Sevoflurane-remifentanil EC50 (The 50% Effective Concentration) Values for LMA-Supreme Versus LMA ProSeal Insertion
Condition: Sevoflurane
Study type: Interventional
Phase: Phase 4

Summary: 
      The study was designed to determine and compare the sevoflurane EC50 optimal concentration
      for laryngeal mask airway Supreme versus laryngeal mask airway ProSeal insertion during
      target-controlled infusion of remifentanil.
    

Detailed description: 
      Since the introduction of the laryngeal mask airway (LMA), a number of new supraglottic
      airway devices as the LMA-Supreme (LMAS) and the LMA ProSeal (LMAP) have been developed for
      the management of the airway during general anesthesia, and specifically in the context of
      day surgery. ProSeal laryngeal mask airway is a reusable device designed to separate the
      gastrointestinal and respiratory tracts, thereby improving the airway seal pressure and
      allowing for controlled ventilation more efficiently tan classic LMA. The LMAS was developed
      in 2007 as a single-use device provided with gastric canal, and combine the features of both
      intubating LMA and the LMAP. Recently, there has been a growing interest in these devices
      because of favourable studies obtained in several anaesthetic contexts that have proven their
      effectiveness and safety. Even though insertion of both devices were associated with a higher
      initial success rate, fewer airway manipulations and a safe and effective airway during
      anaesthesia, the anaesthetic techniques for its insertion were not standardised. Most
      available data on the requirements of anaesthetic drugs and co-induction agents used for
      insertion of both devices originate from research involving other assessments of the LMAs
      such as the seal respiratory and gastrointestinal tract. Investigators tested for differences
      in the predicted concentration of sevoflurane with remifentanil for the insertion of the LMAS
      vs. LMAP.

      Methods: 45 patients American Society of Anesthesiologists (ASA) class I or II aged 20-60
      years undergoing ambulatory elective surgery were randomized to either the LMAS or LMAP. The
      patients were premedicated with midazolam 1 mg iv before surgery. All patients were
      preoxygenated using 100% oxygen with a normal tidal volumen for 3 min. The circuit was primed
      with sevoflurane 5% at a fresh gas flow of 6 L/min for 1 min. Anaesthesia was induced with
      inhaled sevoflurane up to 5% in oxygen via facemask with fresh gas flow at 6 L/min.
      Simultaneously remifentanil at an effect-site of 4 ng/ml was started. Target-controlled
      infusions was used (Alaris PK) for remifentanil administration. After loss of consciousness,
      the inspired concentration of sevoflurane was changed to obtain a predetermined end-tidal
      concentration. A single experienced anaesthetist in the use of supraglottic devices inserted
      the devices according to the manufacturer's recommendations. The LMAs size was chosen
      according to the sex of the patients, size 4 for women and size 5 for men; however for
      patients weighing ≤50 kg a size 3 was inserted. Neuromuscular blocking agents were not given.
      Two nurses, who were blinded to the anaesthetic concentration, classified responses by the
      patient to LMA insertion as either "movement" or "not movement". Assesment was made for jaw
      relaxation and graded with Muzi score. A Muzi score >2 was defined as a failure of insertion.
      The end-tidal (ET) sevoflurane concentration used for each patient was determined using the
      Dixon's up-and-down method. The ratio of the end-tidal to predetermined end-tidal
      concentrations was maintained at 0.9-1.0 for at least 10 minutes to establish equilibration
      before device insertion was attempted. The first patient received a 2.5% sevoflurane
      concentration and the step size of increase/decrease was 0.5%. If the supraglottic device
      (LMAS or LMAP) insertion was successful, sevoflurane concentration for the next patient was
      decrease by 0.5%. If not, sevoflurane concentration was increased by the same amount for the
      next patient. For their comfort, patients experiencing movement received a 1-2 mg/kg bolus
      dose of propofol.
    

Intervention name(s): laryngeal mask supreme; laryngeal mask proseal
Intervention type(s): Device; Device
Intervention description(s): Sevoflurane was administered by facial mask with concomitant remifentanil administration (at an effect-site of 4 ng/ml). The LMAS was inserted according to the manufacturer's recommendations with the patient's head in the neutral position. After equilibrium the LMAS was inserted and secured according to the manufacturer's recommendations, without using muscle relaxants. A single measurement will be obtained from each patient. If the patient reacted with movement, a 1-2 mg/kg dose of Propofol was administered.; Sevoflurane was administered by facial mask with concomitant remifentanil administration (at an effect-site of 4 ng/ml).The LMAP was inserted according to the manufacturer's recommendations with the patient's head in the neutral position. After equilibrium the LMAP was inserted and secured according to the manufacturer's recommendations, without using muscle relaxants. A single measurement will be obtained from each patient. If the patient reacted with movement, a 1-2 mg/kg dose of Propofol was administered.
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Double (Participant, Investigator)
Primary purpose: Treatment
Keywords: Sevoflurane; Remifentanil; Laryngeal mask supreme; laryngeal mask proseal