40) before induction of anesthesia. Sixty seconds after induction, the PLMA was inserted. Heart rate and arterial blood pressure (systolic [S] BP) were recorded prior to the induction of anesthesia, immediately following induction, immediately after PLMA insertion, and 5 and 10 min after PLMA insertion. PLMA insertion conditions were scored according to mouth opening, swallowing, coughing, head and body motion, laryngospasm, and ease of PLMA insertion by the same experienced anesthesiologist, who did not know which agents were used.

RESULTS

There were no differences in PLMA insertion conditions between the groups. The number of patients in need of ephedrine (P = 0.043) and the total dose of ephedrine (P = 0.022) were significantly lower, and apnea duration (P < 0.001) was significantly higher in the ketofol group compared with the propofol group. SBP was significantly higher in the ketofol group than in the propofol group immediately after PLMA insertion and 5 min after PLMA insertion.

CONCLUSIONS

The same PLMA insertion conditions were found with ketofol and propofol. The number of patients in need of ephedrine and the total ephedrine dose were lower and apnea duration was increased in the ketofol group.

Pretreatment with small-dose ketamine reduces predicted effect-site concentration of propofol required for loss of consciousness and Laryngeal Mask Airway insertion in women

STUDY OBJECTIVE

To investigate the effect of small-dose ketamine on the predicted effect-site concentration of propofol required for loss of consciousness (LOC) and Laryngeal Mask Airway (LMA) insertion.

DESIGN

Randomized, double-blinded study.

SETTINGS

Operating room.

PATIENTS

50 ASA physical status 1 and 2 women scheduled for elective breast or gynecological surgery.

INTERVENTIONS

Patients were randomly allocated to a ketamine group or a control group. Thirty seconds before propofol injection, ketamine group patients received ketamine 0.2 mg/kg, while control group patients received saline. Propofol was given in a target-controlled infusion and target blood concentration was gradually increased until LOC. The effect-site concentrations for attempting LMA insertion was predetermined by modifying Dixon's up and down method. LMA insertion was attempted without muscular blocking agents.

MEASUREMENTS

Pain scores on propofol injection, effect-site concentrations at LOC, hemodynamic variables, and patient movement or side effects on LMA insertion were recorded.

MAIN RESULTS

The effect-site concentration of propofol required for LOC was 2.14 μg/mL for the control group and 1.66 for the ketamine group (P = 0.0082). The predicted effect-site concentration of propofol alone at which 50% of patients did not move with LMA insertion (EC(50)LMI) was 3.59 μg/mL (95% CI: 3.18 ∼ 4.19 μg/mL). Pretreatment with ketamine 0.2 mg/kg decreased EC(50)LMI from 3.59 (3.18 ∼ 4.19) to 2.39 (1.22 ∼ 2.99).

CONCLUSIONS

Pretreatment with ketamine 0.2 mg/kg reduced the propofol concentration required for both LOC (22%) and LMA insertion (33%) in women.

Lidocaine given intravenously improves conditions for laryngeal mask airway insertion during propofol target-controlled infusion

BACKGROUND AND OBJECTIVE

Patient response to laryngeal mask airway insertion during propofol induction depends on many factors. Lidocaine has been used to reduce cardiovascular responses, coughing, and bucking induced by tracheal intubation. The aim of this study was to determine the effects of intravenous lidocaine on laryngeal mask airway insertion conditions during the induction of anaesthesia with propofol target-controlled infusion.

METHODS

Eighty patients, 16-54 years of age, weighing between 45 and 100 kg, who underwent minor surgery, were randomly divided into two groups (the lidocaine and control groups). Anaesthesia was induced with propofol target-controlled infusion at a target plasma concentration of 6 microg ml. The lidocaine group received 1.5 mg kg of lidocaine 50 s after starting target-controlled infusion and the control group received an equivalent volume of saline. Laryngeal mask airways were inserted when propofol effect-site concentrations reached 2.5 microg ml. Laryngeal mask airway insertion conditions (mouth opening, gagging, coughing, movements, laryngospasm, overall ease of insertion, and hiccups) were assessed, and haemodynamic responses were monitored for 3 min after laryngeal mask airway insertion.

RESULTS

No significant differences were observed between the two groups in terms of haemodynamic responses. However, the lidocaine group showed lower incidences of coughing (5 vs. 22.5%), gagging (25 vs. 55%), and laryngospasm (2.5 vs. 17.5%) (P < 0.05).

CONCLUSION

Pretreatment with intravenous lidocaine 1.5 mg kg during induction with propofol target-controlled infusion improves laryngeal mask airway insertion conditions.

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.

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.

