Rethinking CO2 Absorption in Anaesthesia: AMSORB® Plus
- Published on:
Rethinking CO2 Absorption in Anaesthesia: AMSORB® Plus
- Published on:
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The safe and effective removal of carbon dioxide (CO₂) during anaesthesia is a critical yet often overlooked aspect of patient care. With the increasing adoption of low fresh gas flow techniques in anaesthesia worldwide, the safe and effective performance of CO₂ absorbents has come under greater scrutiny. One solution stands out—AMSORB® Plus, a carbon dioxide absorbent engineered for patient safety, efficiency and effectiveness.
What is AMSORB® Plus?
AMSORB® Plus is a carbon dioxide absorbent with a primary role of absorbing CO₂ exhaled by patients during inhalational anaesthesia, particularly during low fresh gas flow applications. Such applications enable rebreathing of anaesthetic vapours, significantly reducing volatile agent consumption and environmental pollution.
First introduced in 2002, AMSORB® Plus has seen increasing uptake in healthcare institutions across the globe. It is a preferred alternative to soda lime-based absorbents, which contain strong base such as sodium hydroxide and additives such as silica and zeolites that can pose safety concerns when desiccated[1].
Engineered for Clinical Excellence
AMSORB® Plus comprises a formulation of calcium hydroxide, calcium chloride, water, and other minor constituents. These are extruded into hard, porous granules with high absorptive capacity. Following a month-long production cycle, each batch undergoes rigorous testing for bulk density, moisture content, granule size, and CO₂ absorption capacity to ensure quality and consistency.
How It Works
The chemistry behind AMSORB® Plus is straightforward yet powerful. CO₂ reacts with calcium hydroxide to produce calcium carbonate (chalk), heat, and moisture—a classic exothermic reaction. The presence of calcium chloride within the formulation accelerates the reaction, allowing for rapid and efficient CO₂ removal from expiratory gas flow. As the granules become saturated, a violet colour change occurs, triggered by the slight drop in pH and granule dehydration. This provides a clear and reliable visual indicator that the absorbent has been exhausted.
Why Does CO₂ Absorption Matter in Low Flow Anaesthesia?
In low fresh gas flow systems, anaesthetic gas flow is reduced to as little as 0.5 L/min, meaning most of the exhaled gases—including CO₂—are recycled. The absorbent plays a pivotal role in removing CO₂ to prevent rebreathing at levels that could interfere with anaesthesia, surgery and post-operative recovery[2].
As fresh gas flow is reduced, less anaesthetic agent is required to maintain minimum alveolar concentration (MAC), translating to significant cost savings. However, this places increased demand on the absorbent. In fact, more absorbent is consumed in low flow settings than in higher flow ones due to the greater volume of CO₂ being channelled through the absorbent.
Safety First: AMSORB® Plus vs. Soda Lime
A key concern with sodium hydroxide-based absorbents is their potential to degrade volatile anaesthetic agents—notably sevoflurane, desflurane, and isoflurane—into harmful by-products such as carbon monoxide, compound A and methanol, especially when the absorbent becomes dry[3][4]. AMSORB® Plus eliminates this risk, as it contains no strong base chemicals common to other absorbents.
A Safe and Cost Effective Solution
AMSORB® Plus offers a permanent and gradual violet colour change to alert users when the material is spent. Unlike soda lime, which often turns white again after rest periods, potentially misleading clinicians, AMSORB® Plus ensures accurate and irreversible visual feedback.
Economically, while more absorbent is used during low flow anaesthesia, the modest cost increase is vastly outweighed by reduced anaesthetic agent consumption. For example, Cobos 2005, in a study found that around 45% of soda lime discarded still had usable absorption capacity due to early disposal out of safety concerns. With AMSORB® Plus, there’s no need to discard pre-emptively, ensuring efficient resource use and cost control.
AMSORB® Plus is more than just an absorbent—it’s a safety upgrade for modern anaesthetic practice. In settings where patient safety, economic efficiency, and clinical performance are paramount, AMSORB® Plus stands as the absorbent of choice.
If you’d like to learn more about AMSORB® Plus, visit out web page and complete the contact form, our team are happy to help.
Dr. Ciarán Magee
References
1. Eger, E. I., et al. (2002). “Hazards of desiccated carbon dioxide absorbents.” Anesthesia & Analgesia, 95(2), 434-439.
2. Baum, J. A., & Aitkenhead, A. R. (1995). Low-flow anaesthesia. British Journal of Anaesthesia, 75(1), 108–112.
3. Fang, Z., & Eger, E. I. (1995). “Compound A formation from sevoflurane is enhanced by desiccated carbon dioxide absorbents.” Anesthesia & Analgesia, 81(3), 564-568.
4. Woehlck, H. J., et al. (1996). “Carbon monoxide production from volatile anesthetics.” Anesthesiology, 84(3), 527-537.
5. Cobos, A., et al. (2005). “Audit of soda lime usage and potential waste in low-flow anaesthesia practice.” Journal of Clinical Anesthesia, 17(5), 354–358.
