MAC-Wert-Bestimmung von Sevofluran bei unterschiedlichen Xenonkonzentrationen an 10 Schweinen

For patients requiring a fraction of inspired oxygen more than 0.3, the use of xenon (Xe) as the sole anesthetic is limited because of its large minimum alveolar anesthetic concentration (MAC) of 63,1%. This warrants investigating the combination of Xe with other inhaled anesthetics. In the existing literature, the reported relationships between the effects of volatile and gaseous anesthetics are not uniform. The basic question whether such combinations will act additively or show partial antagonism has not been answered in general. Because of the reported favorable properties of xenon (Xe), investigating the combined effects of Xe and volatile anesthetics is warranted. A few studies described a linear relationship between Xe and sevoflurane or halothane in humans. On the other hand, a partial antagonistic is shown for xenon and isoflurane in swine.We therefore investigated the influence of Xe on the MAC of sevoflurane. The study was performed in 10 swine (weight 30.8 kg, ± 2.6 SD) ventilated with Xenon 0%, 15%, 30%, 40%, 50%, 65% in oxygen. The animals were premedicated with Azaperone 4 mg/kg IM, an ear vein was cannulated with an 18- or 20-gauge Teflon cannula. Anesthesia was induced by injection of Propofol 2 mg/kg. The lungs of the pigs were mechanically ventilated using a Draeger PhysioFlex closed circuit ventilator. The experiments which lasted 8-10 hours, were started at least 3 hours after premedication. With each xenon concentration, various concentrations of sevoflurane were administered in a step-wise 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 xenon 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 xenon from 2.30% with Xe 15%, 2.08% with Xe 30%, 1.92% with Xe 40%, 1.77% with Xe 50% to 1.54% with Xe 65%. The MAC of Sevoflurane in absence of Xe was 2.53% (2.23;2.83) like Monahar showed before in 1984. The interaction coefficient (ß12) between sevoflurane and Xe was not significantly different from zero (P = 0.0898), indicating that Xe has a linear rather than a non-linear effect on reducing sevoflurane requirements.

Grantor dc:publisher

Publikationsserver der RWTH Aachen University

Year dc:date

2004

Author dc:creator

• Rinkens, Thorsten

Contributors dc:contributor

• Rossaint, Rolf

• info:eu-repo/classification/ddc/610
• Medizin
• MAC
• Sevofluran
• Xenon

Statement dc:rights

• info:eu-repo/semantics/openAccess

Language dc:language

ger

Identifier

https://publications.rwth-aachen.de/search?p=id:%22RWTH-CONV-121249%22

OAI identifier oai:identifier

oai:publications.rwth-aachen.de:59468