The Influence of Two Different CO2 Absorbers on Sevoflurane Consumption During Anaesthesia

Study Overview
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Brief Summary
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Traditional sodalime CO2 absorbers are known to not only react with CO2 but also with sevoflurane. Therewith, a potentially harmful compound (compound A) is formed that can be nephrotoxic. In the United States, the sevoflurane manufacturer therefore recommends keeping the FGF (FGF) at >2.0 L min-1 if a sodalime CO2 absorbent is used. Amsorb Plus® (Datex-Ohmeda Inc., Madison, WI, USA), is a novel type of CO2 absorbent that does not react with sevoflurane. This allows the FGF to be reduced to 0.5 L min-1. This has two important advantages: (i) less fresh sevoflurane is added to the circle system, and (ii) the sevoflurane that is in the system does not react with the CO2 absorber. Sevoflurane is a potent greenhouse gas with a 100 year CO2-equivalents of 120. Measures that can reduce the consumption of volatile anaesthetics could make a significant contribution to reducing the carbon footprint of the operative process. Additionally, Amsorb Plus® canisters seem to have a longer life span than sodalime canisters and do not need to be disposed of via toxic waste stream, but via domestic waste. In this study, we were interested if (i) the use of Amsorb Plus leads to a reduction in sevoflurane usage and therefore contribute to a reduction in the CO2 footprint of general anaesthesia with sevoflurane, (ii) Does the use of Amsorb Plus® lead to a reduction in the amount of (toxic) waste produced by operating theatres? Comparator: a traditional sodalime CO2 absorber (Medisorb™ Multi-Absorber Original, CareFusion, Helsinki, Finland).

Official Title
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The Influence of Two Different CO2 Absorbers on Sevoflurane Consumption During Anaesthesia

Conditions
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Anesthesia

Intervention / Treatment
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* Other: Comparing two CO2 absorbers in the ventilator circuit


Participation Criteria
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Eligibility Criteria
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Inclusion criteria: Adult patient non-pregnant ASA-I to ASA-III undergoing Sevoflurane based general anaesthesia (in a therapeutic concentration of 1.0 MAC) Elective surgery Scheduled operating time >2 hours. Exclusion Criteria: Unable/ unwilling to participate ASA-IV or higher Age < 18 years Known pregnancy Contra-indications for sevoflurane anaesthesia Emergency surgery Scheduled operating time <2 hours.

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 100 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Study group<br>Patients undergoing surgery (>120 min) with the use of sevoflurane based general anaesthesia (in 1.0 MAC concentration). | Other: Comparing two CO2 absorbers in the ventilator circuit<br>* General anaesthesia will be induced with a standardised regimen (propofol 0.8-2.5 mg·kg-1, sufentanil 0.2 - 0.5 µg·kg-1 and rocuronium 0.5 - 1 mg·kg-1). After tracheal intubation, anaesthesia will be maintained with sevoflurane targeted at 1 MAC end tidal concentration (corrected for age using the formula by Mapleson) in 40% O2. Different ventilator settings will be compared for 30 minutes (in randomised order): I. Sodalime, FGF 2.0 L min-1. II. Amsorb Plus®, FGF 2.0 L min-1. III. Soda lime, FGF, 0.5 L min-1. IV. Amsorb Plus®, FGF 0.5 L min-1. FGF=fresh gas flow.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Influence of CO2 filters on Sevoflurane consumption | Comparing Sevoflurane consumption between Amsorb Plus and sodalime CO2 absorbers | 30 minutes per filter | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Influence of fresh gas flow on Sevoflurane consumption | Comparing Sevoflurane consumption between 0.5 and 2.0 liters per minute fresh gas flow | 30 minutes per fresh gas flow setting |