Relation between fentanyl dose and predicted EC50 of propofol for laryngeal mask insertion.
BACKGROUND
This study sought to determine the effective concentration for 50% of the attempts to secure laryngeal mask insertion (predicted EC(50LMA)) of propofol using a target-controlled infusion (Diprifusor) and investigated whether fentanyl influenced these required concentrations, respiratory rate (RR) and bispectral index (BIS).


METHODS
Sixty-four elective unpremedicated patients were randomly assigned to four groups (n = 16 for each group) and given saline (control) or fentanyl 0.5, 1 or 2 micro g kg(-1). Propofol target concentration was determined by a modification of Dixon's up-and-down method. Laryngeal mask airway insertion was attempted without neuromuscular blocking drugs after equilibration had been established for >10 min. Movement was defined as presence of bucking or gross purposeful muscular movement within 1 min after insertion. EC(50LMA) values were obtained by calculating the mean of 16 patients in each group.


RESULTS
Predicted EC(50LMA) of the control, fentanyl 0.5, 1 and 2 micro g kg(-1) groups were 3.25 (0.20), 2.06 (0.55), 1.69 (0.38) and 1.50 (0.54) micro g ml(-1) respectively; those of all fentanyl groups were significantly lower than that of control. RR was decreased in relation to the fentanyl dose up to 1 micro g kg(-1). BIS values after fentanyl 1 and 2 micro g kg(-1) were significantly greater than in the control and 0.5 micro g kg(-1) groups.


CONCLUSIONS
A fentanyl dose of 0.5 micro g kg(-1) is sufficient to decrease predicted EC(50LMA) with minimum respiratory depression and without a high BIS value.
Kodaka
M
M
Department of Anesthesiology, Saitama Medical Center, Saitama Medical School, 1981, Tsujido-cho, Kamoda, Kawagoe, Saitama 350-8550, Japan. kmkodaka@cb3.so-net.ne.jp
Okamoto
Y
Y
Handa
F
F
Kawasaki
J
J
Miyao
H
H
D000759:Adjuvants, Anesthesia / Q000008:administration & dosage*; D000328:Adult; D000701:Analgesics, Opioid / Q000008:administration & dosage; D018686:Anesthetics, Intravenous / Q000008:administration & dosage*; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D004569:Electroencephalography / Q000187:drug effects; D005260:Female; D005283:Fentanyl / Q000008:administration & dosage*; D006439:Hemodynamics / Q000187:drug effects; D006801:Humans; D017214:Laryngeal Masks; D008875:Middle Aged; D015742:Propofol / Q000008:administration & dosage*; D012119:Respiration / Q000187:drug effects
D000759:Adjuvants, Anesthesia; D000701:Analgesics, Opioid; D018686:Anesthetics, Intravenous; D005283:Fentanyl; D015742:Propofol