Isoflurane, Sevoflurane and Desflurane consumption in an anaesthetic gas reflector
system with target controlled administration (MIRUS™) versus a semi-closed circle
system with automatic end tidal concentration control (Aisys Carestation™) using
an artificial lung model
Iustin Georgevici, Livia Procopiuc, Dominik Drees, Vladimir Vinnikov, Jennifer Herzog-
Niescery, Philipp Gude, Thomas Peter Weber, Martin Bellgardt
Department for Anaesthesiology and Intensive Care, St. Josefs Hospital – Bochum
University Clinic, Bochum, Germany
Background and Goal of Study: The use of volatile anaesthetics as sedatives in the ICU
is relevant for the patient’s outcome (1). The MIRUS™ System (MS) (Pall Medical,
Dreieich, Germany) is the first anaesthetic gas reflector system which can administer
Desflurane (DES) besides Isoflurane (ISO) and Sevoflurane (SEVO). The MS is able to
independently measure and control anaesthetic gas concentrations. We aimed to compare
the MS anaesthetic gas consumption with the minimal, low and high flow consumption of a
conventional semi-closed anaesthesia machine - the Aisys CS (GE Healthcare, Madison,
WI, USA) which has a similar end tidal concentration control.
Materials and Methods: We assembled an artificial lung model of 2x2L volume with an
additional reservoir of 3.9 L simulating the functional residual capacity. This was connected
to an MS and a Puritan Bennett™ 840 (Covidien, Mansfield, MA, USA) ventilator or an
Aisys CS anaesthesia machine. Measurements were each made continously for 30
minutes after achieving steady state at end tidal concentrations of 0.5, 1.0, 1.5 and 2.5 Vol
% for ISO and SEVO respectively and at 1, 2, 3, 4, 5 and 6 Vol% for DES. The breathing
parameters were held constant (MV 5L/min, RR 10/min, TV 0.5 L). For the Aisys group
measurements for all end tidal concentrations were performed at 4 different fresh gas
flows (FGF): 0.5, 1.0, 2.5 and 5 L/min respectively. The groups were compared using the
Mann Whitney U test (SPSS® v. 24.0).
Results and Discussion: In the clinically relevant domains for ICU sedation (0.5 MAC)
we could derive the following consumptions: MS ISO at 0.5 Vol% consumes an average of
2 mL/h which is identical to the Aisys at FGF 1 L/min; MS SEVO at 1 Vol% consumes an
average of 10 mL/h which is comparable to the Aisys at FGF 2.5 L/min (8.2 mL/h); MS
DES at 3 Vol% uses up an average of 12 mL/h corresponding to the Aisys at FGF 1 L/min
(9.7 mL/h). The MS interpolation curve for all three gases shows a divergent tendence at 3
Vol% which most likely corresponds to the spill over effect described for Desflurane (2).
Conclusions: MS is effective in reducing overdosing with a satisfactory performance of
the reflector system for the clinically interesting concentrations, where the consumption
corresponds to that of a conventional anaesthesia machine at a FGF between 1 (ISO,
DES) and 2.5 L/min (SEVO).
References: 1. Bellgardt M et al, 2016, Eur J Anaesthesiol 33(1):6-13
2. Bomberg H et al, 2014, Anaesthesia 69(11):1241-50.

Isoflurane, Sevoflurane and Desflurane consumption in an anaesthetic gas reflector system with target controlled administration (MIRUS™) versus a semi-closed circle system with automatic end tidal concentration control (Aisys Carestation™) using an artificial lung model