Concentrations of desflurane and propofol that suppress response to command in humans.
The anesthetic concentration just suppressing appropriate response to command (minimum alveolar anesthetic concentration awake [MAC-awake] for volatile anesthetics or plasma concentration to prevent a response in 50% of patients [Cp50]-awake for intravenous anesthetics) provides three important measures. First, along with pharmacokinetics, the ratio of the awakening concentration to the anesthetizing concentration (MAC-awake/MAC or Cp50-awake/Cp50) determines time to awakening. Second, a correlation between MAC-awake and the anesthetic concentration sufficient to prevent learning suggests MAC-awake provides a surrogate measure of amnestic potency. Third, population values for MAC-awake provide evidence for or against commonality in anesthetic mechanisms. We studied 22 male volunteers twice to determine both MAC-awake for desflurane (2.60% +/- 0.46%) and Cp50-awake for propofol (2.69 +/- 0.56 microgram/mL). Awakening with desflurane occurs at a concentration closer to its anesthetizing concentration (36% of MAC) than propofol (18% of Cp50); that is, 1) desflurane requires less of a decrement in anesthetic concentration at the effect site for arousal; and 2) if MAC-awake (Cp50-awake) values reflect the concentrations providing amnesia, propofol is a more potent amnestic. Of interest, the dose response curves of desflurane and propofol were equivalently steep, a finding consistent with a common mechanism of action. In contrast, sensitivity of each volunteer to desflurane did not correlate with sensitivity to propofol (r2 < 0.01, P = 0.98) arguing against a common mechanism.
Chortkoff
B S
BS
Department of Anesthesia, University of California, San Francisco 94143-0648, USA.
Eger
E I
EI
Crankshaw
D P
DP
Gonsowski
C T
CT
Dutton
R C
RC
Ionescu
P
P
D000328:Adult; D000762:Anesthesia Recovery Period; D018685:Anesthetics, Inhalation / Q000008:administration & dosage / Q000494:pharmacology*; D018686:Anesthetics, Intravenous / Q000008:administration & dosage / Q000494:pharmacology*; D001143:Arousal / Q000187:drug effects*; D000077335:Desflurane; D006801:Humans; D007530:Isoflurane / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000494:pharmacology; D008297:Male; D008568:Memory / Q000187:drug effects; D015742:Propofol / Q000008:administration & dosage / Q000494:pharmacology*
D018685:Anesthetics, Inhalation; D018686:Anesthetics, Intravenous; D000077335:Desflurane; D007530:Isoflurane; D015742:Propofol