A System Model for Closed-circuit Inhalation Anesthesia II. Clinical Validation

Lerou, J.G.C.; Dirksen, R.; Kolmer, H.H. Beneken; Booiji, Leo H. D. J.; Borm, George F.

doi:10.1097/00000542-199108000-00010

Cited by 16 publications

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“…It incorporated a multicompartment model of the circulation, a two‐compartment lung, but only a one‐compartment breathing system. It was used to match observed data over periods up to 2–3 h derived from intermittent injection of liquid anaesthetic into an almost totally closed breathing system [4–6].…”

mentioning

confidence: 99%

The theoretical ideal fresh‐gas flow sequence at the start of low‐flow anaesthesia

Mapleson

1998

Anaesthesia

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SummaryA spreadsheet model of a circle breathing system and a 70-kg anaesthetised 'standard man' has been used to simulate the first 20 min of low-flow anaesthesia with halothane, enflurane, isoflurane, sevoflurane and desflurane in oxygen. It is shown that, with the fresh-gas flow set initially equal to the total ventilation and the fresh-gas partial pressure to 3 MAC, the end-expired partial pressure can be raised to 1 MAC in 1 min with desflurane and sevoflurane, 1.5 min with isoflurane, 2.5 min with enflurane and 4 min with halothane. Sequences of lower fresh-gas flow and partial pressure settings are given for then maintaining 1 MAC end-expired partial pressure, with a minimum usage of anaesthetic, e.g. 13 ml of liquid desflurane in 20 min (of which only 33% is taken up by the patient) if the minimum acceptable flow is 1 l.min ¹1 , or 8 ml (with 57% in the patient) if the minimum is 250 ml.min ¹1 .

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mentioning

confidence: 99%

The theoretical ideal fresh‐gas flow sequence at the start of low‐flow anaesthesia

Mapleson

1998

Anaesthesia

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“… Drug Simulations: Simulations were performed using published pharmacokinetic and inhalation–opioid interaction models . Sevoflurane levels are presented as effect‐site (not end‐tidal) concentrations.…”

Section: Key Concepts Of Drug Display Monitorsmentioning

confidence: 99%

“…The time window presented starts 50 min into the anaesthetic to 20 min after the anaesthetic is turned off. Isoflurane and fentanyl simulations were performed using published pharmacokinetic and pharmacodynamic models . Definitions, simulated patients’ characteristics, assumptions and limitations are presented below Table .…”

Section: Emergencementioning

confidence: 99%

An introduction to predictive modelling of drug concentration in anaesthesia monitors

DeCou

Johnson

2017

Anaesthesia

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Summary A significant amount of anaesthetists’ work involves the prediction of drug effects and interactions to produce a smooth general anaesthetic that minimises drug side effects and promotes rapid emergence. Successfully managing this process requires a basic understanding of drug effects, experience and inevitably some guesswork, since it is difficult (and in some cases impossible) to anticipate all relevant patient and surgical factors. Although data are generally available to allow calculation of plasma drug and effect site concentrations, this is often difficult to apply in complex clinical contexts, particularly when multiple drug types are used. In recent years, manufacturers have developed and incorporated into anaesthetic workstations technologies that use drug pharmacodynamic and pharmacokinetic data to predict drug effects and interactions. Such systems can predict the duration and effects of drugs during anaesthesia and assist the anaesthetist to understand complex drug interactions. With this information available, different drug types, doses and combinations may be tailored in a scientific way to maximise useful effects whilst minimising overdose and side‐effects, particularly in high‐risk patients. Examples are used to illustrate how such systems can be used in practice, and how drug effects and interactions can be simulated to “rehearse” an anaesthetic before any drugs are actually administered. At present only a small number of anaesthetic workstations use this technology, and as yet they are not able to manage all drugs used in anaesthetic practice. However, such systems have the potential to help anaesthetists manage the complexity of their work, and to provide information on predicted drug effects in a way that is useful and relevant to both experienced anaesthetists and trainees.

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“…As part of earlier work, this model had been extended to include a full range of inhalational agents 6 . The 'Heffernan' model has the particular advantage that it incorporates a circle circuit and does not assume a totally closed circuit with direct injection of liquid agent 7 .…”

Section: Evolution Of the Systemmentioning

confidence: 99%

The Development of a System to Guide Volatile Anaesthetic Administration

Kennedy

2011

Anaesth Intensive Care

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We have developed and deployed within our operating rooms a system which provides real-time estimates of effectsite levels of inhalational anaesthetic agents along with forward predictions of end-tidal and effect-site concentrations. The initial aim of this project was to provide users of inhalational agents with tools similar to those available in target-controlled infusion systems. This paper describes the development and implementation of the system and outlines evaluation and uses of the system. The prototype was developed by combining a locally developed data logging and trend display system with a model of uptake developed as a teaching tool in 1982. This uptake model performs as well as contemporary models of propofol uptake and distribution. Following initial evaluation, the system has been deployed in over half our operating rooms and uses data gathered from the Datex/GE Anaesthesia Delivery Unit anaesthetic machines. We have conducted a number of studies of the system itself, explored aspects of the underlying models, and used the system to investigate effect-site guided anesthesia and as a tool for data collection in other studies. The system has been well accepted locally and has been shown to facilitate faster changes in inhalational levels. We have also seen a significant decrease in fresh gas flow rates over recent years and attribute this in part to the predictive system, which simplifies the task of determining the appropriate combination of gas flow and vapour dial setting. The system also provides a useful platform for a range of research projects.

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A System Model for Closed-circuit Inhalation Anesthesia II. Clinical Validation

Cited by 16 publications

References 0 publications

The theoretical ideal fresh‐gas flow sequence at the start of low‐flow anaesthesia

The theoretical ideal fresh‐gas flow sequence at the start of low‐flow anaesthesia

An introduction to predictive modelling of drug concentration in anaesthesia monitors

The Development of a System to Guide Volatile Anaesthetic Administration

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