BACKGROUND:The absolute and relative effects of lowering fresh gas flows (FGF) on the CO 2 equivalent (CO 2 e) emissions of sevoflurane, carrier gases (O 2 /air) and prepacked CO 2 canister remain poorly quantified. We quantified these factors across a 0.2-4 L/min FGF range during the first hour of anesthesia. METHODS:Data were compiled from 3 studies including 132 ASA I-III patients receiving a constant end-tidal sevoflurane concentration (FETsevo) using manual (n = 50) or target controlled delivery (n = 48) with 0.2 to 4 L/min FGF or during automated closed-circuit delivery (CCA) (n=34). Sevoflurane consumption was normalized to both 1.3 and 2.0% FETsevo, and carrier gas use to an inspired O 2 concentration (F I O 2 ) of 30 and 60%. Prepacked CO 2 absorbent usage was calculated using a previously described model for both 130 and 160 mL/min exhaled CO 2 (VCO 2 ). Published CO 2 e values were used to derive CO 2 e of sevoflurane. RESULTS:Sevoflurane CO 2 e increases linearly with FGF (range 2.4 -18.6 kg CO 2 e), except when a brief wash-in period was used due to low FGF (FGF < 1 L/min). Carrier gas CO 2 e decreases with lower FGF but in a more complex manner, and increases with higher F I O 2 . (range 0.010 - 0.124 kg CO 2 e). Absorbent CO 2 e decreases linearly with FGF (range 0 - 0.070 kg CO 2 e). The CO 2 e of sevoflurane is two orders of magnitude higher than CO 2 e of carrier gas and CO 2 absorbent, which are similar. CONCLUSIONS:When delivering sevoflurane in O 2 /air, the CO 2 e contribution of the carrier gas and CO 2 absorbent is less than 3%, even during CCA. While CO 2 e is only one element of a comprehensive life cycle analysis, the presented CO 2 e data underscore that the key to minimizing the global warming potential of sevoflurane is lowering FGF and decreasing FETsevo.

BACKGROUND:The use of capturing devices may become required for the continued use desflurane. This study tested the percentage of desflurane captured by a charcoal filter (CONTRAfluran; Zeosys GmbH, Germany)-workstation (Aisys; GE Healthcare, USA) combination in vitro . METHODS:Desflurane in oxygen/air was administered via an Aisys workstation into a 2-l test lung that was insufflated with carbon dioxide (160 ml/min). First, to confirm that all vaporized desflurane reached the capturing device, the amount of desflurane collected in a Douglas bag attached to the machine exhaust was compared to the vaporized amount during 15-min runs with the following fresh gas flow and vaporizer setting combinations: 0.3 l/min and 8%, 0.5 l/min and 8%, 1 l/min and 6%, 2 l/min and 6%, 3 l/min and 6%, 4 l/min and 6%, 5 l/min and 6%, and 6 l/min and 6%. Next, to determine the effect of carbon dioxide, the capturing device weight gain was measured with the same fresh gas flow run for longer than 1 h but without desflurane. Finally, the ratio of the capturing device weight gain/vaporizer weight loss (which equals the performance, expressed as a percentage) was determined for the same 15-min runs with the desflurane vaporizer settings described above. All experiments were arbitrarily repeated five times. RESULTS:The amount of vaporized desflurane did not differ from the amount collected in the Douglas bag. When carbon dioxide, oxygen, and air were delivered without desflurane, the capturing device lost a relatively small amount of weight (less than 5 g), especially with fresh gas flow less than or equal to 1 l/min. Finally, performance with 0.3, 0.5 to 2, and 3 to 6 l/min fresh gas flow was 103, 100, and 95 to 93%, respectively. CONCLUSIONS:CONTRAfluran charcoal filter in vitro performance for desflurane in oxygen/air combined with the Aisys workstation ranged from 93 to 103% with fresh gas flow of 0.3 to 6 l/min with vaporizer settings that reflect clinical conditions. Defining the place of charcoal filters in clinical practice requires full life-cycle analysis of both the charcoal and inhaled agent.

