Alfentanil dosage when inserting the classic laryngeal mask airway.
BACKGROUND
The purpose of this study was to determine an optimum dose of alfentanil, coadministered with 2.5 mg/kg propofol, when inserting a classic laryngeal mask airway.


METHODS
Seventy-five adult ethnic Chinese patients with an American Society of Anesthesiologists physiologic status classification I or II and requiring anesthesia for minor surgery with a laryngeal mask were recruited. They were randomly assigned to five dosage groups: placebo or 5, 10, 15, or 20 microg/kg. The study drug plus propofol were administered, and 90 s later, insertion conditions were assessed using a six-category score. The duration of apnea was recorded. A probit analysis was performed and used to estimate the ED50 and ED95 with 95% confidence intervals for each assessment.


RESULTS
Twenty-five male and 50 female patients, aged 18-59 yr, were studied. The five groups were similar. Laryngeal mask insertion was successful in all but one alfentanil patient. Duration of apnea increased with increasing dosage of alfentanil to over 5 min (P < 0.001). Dose-responses could not be predicted for categories of resistance to mouth opening and to insertion. For the other four categories, swallowing, gagging, movement, and laryngospasm, ED50 and ED95 with confidence intervals for alfentanil could be determined.


CONCLUSIONS
The optimum dose for alfentanil, when coadministered with 2.5 mg/kg propofol, was 10 microg/kg.
Yu
Andrea L Y
AL
Department of Anaesthesia and Intensive Care, The Chinese University of Hong Kong, Prince of Wales Hospital, Shatin, New Territories, Hong Kong.
Critchley
Lester A H
LA
Lee
Anna
A
Gin
Tony
T
D000293:Adolescent; D000328:Adult; D015760:Alfentanil / Q000008:administration & dosage*; D000768:Anesthesia, General; D018686:Anesthetics, Intravenous / Q000008:administration & dosage*; D001049:Apnea / Q000503:physiopathology; D003627:Data Interpretation, Statistical; D004305:Dose-Response Relationship, Drug; D005260:Female; D006439:Hemodynamics / Q000187:drug effects; D006801:Humans; D017214:Laryngeal Masks / Q000009:adverse effects; D008297:Male; D008875:Middle Aged; D015742:Propofol / Q000008:administration & dosage; D012129:Respiratory Function Tests
D018686:Anesthetics, Intravenous; D015760:Alfentanil; D015742:Propofol