Tutorial: context-sensitive decrement times for inhaled anesthetics.
Context-sensitive decrement times for inhaled anesthetics connect two values: a) the duration of anesthesia (nominally at a constant alveolar concentration)-the "context" and b) the time to decrease the alveolar or vital tissue (e.g., brain, heart, kidney, and liver, collectively called the vessel-rich group of tissues) concentration by some fractional "decrement" of the starting concentration. Increasing duration of anesthesia increases the time to a given decrement in a nonlinear manner that may considerably delay recovery. In the present report we use a commercially available simulation program (Gas Man) to confirm and enlarge on these concepts. In this simulation, increasing duration of anesthesia can markedly delay complete awakening for isoflurane. Increasing anesthesia duration imposes considerably less delay in awakening from sevoflurane compared with isoflurane. For desflurane, only prolonged anesthesia or decrements of 95% and more should delay awakening from anesthesia. These changes are shown to be the result of the relative solubility of each anesthetic in blood and tissue. An increase in cardiac output is also shown to delay awakening.
Eger
Edmond I
EI
Department of Anesthesia and Perioperative Care, University of California, Department of Biopharmaceutical Science, UCSF, San Francisco, California, and Department of Anesthesia, Stanford University, Stanford, California.
Shafer
Steven L
SL
D000762:Anesthesia Recovery Period; D000769:Anesthesia, Inhalation; D018685:Anesthetics, Inhalation / Q000737:chemistry / Q000493:pharmacokinetics*; D001784:Blood Gas Analysis; D002302:Cardiac Output / Q000187:drug effects; D003198:Computer Simulation; D000077335:Desflurane; D006439:Hemodynamics / Q000187:drug effects; D006801:Humans; D007530:Isoflurane / Q000031:analogs & derivatives / Q000737:chemistry / Q000493:pharmacokinetics; D008738:Methyl Ethers / Q000737:chemistry / Q000493:pharmacokinetics; D008954:Models, Biological; D011650:Pulmonary Alveoli / Q000378:metabolism; D000077149:Sevoflurane; D012995:Solubility; D014018:Tissue Distribution
D018685:Anesthetics, Inhalation; D008738:Methyl Ethers; D000077149:Sevoflurane; D000077335:Desflurane; D007530:Isoflurane