Desfluran und Isofluran bei Niedrigflussnarkosen: Verbrauch und Kosten bei forcierter Frischgasreduktion

Background. In the present investigation we compared the consumption of desflurane (DES) and isoflurane (ISO) using a standardized minimal flow protocol with a forced reduction of the fresh gas flow (FGF). Methods. 54 adult women were examined. After induction of anaesthesia a forced reduction of the FGF was started: 5 min 0.5 l/ min O 2 + 1 l/min N 2 O, 10 min 0.5 l/min O 2 + 0.5 l/min N 2 O; finally 0.3 l/min O 2 + 0.2 l/min N 2 O up to the end of surgery. The consumption of DES/ISO was determined with a precision balance. Results. In the DES group the uptake was around 0.3 Vol.-%, i.e. less than 8% of the target 2/3-MAC value was taken up. For ISO the uptake was around 0.25 Vol.-%, i.e. approximately 30% of the target 2/3-MAC value. The DES consumption was after 60 min 17.0 ± 1.1g, 120 min 27.3 ± 1.8 g and 180 min 36.5 ± 1.7 g. ISO consumption was significantly lower: 7.6 ± 0.8 g, 12.4 ± 1.7 g and 15.5 ± 1.6 g. The use of DES yielded higher costs, i.e. 2.28 ? for 60 min, 3.63 ? for 120 min and 4.97 ? for 180 min. The consumption of the inhaled anaesthetics can be calculated as: DES (g) = 4.84 + 0.184 x duration (min) (R 2 = 0.981), ISO (g) = 2.049 + 0.0826 x duration (R 2 =0.979). The costs are: DES (?) = 0.85 + 0.0323 x duration (min); ISO (?) = 0.19 + 0.0077 x duration (min). Conclusion. With a forced reduction of the FGF the DES consumption is still higher.