Brief review: Theory and practice of minimal fresh gas flow anesthesia

Brattwall, Metha; Warrén-Stomberg, Margareta; Hesselvik, F.; Jakobsson, Jan

doi:10.1007/s12630-012-9736-2

Cited by 63 publications

(48 citation statements)

References 69 publications

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“…There are several benefits of LFA, including decrease in use of inhalational anaesthetic agents, improvement of body temperature and humidity homeostasis, reduce in environmental pollution, and significant economical advantages [9]. Many studies showed that low-flow techniques provide improvements in the heat and moisture conditions of the anesthetic gases, which let to better impacts on respiratory functions and mucociliary clearance [10].…”

Section: Advantages Of Lfamentioning

confidence: 99%

“…Hence, reducing the gas flow under 1 L/min are not recommended in cases of poorly controlled diabetes, prolonged starvation, chronic alcohol use, heavy smoking, and acute alcohol intoxication. Additionally, septicemia, severe bronchial asthma, and malignant hyperthermia are the other reported contraindications to using low-flow techniques [9]. Accumulation of other exogenous gases such as argon, methane and hydrogen has not a clinical significance.…”

Section: Medium Flow 1-2 L·min-1mentioning

confidence: 99%

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A Reminder to Anesthesiologists: Low-Flow Anesthesia

2016

Ann Clin Anal Med

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Scientific letterAlthough many modern anesthesia machines are suitable for using minimal/low-flow anesthetic techniques and closed-circuit drug delivery methods, high (4-6 L/min) gas flow anesthesia is generally preferred by the majority of the anesthesiologists in routine clinical practice [1]. The aim of this brief report is to indicate the benefits and potential risks of low-flow anesthetic techniques, and to attract the attention of anesthesiologists on this important issue which is not completely clear for most of those. The classification of gas flow rates described by Baker [2] in 1994 has been well accepted by the anesthesia world (Table 1). According to this classification, gas flows less than 1 L/min are defined as low-flow anesthesia (LFA). The term of LFA is generally used to define the inhalation anesthesia techniques that have a re-breathing rate at least 50% and a semi-closed re-breathing system. Although these low-flow anesthetic techniques have been known for a long while, some reasons such as traditional anesthetic habits, little or no training in the use of these techniques during the residency, and concerns on providing a desirable anesthetic depth limited their widely use.The practical aspects of LFA Premedication, pre-oxygenation and induction of anesthesia are performed in accordance with the routine practice. After endotracheal intubation or insertion of a laryngeal mask, patient is connected to re-breathing system. LFA technique can be divided into three phases; initial high-flow, low-flow and recovery. The initial phase lasts 10 to 20 minutes, and characterized a high fresh gas flow of about 4 L/min (for example 1.4 L/min O2 and 3.0 L/min N2O). During this period, sufficient denitrogenation is obtained, the desired anaesthetic gas composition is established within the breathing system, and an essential concentration of anesthetic agents is obtained in order to ensure adequate anesthetic depth. Denitrogenation is to provide the purification of nitrogen in the blood with ventilation of 100% O2 in a high flow. Nitrogen in the lungs is removed by denitrogenation, and thus takes its place to O2. As a result of this event, functional residual capacity and the oxygen reserves increase. Denitrogenation is completed in about 6-8 min with using a fresh gas

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Section: Advantages Of Lfamentioning

confidence: 99%

Section: Medium Flow 1-2 L·min-1mentioning

confidence: 99%

A Reminder to Anesthesiologists: Low-Flow Anesthesia

2016

Ann Clin Anal Med

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“…Meanwhile, the declining cost of medical gases enabled a new generation of open circuit anesthesia machines that abolished CO 2 asphyxiation, and halothane eliminated explosions [82,83] . Then, the November-December 1960 issue of Anesthesiology journal was devoted to a symposium entitled "Carbon Dioxide and Man" that consisted of some 17 authoritative papers that purported to review all pertinent properties of CO 2 [84] .…”

