Authors: Wong C S W et al.
Anesthesiology, March 9, 2026, 10.1097/ALN.0000000000006025
This accepted article examined a practical but often overlooked question in total intravenous anesthesia (TIVA): what fresh gas flow (FGF) is actually optimal when anesthetic delivery is not tied to volatile agent administration? Because TIVA does not depend on inhaled anesthetic concentration, clinicians can adjust FGF mainly to manage oxygen delivery, carbon dioxide absorbent use, equipment function, cost, and environmental impact. The authors sought to identify an “optimal” FGF by balancing institutional economics with environmental consequences.
To answer this, the investigators performed a life-cycle assessment of oxygen and air production as well as carbon dioxide absorbent production and disposal. Environmental burden was measured using global warming potential over 100 years (GWP100). They also incorporated institutional cost data for oxygen, air, and CO2 absorbents. Using these inputs, they modeled annual costs and environmental impact across FGFs from 1 to 10 L/min and FiO2 values from 30% to 60%. They then created a web-based calculator that allows users to enter local variables, including electrical grid emissions factors and disposal practices, to determine the best FGF for their own setting.
In their own institution, where the grid emissions factor was 0.599 kgCO2e/kWh and 36.4% of anesthetics were TIVA cases, raising FGF from 1 to 10 L/min dramatically lowered annual cost, from S$12,948 to S$1,572 at FiO2 30%. This cost reduction was driven largely by reduced use of CO2 absorbent at higher gas flows. However, this economic benefit came with a substantial environmental penalty. Over the same FGF range, annual GWP100 increased almost linearly from 1,939 kgCO2e to 5,910 kgCO2e.
An important practical finding was that the greatest cost savings occurred between 2 and 4 L/min. Beyond that range, additional savings became much smaller, meaning that very high FGFs produced diminishing financial returns while continuing to worsen environmental impact. This is probably the most clinically actionable message for many institutions.
The global modeling showed that the environmentally optimal FGF depends heavily on the local electrical grid emissions factor. In very low-emission settings, higher FGF can actually reduce overall carbon impact because it decreases absorbent use enough to offset the environmental cost of gas production. Specifically, when the grid emissions factor was 0.011 kgCO2e/kWh or lower, higher FGF reduced GWP100. With slightly higher but still relatively clean grids, higher FGF remained environmentally reasonable only up to certain limits. For example, up to 6 L/min was favorable when the grid emissions factor was 0.011 to 0.080, and up to 4 L/min when it was 0.080 to 0.20. In higher-emission settings of 0.200 or more, increasing FGF worsened environmental impact throughout.
The authors therefore argue that there is no universal ideal fresh gas flow during TIVA. Instead, the “best” flow depends on local electricity-related emissions, institutional costs, proportion of TIVA cases, oxygen and air sourcing, and the method of CO2 absorbent disposal. Their calculator is meant to help departments tailor decisions to local priorities, whether cost savings, environmental stewardship, or a balance of both.
Overall, this study is valuable because it reframes fresh gas flow during TIVA as a systems-level decision rather than just a technical setting on the anesthesia machine. It reminds clinicians that higher FGF may save money by reducing absorbent consumption, but in many parts of the world that same strategy may increase the overall carbon footprint. The optimal answer is therefore context specific rather than universal.
What You Should Know
This paper is important because it separates TIVA fresh gas flow decisions from the traditional thinking used with volatile anesthesia.
Higher fresh gas flow during TIVA can reduce CO2 absorbent use and lower cost, but it may also increase environmental harm depending on the local energy grid.
The biggest cost benefit seems to occur between 2 and 4 L/min, after which financial savings begin to level off.
In regions with carbon-intensive electricity, higher fresh gas flows are more likely to worsen total environmental impact.
This article gives anesthesia departments a framework for choosing FGF based on their own local economics and sustainability goals rather than using a one-size-fits-all number.
Key Points
The study modeled cost and environmental impact of TIVA fresh gas flow from 1 to 10 L/min.
Higher fresh gas flow lowered institutional cost by reducing CO2 absorbent consumption.
In the authors’ institution, annual cost fell substantially as FGF increased, but carbon emissions rose markedly.
The relationship between FGF and environmental impact depended strongly on local grid emissions factors.
The largest cost savings occurred between 2 and 4 L/min, with diminishing returns above that range.
There is no single universally optimal FGF during TIVA; the best choice is context specific.
Thank you to Anesthesiology for allowing us to summarize this article.