title: Comparison of remifentanil EC50 for facilitating i-gel and laryngeal mask airway insertion with propofol anesthesia.
abstract: Each supraglottic airway requires different anesthetic depth because it has a specific structure and different compressive force in the oropharyngeal cavity. We designed the study to compare the effect-site concentration (Ce) of remifentanil in 50 % of patients (EC50) for successful insertion of the i-gel second-generation supraglottic airway device with that for laryngeal mask airway (LMA) insertion during target-controlled infusion (TCI) of propofol.
  
  
  
  Forty-one female patients were randomized to the i-gel group (n = 20) or the LMA group (n = 21). Anesthesia was induced with propofol Ce of 5 μg/ml and the predetermined remifentanil Ce, and the i-gel or LMA was inserted 5 min later. The remifentanil Ce was estimated by modified Dixon's up-and-down method (initial concentration: 3.0 ng/ml, step size: 0.5 ng/ml). The patient's response to device insertion was classified as either "success (no movement)" or "failure (movement)".
  
  
  
  Using the Dixon's up-and-down method, EC50 of remifentanil Ce for the i-gel (1.58 ± 0.41 ng/ml) was significantly lower than that for LMA (2.25 ± 0.55 ng/ml) (p = 0.038). Using isotonic regression, EC50 (83 % CI) of remifentanil in the i-gel group [1.50 (1.37-1.80) ng/ml] was statistically lower than that in the LMA group [2.00 (1.82-2.34) ng/ml]. EC95 (95 % CI) of remifentanil in the i-gel group [2.38 (1.48-2.50) ng/ml] was statistically lower than that in the LMA group [3.35 (2.58-3.48) ng/ml].
  
  
  
  We found that EC50 of remifentanil Ce for i-gel insertion (1.58 ng/ml) was significantly lower than that for LMA insertion (2.25 ng/ml) in female patients during propofol TCI without neuromuscular blockade.
authors.affiliation: Department of Anesthesiology and Pain Medicine, Anesthesia and Pain Research Institute, Yonsei University College of Medicine, Seoul, Korea.
authors.forename: Jong Bum
authors.initials: JB
authors.lastname: Choi
authors.affiliation: Department of Anesthesiology and Pain Medicine, Gil Medical Center, Gachon University, Incheon, Korea.
authors.forename: Hyun Jeong
authors.initials: HJ
authors.lastname: Kwak
authors.affiliation: Department of Anesthesiology and Pain Medicine, Gil Medical Center, Gachon University, Incheon, Korea.
authors.forename: Kyung Cheon
authors.initials: KC
authors.lastname: Lee
authors.affiliation: Department of Anesthesiology and Pain Medicine, Ajou University School of Medicine, San 5, Wonchon-dong, Yeongtong-gu, Suwon, 443-721, Korea.
authors.forename: Se Ryeon
authors.initials: SR
authors.lastname: Lee
authors.affiliation: Department of Anesthesiology and Pain Medicine, Ajou University School of Medicine, San 5, Wonchon-dong, Yeongtong-gu, Suwon, 443-721, Korea.
authors.forename: Sook Young
authors.initials: SY
authors.lastname: Lee
authors.affiliation: Department of Anesthesiology and Pain Medicine, Ajou University School of Medicine, San 5, Wonchon-dong, Yeongtong-gu, Suwon, 443-721, Korea. kjyeop@ajou.ac.kr.
authors.forename: Jong Yeop
authors.initials: JY
authors.lastname: Kim
mesh_terms: D000328:Adult; D000758:Anesthesia / Q000379:methods; D018686:Anesthetics, Intravenous / Q000008:administration & dosage; D005260:Female; D006801:Humans; D017214:Laryngeal Masks; D008875:Middle Aged; D019148:Neuromuscular Blockade / Q000379:methods; D010880:Piperidines / Q000008:administration & dosage*; D011312:Pressure; D015742:Propofol / Q000008:administration & dosage*; D000077208:Remifentanil
chemical_list: D018686:Anesthetics, Intravenous; D010880:Piperidines; D000077208:Remifentanil; D015742:Propofol
keywords: Laryngeal mask airway; Remifentanil; i-gel