Section: The Waters Techniquementioning

confidence: 99%

Four Forgotten Giants of Anesthesia History

Coleman¹,

Internationals²

2016

JAS

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Introduction Does wisdom perhaps appear on the earth as a raven, which is inspired by the smell of carrion? --Friedrich NietzschePast is prologue. Carbon dioxide confusion has played a pivotal role in the evolution of modern anesthesia. Professional anesthesiology organizations have persistently neglected CO 2 management standards in favor of lesser issues [1][2][3][4] , so that the anesthesiology profession remains mired at the crossroads of revolutionary advance and ongoing self-destruction that can only be understood in historical context. Dr. Ralph Waters founded the profession on the basis of a practical new technique that introduced elective intubation and hyperventilation to abolish CO 2 toxicity disasters, but the harmful habit of hyperventilation has distorted anesthesia beliefs, habits, and practices; derailed research; halted professional advance; discouraged opioid treatment; abolished the therapeutic beneits of CO 2 ; exaggerated morbidity and mortality; and introduced a host of vexing clinical problems. It has indirectly fostered the iction that further improvements in anesthesia safety are impossible, which has undermined reimbursement, emasculated staf privileges, devastated morale, discouraged professional membership A , and rationalized the replacement of anesthesiologists by nurses.Meanwhile, the confusing chemistry, physiology, and pathology of carbon dioxide have yielded their secrets, modern anesthesia machines have eliminated the toxicity problem, modern agents have eliminated explosions, and modern monitoring AbstractThe anesthesiology profession may one day serve as a cautionary tale of how power, politics and privilege can perturb science and progress. Previous anesthesia practitioners possessed a superior understanding of physiology and pharmacology, but overenthusiastic CO 2 supplementation with inadequate monitors and machines caused asphyxiation disasters that were improperly attributed to CO 2 toxicity. Dr. Ralph Waters founded the anesthesiology profession on the basis of a practical new anesthetic technique that introduced elective intubation and hyperventilation to eliminate CO 2 toxicity, but mechanical hyperventilation dangerously depletes CO 2 tissue reserves and exaggerates morbidity and mortality. The beneits of CO 2 supplementation were forgotten, and consequent CO 2 confusion has derailed research, discouraged opioid treatment, damaged patient safety, and disrupted professional progress. Anesthesiologists can no longer claim to provide superior service, and hospital administrators are replacing them with nurses. Professional membership is in decline, and professional survival is in question. Modern machines have eliminated asphyxiation, and modern monitoring enables safe and beneicial hypercarbia that complements opioid treatment and minimizes surgical morbidity and mortality. CO 2 reform promises revolutionary advance but faces formidable opposition. [5] . The restoration of past principles using modern capnography, pulse oximetry, synthetic opioids, and improved inha...

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“…Reducing the amount of anaesthetic agent consumed is of interest not only for reducing cost, but also for reducing environmental burden. The merits of reducing flow must not overrule safety, by maintaining adequate oxygen content in the circle, and avoiding hypoxic gas mixture, inadequate anaesthesia control and too light anaesthesia with risk for awareness ii, iii . Increasing and decreasing the circle system anaesthetic concentration during low and minimal flow anaesthesia calls for knowledge around the technique and kinetics of the anaesthetic gas used.…”

Section: Introductionmentioning

confidence: 99%

Wash-in and wash-out of sevoflurane in a test-lung model: A comparison between Aisys and FLOW-i

2017

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Background: Modern anaesthesia workstations are reassuringly tight and are equipped with effective gas monitoring, thus providing good opportunities for low/minimal flow anaesthesia. A prerequisite for effective low flow anaesthesia is the possibility to rapidly increase and decrease gas concentrations in the circle system, thereby controlling the depth of anaesthesia. Methods: We studied the wash-in and wash-out of sevoflurane in the circle system with fixed fresh gas flow and vaporizer setting. We compared two modern anaesthesia work stations, the Aisys (GE, Madison, WI, USA) and FLOW-i (Maquet, Solna, Sweden) in a test lung model. Results: We found fresh-gas flow to have, as expected, a major influence on wash-in, as well as wash-out of sevoflurane. The wash-in time to reach a stable circle 1 MAC (2.1%) decreased from an average of 547 ± 83 seconds with a constant fresh gas flow of 300 ml/min and vaporizer setting of 8%, to a mean of 38 ± 6 seconds at a fresh gas flow of 4 L/min. There were only minor differences between the two works-stations tested; the Aisys was slightly faster at both 300 and 4 L/min flow. Time to further increase circle end-tidal concentration from 1-1.5 MAC showed likewise significant associations to fresh gas and decreased from 330 ± 24 seconds at 300 ml/min. to less than a minute at constant 4 L/min (17 ± 11 seconds), without anaesthetic machine difference. Wash-out was also fresh gas flow dependent and plateaued at 7.5 L/min. Conclusions: Circle system wash-in and wash-out show clear fresh gas dependency and varies somewhat between the Aisys and Flow-i. The circle saturation, reaching 1 MAC end-tidal or increasing from 1-1.5 MAC can be achieved with both work-stations within 1.5 minutes at a constant fresh gas flow of 2 and 4 L/min. Wash-out plateaued at 7.5 L/min.

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Brief review: Theory and practice of minimal fresh gas flow anesthesia

Cited by 63 publications

References 69 publications

A Reminder to Anesthesiologists: Low-Flow Anesthesia

A Reminder to Anesthesiologists: Low-Flow Anesthesia

Four Forgotten Giants of Anesthesia History

Wash-in and wash-out of sevoflurane in a test-lung model: A comparison between Aisys and FLOW-i

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