BACKGROUND:To capture preventable peri-operative patient harm and guide improvement initiatives, many quality indicators (QIs) have been developed. Several National Anaesthesiologists Societies (NAS) in Europe have implemented quality indicators. To date, the definitions, validity and dissemination of such quality indicators, and their comparability with validated published indicators are unknown. OBJECTIVES:The aim of this study was to identify all quality indicators promoted by NAS in Europe, to assess their characteristics and to compare them with published validated quality indicators. DESIGN:A cross-sectional study with mixed methods analysis. Using a survey questionnaire, representatives of 37 NAS were asked if their society provided quality indicators to their members and, if so, to provide the list, definitions and details of quality indicators. Characteristics of reported quality indicators were analysed. SETTING:The 37 NAS affiliated with the European Society of Anaesthesiology and Intensive Care (ESAIC) at the time. Data collection, translations: March 2018 to February 2020. PARTICIPANTS:Representatives of all 37 NAS completed the survey. MAIN OUTCOME MEASURES:QIs reported by NAS. RESULTS:Only 12 (32%) of the 37 NAS had made a set of quality indicators available to their members. Data collection was mandatory in six (16.2%) of the 37 countries. We identified 163 individual quality indicators, which were most commonly descriptive (60.1%), anaesthesia-specific (50.3%) and related to intra-operative care (21.5%). They often measured structures (41.7%) and aspects of safety (35.6%), appropriateness (20.9%) and prevention (16.6%). Patient-centred care (3.7%) was not well covered. Only 11.7% of QIs corresponded to published validated or well established quality indicator sets. CONCLUSIONS:Few NAS in Europe promoted peri-operative quality indicators. Most of them differed from published sets of validated indicators and were often related to the structural dimension of quality. There is a need to establish a European-wide comprehensive core set of usable and validated quality indicators to monitor the quality of peri-operative care. TRIAL REGISTRATION:No registration.

Background:Carbon dioxide absorbers allow the use of fresh gas flow below minute ventilation (V-E). Models are developed and tested in vitro to quantify their performance with variable carbon dioxide load (VCO2), fresh gas flow, V-E, end-tidal carbon dioxide (ETCO2) fraction, and the type of workstation used. Methods:First principles are used to derive a linear relationship between fresh gas flow and fractional canister usage or FCU0.5 (the reciprocal of the time for the inspiratory carbon dioxide fraction to reach 0.5%). This forms the basis for two basic models in which V-E was measured by spirometry or calculated. These models were extended by multiplying V-E with an empirical workstation factor. To validate the four models, two hypotheses were tested. To test whether the FCU0.5 intercept varied proportionally with VCO2 and was independent of V-E, FCU was measured for 10 canisters tested with a fixed 0.3 l/min fresh gas flow and a range of VCO2 while V-E was either constant or adjusted to maintain ETCO2 fraction. A t test was used to compare the two groups. To confirm whether a change in VCO2 accompanied by a change in V-E to maintain ETCO2 fraction would shift the linear fresh gas flow-FCU0.5 relationship in a parallel manner, 19 canisters were tested with different combinations of VCO2 and fresh gas flow. These measured FCU values were compared to those predicted by the four models using Varvel's performance criteria. Results:With 0.3 l/min fresh gas flow, FCU0.5 was proportional with VCO2 and independent of whether V-E was adjusted to maintain ETCO2 fraction or not (P = 0.962). The hypothesized parallel shift of the fresh gas flow-FCU0.5 relationship was confirmed. Both extended models are good candidate models. Conclusions:The models predict prepacked canister performance in vitro over the range of V-E, fresh gas flow, and VCO2 likely to be encountered in routine clinical practice. In vivo validation is still needed.

Because low flow anesthesia reduces waste of environmentally unfriendly inhaled anesthetics, it is coming in the spotlights – again. Despite a detailed theoretical description, considerable teaching efforts of this simple technique have not succeeded in consistently lowering fresh gas flows (FGF) during manual control1. Worse, even though technology has solved the hurdles of manual delivery and the technology is widely available, we fail to maximally implement it. The delivery of inhaled anesthetics with high FGF prior to securing the airway remains common practice. We fail to consistently adjust MAC to age and poorly titrate opioids to reduce the fraction of the MAC we administer. We fail to incorporate hysteresis which is reflected in the use of excessively high FGF and vaporizer settings during wash-in and in the failure to maintain low FGF prior to emergence (“coasting”). By failing to fully appreciate the quantitative effects of the delivery if inhaled anesthetics we miss the opportunity to reduce waste to the absolute minimum. Belief and myth are strong when the environmental impact of inhaled anesthetics is considered. We need better, detailed life cycle analyses with low flow data before making claims pro/con inhaled/TIVA. We tend to lose sight of perspective, and have to continue to weigh the impact of drug selection on patient care.

