Effect of sex differences in remifentanil requirements for the insertion of a laryngeal mask airway during propofol anesthesia: A prospective randomized trial.
BACKGROUND
Remifentanil can improve insertion of a laryngeal mask airway (LMA) during induction with propofol. Recently, it has been suggested that there is a sex difference in opioid requirements for this procedure. The purposes of this study were to determine the effective effect-site concentration (Ce) of remifentanil for the facilitation of LMA insertion in male and female patients during propofol anesthesia without neuromuscular blockade and to evaluate whether there are sex differences in the Ce of remifentanil required for successful LMA insertion.


METHODS
Forty-eight patients (24 male, 24 female) with American Society of Anesthesiologists physical status 1 or 2, aged 20 to 60 years, scheduled for minor orthopedic surgery under general anesthesia were enrolled. Anesthesia was induced by target-controlled infusion (TCI) of propofol and remifentanil. The target Ce of propofol was 5 μg/mL initially and was reduced to 3.5 μg/mL after loss of consciousness. The Ce of remifentanil given to each patient was determined by the response of the previously tested patient using 0.5 ng/mL as a step size. The 1st patient was tested at a Ce of 3.0 ng/mL of remifentanil. Successful LMA insertion was defined as smooth insertion without patient movement or significant resistance to mouth opening.


RESULTS
The effective Ce of remifentanil required for successful LMA insertion on 50% of occasions (effective effect-site concentration for 50% [EC50]) as estimated by Dixon method was significantly lower in women (2.18 ± 0.35 ng/mL) than in men (2.82 ± 0.53 ng/mL) (P = 0.02). Using the isotonic regression method, the effective Ce of remifentanil required for successful LMA insertion on 95% of occasions (EC95) (95% confidence interval [CI]) was significantly lower in women (3.38 [3.0-3.48] ng/mL) than in men (3.94 [3.80-3.98] ng/mL).


CONCLUSIONS
The Ce of remifentanil required to facilitate successful LMA insertion is higher during propofol induction by TCI in men than in women. When using remifentanil for LMA insertion, patient sex should be taken into account for appropriate dosing.
aDepartment of Anesthesiology and Pain Medicine, Ajou University School of Medicine, World Cup-ro, Yeongtong-gu, Suwon bDepartment of Anesthesiology and Pain Medicine, Gachon University, Gil Medical Center, Namdong-gu, Incheon, Republic of Korea.
Han Bum
HB
Joe
Jong Yeop
JY
Kim
Hyun Jeong
HJ
Kwak
Sang Eon
SE
Oh
Sook Young
SY
Lee
Sung Yong
SY
Park
D000368:Aged; D000771:Anesthesia, Intravenous / Q000379:methods*; D018686:Anesthetics, Intravenous / Q000008:administration & dosage; D004305:Dose-Response Relationship, Drug; D004359:Drug Therapy, Combination; D005260:Female; D006801:Humans; D017214:Laryngeal Masks; D008297:Male; D008875:Middle Aged; D019637:Orthopedic Procedures; D010880:Piperidines / Q000008:administration & dosage*; D015742:Propofol / Q000008:administration & dosage*; D011446:Prospective Studies; D000077208:Remifentanil; D012737:Sex Factors
D018686:Anesthetics, Intravenous; D010880:Piperidines; D000077208:Remifentanil; D015742:Propofol
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