Effect of nitrous oxide on propofol requirement during target-controlled infusion for oocyte retrieval

BACKGROUND

Oocyte (egg) retrieval for in-vitro fertilization is a relatively short procedure, usually performed as an outpatient. Propofol is a suitable anesthetic agent. Target-controlled infusion is a recently developed system that aids rapid recovery from propofol anesthesia. This study sought to determine the target concentration of propofol required to prevent movement in 50% (Cp50) and 95% (Cp95) of women during oocyte retrieval, and investigated whether supplemental nitrous oxide (N2O) modified the Cp50 and Cp95.

METHODS

Forty-seven women scheduled for oocyte retrieval were randomly selected to receive either O2-air mixture (control group; n = 23) or 50% O2-N2O mixture (Nitrous oxide group; n = 24). Propofol was infused using a target-controlled infusion system with the concentration determined by up-down sequential allocation using 0.5 microg/mL step size. Transvaginal oocyte retrieval was performed after reaching target blood concentration. Patient responses to oocyte retrieval were noted as either no movement or movement.

RESULTS

Using target-controlled infusion the Cp50 was 4.1 microg/mL in the control group and 3.3 microg/mL in the nitrous oxide group. Calculated Cp95 values were 4.0 microg/mL and 5.1 microg/mL with and without 50% nitrous oxide respectively.

CONCLUSIONS

The Cp50 value for target-controlled infusion propofol during oocyte retrieval was significantly reduced by a factor of 1.24 (95% CI 1.07-1.44) with the use of 50% nitrous oxide.

Propofol concentration requirement for laryngeal mask airway insertion was highest with the ProSeal, next highest with the Fastrach, and lowest with the Classic type, with target-controlled infusion

STUDY OBJECTIVE

To determine propofol concentration of plasma 50% (Cp50, concentration at which there is a 50% chance that patients show no movement in response) for the Classic-, Fastrach-, and ProSeal-type laryngeal mask airway (LMA) insertion using target-controlled infusion (TCI) technique.

DESIGN

Prospective, randomized, comparative study.

SETTING

University-affiliated hospital.

PATIENTS

Sixty American Society of Anesthesiologists physical status I and II women scheduled for minor gynecologic operations.

INTERVENTIONS

Propofol TCI (Diprifusor pharmacokinetic model) was started at target concentration using an anesthesia pump. After reaching target effect-site concentration of propofol, 1 of the 3 types of LMA was inserted. We recorded patient responses to LMA insertion as "movement" or "no movement." Test propofol concentrations started from a dosage of 4 microg/mL. Concentrations were then predetermined by a modified Dixon's up-and-down method with 0.4 microg/mL step size.

MEASUREMENTS

Patient response to LMA insertion was classified as either of "no movement" or "movement." The midpoint was defined as the average concentration value of crossover (movement/no movement) response. The Cp50 value was defined as the average of the crossover midpoints in each group, and it was estimated from calculating the midpoints.

MAIN RESULTS

Cp50 of the Classic, Fastrach, and ProSeal LMA insertion were 3.2+/-0.34, 4.0+/-0.22, and 4.9+/-0.20 microg/mL (mean+/-SD), respectively.

CONCLUSION

Required propofol TCI concentrations for LMA insertion were significantly highest for the ProSeal, second highest for the Fastrach, and lowest for the Classic LMA.

Predicted values of propofol EC50 and sevoflurane concentration for insertion of laryngeal mask Classic and ProSeal

BACKGROUND

A new laryngeal mask airway, the ProSeal (PLMA), is said to be more difficult to insert than the laryngeal mask airway Classic (CLMA) using propofol anaesthesia. Therefore, we expected a greater dose of propofol and sevoflurane to be required to insert the PLMA compared with the CLMA. We determined the effective concentration 50% (EC(50)) of propofol and end-tidal sevoflurane to allow insertion of the PLMA and the CLMA.

METHODS

Seventy-six elective female patients (aged 20-60 yr and ASA I-II) were randomly assigned to one of four groups. Either a PLMA or a CLMA was inserted using either propofol target controlled infusion or sevoflurane. Both propofol and sevoflurane targets were determined with a modified Dixon's up-and-down method. After equilibration between the predetermined blood and effect site concentrations, which had been held steady for more than 10 min, LMA insertion was attempted without neuromuscular block.

RESULTS

The predicted EC(50CLMA) and EC(50PLMA) for propofol were 3.14 (0.33) and 4.32 (0.67) micro g ml(-1). E'(CLMA) and E'(PLMA) of sevoflurane (mean (SD)) were 2.36 (0.22) and 2.82 (0.45)% (P<0.01 and 0.05, respectively).

CONCLUSIONS

The estimated concentration of propofol and the sevoflurane concentration needed to allow insertion of the ProSeal are respectively 38 and 20% greater than those needed for insertion of the Classic LMA.