The effect of fresh gas flow rate and type of anesthesia machine on time to reach target sevoflurane concentration

Shin, Hye Won; Yu, Hae Na; Bae, Go Eun; Huh, Hyub; Park, Ji Yong; Kim, Ji Young

doi:10.1186/s12871-016-0294-y

Cited by 17 publications

(7 citation statements)

References 14 publications

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“…Our results also show that Maplesons mathematical calculations of a theoretical optimal FGF at around 4 l/min were accurate 6 . The result is also in line with what Shin et al found in their study: increasing the FGF from low flow to moderately high flow will decrease the wash-in time 7 . However, our results show that there seem to be no benefits to raising the FGF to levels of 6 l/min and above while performing a wash-in.…”

Section: Discussionsupporting

confidence: 92%

The impact of fresh gas flow on wash-in, wash-out time and gas consumption for sevoflurane and desflurane, comparing two anaesthesia machines, a test-lung study.

2017

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Low-flow anaesthesia is considered beneficial for the patient and the environment, and it is cost reducing due to reduced anaesthetic gas consumption. An initial high-flow to saturate the circle system ( wash-in) is desirable from a clinical point of view. We measured the wash-in and wash-out times (time to saturate and to eliminate the anaesthetic agent, AA), for sevoflurane and desflurane, in a test-lung with fixed 3 MAC vaporizer setting at different fresh gas flow (FGF) and calculated the consumption of AA. We tried to find an optimal flow rate for speed and gas consumption, comparing two anaesthesia machines (AMs): Aisys and Flow-i. Time to reach 1 minimal alveolar concentration (MAC) (wash-in) decreased (p<0.05) at higher flow rates (1 – 2 – 4) but plateaued at 4-4.8 l/min. The consumption of AA was at its lowest around 4-4.8 l/min (optimal flow) for all but the Aisys /desflurane group. Wash-out times decreased as FGF increased, until reaching plateau at FGF of 4-6 l/min. Aisys had generally shorter wash-in times at flow rates < 4 l/min as well as lower consumption of AA. At higher flow rates there were little difference between the AMs. The “optimal FGF” for wash-out, elimination of gas from the test-lung and circle system, plateaued with no increase in speed beyond 6 l/min. A fresh gas flow of 4 l/min. seems “optimal” taking speed to reach a 1 MAC ET and gas consumption into account during wash-in with a fixed 3 MAC vaporizer setting, and increasing fresh gas flow beyond 6 l/min does not seem to confirm major benefit during wash-out.

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Section: Discussionsupporting

confidence: 92%

The impact of fresh gas flow on wash-in, wash-out time and gas consumption for sevoflurane and desflurane, comparing two anaesthesia machines, a test-lung study.

2017

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“…et al performed a wash-in study using a Primus anesthetic machine connected to a test-lung, using a FGF of 0.5, 1, and 3 L•min − 1 and setting the F V S to 6%. The respective mean time to reach a F A S of 4% for each FGF was 1165, 534, and 155 s [13]. The latter 3 studies were, however, all performed in test-lungs such that the uptake of sevoflurane by body tissues was not considered, so the results cannot be generalized to clinical practice.…”

Section: Discussionmentioning

confidence: 99%

1-1-8 one-step sevoflurane wash-in scheme for low-flow anesthesia: simple, rapid, and predictable induction