In this issue of the Acta Anaesthesiologica Belgica, Chakupurakal et al describe a case series of acute CO 2 overexposure in patients undergoing general anesthesia, caused by CO 2 delivery instead of N 2 O 1 .Because the thread of the fittings between the N 2 O and CO 2 cylinders in Belgium differ by only 0.2 mm, N 2 O and CO 2 cylinders could easily be misconnected.The case series illustrates that despite all existing precautions (reviewed in some detail by the authors) deadly mixtures of odorless, colorless, and tasteless gases can still be delivered to the lungs of our patients.CO 2 can kill.It is used to provide euthanasia in animals 2 .Death is caused by its toxic effects, not necessarily by hypoxic mixtures per se (although hypoxemia may contribute).In humans, low concentrations have little, if any, toxicological effects.At higher concentrations (>5%), hypercapnia and respiratory acidosis ensue.Concentrations above 10% may cause convulsions, coma, and death 3 .CO 2 levels of more than 30% rapidly lead to loss of consciousness within seconds.The effects in humans are illustrated in Table 123456In the reports by Chakupural et al., the dialed gas mixture was 50% O 2 and 50% "N 2 O".The CO 2 concentration at the common gas outlet was 297 mmHg or approximately 40% because CO 2 was delivered via a N 2 O flow meter.While the viscosity of CO 2 and N 2 O are identical at room temperature, the density of CO 2 (1.87 kg/m 3 ) is higher than that of N 2 O (1.977 kg/m 3 ), causing the flow of CO 2 to be lower than dialed.Even so, this was a potentially lethal CO 2 concentration.The only line of defense left between the wrong connection and the patient was, fortunately, a properly functioning multigas analyzer with active alarm and discoloration of the sodalime which rapidly alerted the anesthesiologists to the problem.Swift action prevented patient harm: administering 100% O 2 , increasing fresh gas flows, and confirming delivery of O 2 .But what about other lines of defense for other gases we co-administer with O 2 ?Even when the correct gas cylinder is attached, hypoxic mixtures can form when O 2 /N 2 O and O 2 /air are administered in a circle breathing system.N 2 O is not acutely toxic per se but can kill by becoming part of an inspired hypoxic mixture.This risk is supposed to be minimized not only by gas analysis but also by the obligatory O 2 /N 2 O proportioning device.This device increases the relative proportion of O 2 in the O 2 /N 2 O mixture as the total FGF is lowered.Halas, the system does not work: inspired hypoxic mixtures can still form, especially within the 1 -2 L/min FGF range 7 .The system will fail altogether when a CO 2 cylinder is wrongly attached instead of the N 2 O cylinder because even non-hypoxic CO 2 mixtures can be toxic!End-expired gas analysis with properly set alarm limits remains essential.And what about the plain good air we breath?Air/O 2 mixtures can also cause the formation of inspired hypoxic mixtures when an improper mixture of O 2 /air is delivered into a circle breathing system.In a sense, N 2 is worse than N 2 O. First, we do not measure N 2 concentrations because it is a symmetrical molecule (and thus cannot be measured by infrared gas analysis) and because it has no paramagnetic properties (and thusThe odorless, the colorless, the tasteless and the complacent

Anesthetic agent consumption is often calculated as the product of fresh gas flow (FGF) and vaporizer dial setting (FVAP). Because FVAP of conventional vaporizers is not registered in automated anesthesia records, retrospective agent consumption studies are hampered. The current study examines how FVAP can be retrospectively calculated from the agent’s inspired (FIN) and end-expired concentration (FET), FGF, and minute ventilation (MV). Theoretical analysis of agent mass balances in the circle breathing reveals FVAP = [FIN − (dead space fraction * FIN + (1 − dead space fraction) * FET) * (1 − FGF/MV)]/(1-(1 − FGF/MV)). FIN, FET, FGF and MV are routinely monitored, but dead space fraction is unknown. Dead space fraction for sevoflurane, desflurane, and isoflurane was therefore determined empirically from an unpublished data set of 161 patient containing FVAP, FIN, FET, MV and FGF ranging from 0.25 to 8 L/min delivered via an ADU® (GE, Madison, WI, USA). Dead space fraction for each agent was determined empirically by having Excel’s solver function calculate the value of dead space fraction that minimized the sum of the squared differences between dialed FVAP and predicted FVAP. With dead space fraction known, the model was then prospectively tested for sevoflurane in O2/air using data collected over the course of two weeks with one FLOW-i (Getinge, Solna, Sweden) and one Zeus workstation (Dräger, Lübeck, Germany). Because both workstations use an electronically controlled vaporizer/injector, the dialed FVAP were available to allow the calculation of median performance error (MDPE) and median absolute performance error (MDAPE). MDPE and MDAP are reported as median and interquartiles. The empirical dead space fraction for isoflurane, sevoflurane, and desflurane were 0.59, 0.49, and 0.66, respectively. For prospective testing, a total of 149.4 h of useful data were collected from 78 patient with the Zeus and Flow-i combined, with FGF ranging from 0.18 to 8 L/min. The model predicted dialed FVAP well, with a MDPE of −1 (−11, 6) % and MDAPE of 8 (4, 17) %. FVAP can be retrospectively calculated from FIN, FET, FGF, and MV plus an agent specific dead space fraction factor with a degree of error that we believe suffices for retrospective sevoflurane consumption analyses. Performance with other agents and N2O awaits further validation.

