Why should we change to low- or minimal-flow anesthesia?
Reducing the fresh gas flow has several benefits:
Theory and practice of minimal fresh gas flow anesthesia
The review by Brattwall et al. in the Canadian Journal of Anesthesia, outlines the benefits of minimal fresh gas flow anesthesia. It provides practical guidance on safe implementation of low- and minimal-flow anesthesia in routine clinical practice.
What are potential risks of low-flow anesthesia?
Hypoxic mixtures are the greatest risk of using low-flow anesthesia. Reducing fresh gas flow in a rebreathing circle system results in a difference between the delivered O2 concentration(FD) at the common gas outlet and the inspired O2 (FIO2). Consequently, FIO2 becomes lower than the fraction of delivered oxygen (FDO2). This may not always be sufficiently recognized, and if settings are not adjusted, hypoxic mixtures can develop. An active inspired hypoxic guard has been shown to prevent the formation of hypoxic mixtures.
Inadequate depth of anesthesia
During low-flow anesthesia there is a potential risk for inadequate anesthetic gas concentration. An automatic gas control (AGC) system removes the need for continuous manual adjustments of FGF, FIO2 and EtAA. Targeting FIO2 directly will help avoid hypoxia. Targeting EtAA at the desired speed will reduce the risk of under- or overdosing.