Background and Goal of Study: 
There is long standing and renewed interest in low-flow anaesthesia in clinical practice because of its economic and environmental advantages and the availability of better anaesthesia technology and monitoring devices. The application of low-flow anaesthesia and ultimately metabolic anaesthesia was limited by the long-known fact that the chemicals used to absorb carbon dioxide may react with volatile anaesthetic agents. As the strong alkalis used in carbon dioxide (CO2) absorbers are responsible for the production of both carbon monoxide and toxic compounds, we present a novel CO2 separating membrane technology (memsorb) that does not create the known dilemma in low flow anaesthesia using chemical absorbents. The goal of this presented study is to evaluate a novel next-generation membrane filter regarding its safe and efficient use in an University hospital clinical setting. 

Materials and Methods:
With the approval of our local ethics committee and investigational testing authorization by Health Canada we recruited 200 patients to evaluate the novel memsorb device (n=100) as compared to a control group using Drägersorb 800+ (control, n=100) (ClinicalTrials.gov Identifier: NCT03014336). After obtaining informed consent, patients (ASA I-III) underwent general anaesthesia for surgical treatment. Standard anaesthesia methods were performed to the discretion of the attending anaesthesiologist and demographic and vital parameters were recorded electronically. Where applicable t-test or ANOVA was used.

Results and Discussion: 
This data set describes preliminary results of a subgroup of 179 patients evaluated to date. We investigated gender, weight, height, intraoperative Fe/FiCO2, Sevorane/ Desflurane consumption and FGF. There were no statistical differences between the demographics of the two subgroups. As a major result we could show comparable data regarding the end-tidal CO2 with a median of 5.1% for memsorb and 5.0% for control, stabile over 2h of anaesthesia. Vapor consumption data did not differ significantly between groups. It was not part of this study to evaluate ultralow flow conditions. Anaesthesiologist used fresh gas flows at their discretion (300 – 2,700ml/ min).

Conclusion(s): 
Memsorb could be shown to remove CO2 out of an anaesthesia circuit safely and efficiently without the known limitations of chemical absorbents. A next subset of this study will evaluate the vapor consumption under low-flow conditions. References (optional)


06 / An Innovative Device For CO2 Removal Using Membrane Technology Instead Of Chemical Absorbent In Anesthetic Circuits: Preliminary Clinical Results