Model-based administration of inhalation anaesthesia. 4. Applying the system model

Lerou, J.G.C.; Verheijen, R.; Booij, L.H.D.J.

doi:10.1093/bja/88.2.175

Cited by 15 publications

(17 citation statements)

References 10 publications

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“…Because the initial wash-in and high uptake by the patient rapidly alter the concentrations of anesthetic gases in the circle system, the need for frequent vaporizer and rotameter adjustments is thought to be too distracting at a time when the anesthesiologist is preoccupied by other tasks. A simple, clinically easy to apply F D -FGF schedule may therefore encourage anesthesiologists more often to use lower FGF early on during the anesthetic [3,4].…”

Section: Discussionmentioning

confidence: 99%

“…Most authors [5][6][7][8][9] first developed a model that describes mass balances in the circle system (circuit and lung wash-in, uptake by the patient, and kinetics in the circle system) and then prospectively tested their model. Clinical performance of these models varies and is agent-dependent [3,10]. We believe there is no real need to model mass balances to develop clinically useful administration schedules for inhaled agents.…”

Section: Discussionmentioning

confidence: 99%

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Development and performance of a two-step desflurane—O2/N2O fresh gas flow sequence

Hendrickx

Dewulf

Mey

et al. 2008

Journal of Clinical Anesthesia

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Development and performance of a two-step desflurane—O2/N2O fresh gas flow sequence

Hendrickx

Dewulf

Mey

et al. 2008

Journal of Clinical Anesthesia

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“…Modern anesthesia machines and continuous gas analysis should allow anesthesiologists to use these techniques more frequently. However, the perceived need for frequent FGF and vaporizer adjustment according to complex administration schedules impedes the frequent use of this technique [1]. For oxygen/nitrous oxide (O 2 /N 2 O) mixtures in particular, the initial high N 2 O uptake and exponentially decreasing uptake pattern is cumbersome [2].…”

Section: Introductionmentioning

confidence: 99%

The ideal oxygen/nitrous oxide fresh gas flow sequence with the Anesthesia Delivery Unit machine

Hendrickx

Cardinael

Carette

et al. 2007

Journal of Clinical Anesthesia

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“…Simple, easy to remember FGF - F D combinations construed from these models could reduce agent consumption while not distracting the anesthesiologist from other tasks during the induction period of anesthesia [3]. …”

Section: Introductionmentioning

confidence: 99%

Mathematical method to build an empirical model for inhaled anesthetic agent wash-in

et al. 2011

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BackgroundThe wide range of fresh gas flow - vaporizer setting (FGF - FD) combinations used by different anesthesiologists during the wash-in period of inhaled anesthetics indicates that the selection of FGF and FD is based on habit and personal experience. An empirical model could rationalize FGF - FD selection during wash-in.MethodsDuring model derivation, 50 ASA PS I-II patients received desflurane in O2 with an ADU® anesthesia machine with a random combination of a fixed FGF - FD setting. The resulting course of the end-expired desflurane concentration (FA) was modeled with Excel Solver, with patient age, height, and weight as covariates; NONMEM was used to check for parsimony. The resulting equation was solved for FD, and prospectively tested by having the formula calculate FD to be used by the anesthesiologist after randomly selecting a FGF, a target FA (FAt), and a specified time interval (1 - 5 min) after turning on the vaporizer after which FAt had to be reached. The following targets were tested: desflurane FAt 3.5% after 3.5 min (n = 40), 5% after 5 min (n = 37), and 6% after 4.5 min (n = 37).ResultsSolving the equation derived during model development for FD yields FD=-(e(-FGF*-0.23+FGF*0.24)*(e(FGF*-0.23)*FAt*Ht*0.1-e(FGF*-0.23)*FGF*2.55+40.46-e(FGF*-0.23)*40.46+e(FGF*-0.23+Time/-4.08)*40.46-e(Time/-4.08)*40.46))/((-1+e(FGF*0.24))*(-1+e(Time/-4.08))*39.29). Only height (Ht) could be withheld as a significant covariate. Median performance error and median absolute performance error were -2.9 and 7.0% in the 3.5% after 3.5 min group, -3.4 and 11.4% in the 5% after 5 min group, and -16.2 and 16.2% in the 6% after 4.5 min groups, respectively.ConclusionsAn empirical model can be used to predict the FGF - FD combinations that attain a target end-expired anesthetic agent concentration with clinically acceptable accuracy within the first 5 min of the start of administration. The sequences are easily calculated in an Excel file and simple to use (one fixed FGF - FD setting), and will minimize agent consumption and reduce pollution by allowing to determine the lowest possible FGF that can be used. Different anesthesia machines will likely have different equations for different agents.

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Model-based administration of inhalation anaesthesia. 4. Applying the system model

Abstract: The regimen is easily remembered, reliable, and lends itself to alternative strategies, but must be guided by the monitoring of gas and vapour concentrations and haemodynamic variables.

Cited by 15 publications

References 10 publications

Development and performance of a two-step desflurane—O2/N2O fresh gas flow sequence

Development and performance of a two-step desflurane—O2/N2O fresh gas flow sequence

The ideal oxygen/nitrous oxide fresh gas flow sequence with the Anesthesia Delivery Unit machine

Mathematical method to build an empirical model for inhaled anesthetic agent wash-in

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