[The interaction of nitrous oxide and enflurane on the EEG median of 2-3 Hz is additive, but weaker than at 1.0 MAC].
The aim of this study was to quantify the interaction of enflurane and nitrous oxide at a constant median EEG frequency.


METHODS
Thirty patients were studied during laparotomies. Nitrous oxide was randomly administered in concentrations of 0, 20, 40, 60, and 75 vol.-% for 10 patients for each nitrous oxide concentration. Enflurane vaporizer settings were chosen so that the median EEG frequency was kept constant at 2-3 Hz. The relationship between nitrous oxide concentrations and the required enflurane concentrations was examined with the isobole method.


RESULTS
Nitrous oxide decreases the enflurane requirement linearly. Addition of every 10 vol.-% of nitrous oxide decreases the enflurane requirement by 0.042 vol.-%. The total anaesthetic requirement of enflurane and nitrous oxide, expressed in terms of previously reported MAC values, increases significantly with increasing nitrous oxide concentrations.


CONCLUSIONS
The interaction of enflurane and nitrous oxide in the dose range from 0 to 75 vol.-% on median EEG frequency is compatible with additivity. The potency of nitrous oxide as a substitute for enflurane is less than might be expected when adding up the MAC values.
Röpcke
H
H
Klinik und Poliklinik für Anästhesiologie, Rheinischen Friedrich-Wilhelms-Universität Bonn.
Schwilden
H
H
D000328:Adult; D000769:Anesthesia, Inhalation; D018685:Anesthetics, Inhalation; D004347:Drug Interactions; D004569:Electroencephalography / Q000187:drug effects*; D004737:Enflurane; D005260:Female; D006439:Hemodynamics / Q000187:drug effects / Q000502:physiology; D006801:Humans; D007813:Laparotomy; D009609:Nitrous Oxide; D012129:Respiratory Function Tests
D018685:Anesthetics, Inhalation; D004737:Enflurane; D009609:Nitrous Oxide
Die Interaktion von Stickoxidul und Enfluran bei einem EEG-Median von 2-3 Hz ist additiv, aber schwächer als bei 1,0 MAC.