Awakening concentrations of isoflurane are not affected by analgesic doses of morphine.
A randomized, double-blind study was performed to determine how morphine 0.1 mg/kg IV, or placebo administered 80 +/- 11 (means +/- SE) minutes before the end of surgery affect recovery from isoflurane/oxygen anesthesia. End-tidal isoflurane remained constant at 1.10 +/- 0.02% (means +/- SE) in both groups intraoperatively, and no other anesthetics were given after the administration of the morphine or placebo. Duration of anesthesia did not differ significantly between the morphine (172 +/- 7 minutes) and placebo (163 +/- 18 minutes) groups. Times from discontinuation of isoflurane until eye-opening in response to verbal command were similar in the morphine (19 +/- 2 minutes) and placebo (22 +/- 3 minutes) groups. At the time of eye-opening, end-tidal isoflurane concentrations did not differ between subjects receiving morphine (0.20 +/- 0.02%) and placebo (0.18 +/- 0.01%). It is concluded that the awakening concentration (MAC-awake) during recovery from isoflurane anesthesia is approximately 0.19% and is not affected by analgesic doses or morphine.
Gross
J B
JB
Department of Anesthesia, University of Pennsylvania, Philadelphia.
Alexander
C M
CM
D000328:Adult; D000375:Aging / Q000187:drug effects; D000762:Anesthesia Recovery Period; D000769:Anesthesia, Inhalation / Q000379:methods; D002986:Clinical Trials as Topic; D004311:Double-Blind Method; D004347:Drug Interactions; D006801:Humans; D007530:Isoflurane / Q000008:administration & dosage*; D008875:Middle Aged; D009020:Morphine / Q000008:administration & dosage*; D011897:Random Allocation; D013874:Thiopental; D013997:Time Factors; D014851:Wakefulness / Q000187:drug effects*
D009020:Morphine; D007530:Isoflurane; D013874:Thiopental