Preoperative Dexmedetomidine & EC50 of Propofol
Condition: Urologic Surgery
Study type: Interventional
Phase: Phase 4

Summary: 
      Dexmedetomidine is a useful anaesthetic adjuvant for general anaesthesia. In this prospective
      randomised study, we determined whether preoperative dexmedetomidine administration could
      reduce the half maximal effective concentration (EC50) of propofol for successful i-gelTM
      insertion without muscle relaxants.
    

Detailed description: 
      Propofol is a useful induction agent for LMA insertion without muscle relaxants because it
      profoundly inhibits pharyngeal and laryngeal reactivity. A previous report showed that the
      effect-site concentration of propofol for successful classic LMA insertion in 50% of adults
      (EC50) without muscle relaxants in healthy male patients was 8.72 (0.55) µg ml-1. The EC50 of
      propofol may be dependent on the type of LMA used. A previous study comparing the EC50 of the
      propofol concentration between classic and proseal LMA insertions demonstrated that the EC50
      of propofol needed for proseal LMA insertion was 35% greater than that needed for classic LMA
      insertion. Unfortunately, no investigation has been performed to determine the EC50 of the
      propofol concentration required for i-gel insertion without muscle relaxants.

      Dexmedetomidine (DEX), a selective alpha-2 agonist, has sympatholytic, sedative, and
      analgesic properties. Such beneficial characteristics make DEX a useful anaesthetic adjuvant
      for general anaesthesia. Many reports have revealed the beneficial effects of DEX in terms of
      reducing intraoperative anaesthetic requirements, postoperative analgesic demand, and
      increased haemodynamic responses to noxious stimuli such as endotracheal intubation. A
      previous investigation showed that preoperative clonidine, an alpha-2 agonist, decreased the
      EC50 required for LMA insertion.

      We hypothesised that preoperative DEX administration can reduce the propofol concentration
      required for i-gel insertion. In this study, we compared the EC50 of propofol needed for
      successful i-gel insertion without muscle relaxants between DEX and placebo groups
    

Intervention name(s): Group C : Saline + propofol group; Group D : Dexmedetomidine + propofol group
Intervention type(s): Drug; Drug
Intervention description(s): All patients were pre-oxygenated with 100% oxygen with spontaneous breathing for 3 min before the end of loading of normal saline. Anaesthesia was induced with predetermined effect-site propofol concentrations using a target-controlled infusion device (Orchestra; Fresenius-Vial, Brezins, France). The first patient in Group C received an effect-site propofol concentration of 3 and 5 µg mL-1, respectively, over 5 min.
After equilibration of the plasma and effect-site propofol concentrations, i-gel (size 4 for patients weighing 50-90 kg, size 3 for patients weighing 30-50 kg) was inserted using the standard technique by a single anaesthesiologist staff member with expertise in i-gel insertion and who entered the operating room immediately before i-gel insertion to blind him to the group assignment; All patients were pre-oxygenated with 100% oxygen with spontaneous breathing for 3 min before the end of loading of dexmedetomidine. Anaesthesia was induced with predetermined effect-site propofol concentrations using a target-controlled infusion device (Orchestra; Fresenius-Vial, Brezins, France). The first patient in Group D received an effect-site propofol concentration of 3 and 5 µg mL-1, respectively, over 5 min.
After equilibration of the plasma and effect-site propofol concentrations, i-gel (size 4 for patients weighing 50-90 kg, size 3 for patients weighing 30-50 kg) was inserted using the standard technique by a single anaesthesiologist staff member with expertise in i-gel insertion and who entered the operating room immediately before i-gel insertion to blind him to the group assignment.
Intervention MeSH terms: Dexmedetomidine; Propofol
Allocation: Randomized
Intervention model: Single Group Assignment
Masking: Triple (Care Provider, Investigator, Outcomes Assessor)
Primary purpose: Supportive Care