Minimum anesthetic concentration of sevoflurane with different xenon concentrations in swine.
In a previous study, we described a partial antagonism of xenon (Xe) in combination with isoflurane. One hypothetical explanation suggested that Xe and isoflurane probably induced anesthesia via different pathways at the neuronal level. This warranted investigating the combination of Xe with other inhaled anesthetics to examine the relationship between Xe and volatile anesthetics in general. We therefore investigated the influence of Xe on the minimum alveolar concentration (MAC) of sevoflurane. The study was performed in 10 swine (weight 30.8 kg +/- 2.6, mean +/- SD) ventilated with xenon 0%, 15%, 30%, 40%, 50%, and 65% in oxygen. At each Xe concentration, various concentrations of sevoflurane were administered in a stepwise design. For each a supramaximal pain stimulus (claw clamp) was applied. The appearance of a withdrawal reaction was recorded. The sevoflurane MAC was defined as the end-tidal concentration required to produce a 50% response rate. At each Xe concentration, the animals' responses to the pain stimulus were categorized and a logistic regression model was fitted to the results to determine sevoflurane MAC. Sevoflurane MAC was decreased by inhalation of Xe in a linear manner from 2.53 with 0% Xe to 1.54 with 65% Xe. In contrast to Xe and isoflurane, the anesthetic effects of Xe and sevoflurane appear to be simply linear.


CONCLUSIONS
We investigated the influence of the anesthetic gas, xenon, on the minimum alveolar concentration (MAC) for the volatile anesthetic sevoflurane. The study was performed in 10 swine ventilated with fixed xenon and various concentrations of isoflurane. The sevoflurane MAC is decreased by inhalation of xenon in a linear relationship.
Departments of *Anesthesiology and †Medical Statistics, Universitätsklinikum der RWTH Aachen, Aachen, Germany, and the ‡Department of Anesthesiology and Intensive Care, Waldkrankenhaus Berlin, Berlin, Germany.
Klaus E
KE
Hecker
Jan H
JH
Baumert
Nicola
N
Horn
Matthias
M
Reyle-Hahn
Nicole
N
Heussen
Rolf
R
Rossaint
D000465:Algorithms; D018685:Anesthetics, Inhalation / Q000008:administration & dosage; D000818:Animals; D001784:Blood Gas Analysis; D004347:Drug Interactions; D005260:Female; D006439:Hemodynamics / Q000187:drug effects; D016015:Logistic Models; D008738:Methyl Ethers / Q000008:administration & dosage; D011188:Potassium / Q000097:blood; D011650:Pulmonary Alveoli / Q000378:metabolism; D011659:Pulmonary Gas Exchange / Q000187:drug effects; D012121:Respiration, Artificial; D000077149:Sevoflurane; D012964:Sodium / Q000097:blood; D013552:Swine; D014978:Xenon / Q000008:administration & dosage
D018685:Anesthetics, Inhalation; D008738:Methyl Ethers; D000077149:Sevoflurane; D014978:Xenon; D012964:Sodium; D011188:Potassium