et al. 2020

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Background: Sevoflurane is suitable for low-flow anesthesia (LFA). LFA needs a wash-in phase. The reported sevoflurane wash-in schemes lack simplicity, target coverage, and applicability. We proposed a one-step 1-1-8 washin scheme for sevoflurane LFA to be used with both N 2 O and Air. The objective of our study was to identify time for achieving each level of alveolar concentration of sevoflurane (F A S) from 1 to 3.5% in both contexts. Methods: We recruited 199 adults requiring general anesthesia with endotracheal intubation and controlled ventilation-102 in group N 2 O and 97 in group Air. After induction and intubation, a wash-in was started using a fresh gas flow of O 2 :N 2 O or O 2 :Air at 1:1 L•min − 1 plus sevoflurane 8%. The ventilation was controlled to maintain end-tidal CO 2 of 30-35 mmHg. Results: The rising patterns of F A S and inspired concentration of sevoflurane (F I S) are similar, running parallel between the groups. The F A S/F I S ratio increased from 0.46 to 0.72 within 260 s in group N 2 O and from 0.42 to 0.69 within 286 s in group Air. The respective time to achieve an F A S of 1, 1.5, 2, 2.5, 3, and 3.5% was 1, 1.5, 2, 3, 3.5, and 4.5 min in group N 2 O and 1, 1.5, 2, 3, 4, and 5 min in group Air. The heart rate and blood pressure of both groups significantly increased initially then gradually decreased as F A S increased. Conclusions: The 1-1-8 wash-in scheme for sevoflurane LFA has many advantages, including simplicity, coverage, swiftness, safety, economy, and that it can be used with both N 2 O and Air.

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“…Finally, Shin and colleagues performed a wash-in 6 study using a Primus anesthetic machine connected to a test-lung, using a FGF of 0.5, 1, and 3 L•min-1 and setting the FVS to 6%. The respective mean times to reach FAS of 4% for each FGF were 1,165, 534, and 155 sec [13]. The latter 3 studies were, however, all performed in test-lungs such that the uptake of sevoflurane by body tissues was not considered.…”

Section: Discussionmentioning

confidence: 99%

1-1-8 one-step sevoflurane-nitrous oxide wash-in scheme for low-flow anesthesia: simple, rapid, and predictable induction

Tribuddharat

Sathitkarnmanee

Vattanasiriporn

et al. 2019

Preprint

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Background Sevoflurane is suitable for low-flow anesthesia (LFA). LFA needs a wash-in phase. The reported sevoflurane wash-in schemes lack simplicity, target coverage, and applicability. We proposed a one-step 1-1-8 wash-in scheme for sevoflurane-nitrous oxide (N2O) LFA. The objective of our study was to identify times to achieve every alveolar concentration of sevoflurane (FAS) from 1% to 3.5%. Methods We recruited 102 adults requiring general anesthesia with endotracheal intubation and controlled ventilation. After induction and intubation, a wash-in was started using a fresh gas flow of oxygen (O2):N2O at 1:1 L·min-1 plus sevoflurane 8%. The ventilation was controlled to maintain end-tidal carbon dioxide (CO2) of 30-35 mmHg. Results The rising patterns of FAS and inspired concentration of sevoflurane (FIS) are similar and parallel. The FAS/FIS ratio increased from 0.46 to 0.72 within 260 sec. The respective times to achieve FAS of 1%, 1.5%, 2%, 2.5%, 3% and 3.5% were 1, 1.5, 2, 3, 3.5, and 4.5 min. The heart rate and blood pressure significantly increased initially then gradually decreased as FAS increased. Conclusions The 1-1-8 wash-in scheme for sevoflurane has many advantages, including simplicity, coverage, swiftness, safety, and economy. A respective FAS of 1%, 1.5%, 2%, 2.5%, 3%, and 3.5% can be expected at 1, 1.5, 2, 3, 3.5, and 4.5 min. This scheme may be applied for LFA in the situation where anesthetic gas analyzer is not available.

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The effect of fresh gas flow rate and type of anesthesia machine on time to reach target sevoflurane concentration

Cited by 17 publications

References 14 publications

The impact of fresh gas flow on wash-in, wash-out time and gas consumption for sevoflurane and desflurane, comparing two anaesthesia machines, a test-lung study.

The impact of fresh gas flow on wash-in, wash-out time and gas consumption for sevoflurane and desflurane, comparing two anaesthesia machines, a test-lung study.

1-1-8 one-step sevoflurane wash-in scheme for low-flow anesthesia: simple, rapid, and predictable induction

1-1-8 one-step sevoflurane-nitrous oxide wash-in scheme for low-flow anesthesia: simple, rapid, and predictable induction

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