Background Oxygen is one of the most commonly used drugs by anesthesiologists. The World Health Organization (WHO) gave recommendations regarding perioperative oxygen administration, but the practice of oxygen use in anesthesia, critical emergency, and intensive care medicine remains unclear. Methods We conducted an online survey among members of the European Society of Anaesthesiology and Intensive Care (ESAIC). The questionnaire consisted of 46 queries appraising the perioperative period, emergency medicine and in the intensive care, knowledge about current recommendations by the WHO, oxygen toxicity, and devices for supplemental oxygen therapy. Results Seven hundred ninety-eight ESAIC members (2.1% of all ESAIC members) completed the survey. Most respondents were board-certified and worked in hospitals with > 500 beds. The majority affirmed that they do not use specific protocols for oxygen administration. WHO recommendations are unknown to 42% of respondents, known but not followed by 14%, and known and followed by 24% of them. Respondents prefer inspiratory oxygen fraction (FiO 2 ) ≥80% during induction and emergence from anesthesia, but intraoperatively < 60% for maintenance, and higher FiO 2 in patients with diseased than non-diseased lungs. Postoperative oxygen therapy is prescribed more commonly according to peripheral oxygen saturation (SpO 2 ), but shortage of devices still limits monitoring. When monitoring is used, SpO 2 ≤ 95% is often targeted. In critical emergency medicine, oxygen is used frequently in patients aged ≥80 years, or presenting with respiratory distress, chronic obstructive pulmonary disease, myocardial infarction, and stroke. In the intensive care unit, oxygen is mostly targeted at 96%, especially in patients with pulmonary diseases. Conclusions The current practice of perioperative oxygen therapy among respondents does not follow WHO recommendations or current evidence, and access to postoperative monitoring devices impairs the individualization of oxygen therapy. Further research and additional teaching about use of oxygen are necessary.

Purpose: Opioids blunt autonomic nervous system (ANS) responses to noxious stimuli. Nociception monitors analyze the same ANS responses and thus might prove useful to guide opioid dosing. However, concomitantly administered hypnotics also blunt ANS responses and may thus jeopardize the usefulness of nociception monitors to guide intra-operative opioid dosing. We therefore studied the PK (prediction probability) of 3 nociception monitors (NOL index, qNOX and SPI) for the prevailing opioid concentration while maintaining the NSRI (noxious stimulus response index) at a low constant value with a range of opioids and inhaled agent combinations. Methods: In 24 consenting ASA I-II patients undergoing robotic assisted radical prostatectomy, anesthesia was maintained with desflurane in O2/air and remifentanil (target controlled infusion). During the dissection phase, the remifentanil effect site concentration (Ce) in each patient was maintained at 1, 3, or 5 ng/mL for 20 min while the end-expired desflurane concentration (FET) was adjusted to keep the noxious stimulus response index (NSRI) at 5; the sequence in which each patient received each of the three remifentanil Ce was randomized. After stabilization, during each 20 min study period, the following data were collected: NSRI, NOL Index, SPI, qNOX, and FETdes. For each parameter, the prediction probability (PK) for Ce remifentanil was calculated. Results: All patients remained hemodynamically stable. Surgery was finished before the last data collection period in 5 patients with a remifentanil Ce = 5 ng/mL, and in 1 patient with a remifentanil Ce = 1 ng/mL. All other data have been included in the data analysis. The prediction probability (PK) calculated for NOL Index, qNOX and SPI for Ce remifentanil was 0.519, 0.470, and 0.477, respectively. Conclusion: Nociception monitoring becomes useless to titrate opioids when the concomitantly administered hypnotic is adjusted to maintain a low NSRI, presumably because suppression of movement to laryngoscopy also ensures suppression of the sympathetic nervous system response to the noxious stimulus present during intra-abdominal resection of the prostate. Both the hypnotic/opioid ratio and stimulus intensity of the stimulus/response pair need to be considered when attempting to use nociception to guide opioid administration.

Potent inhaled anaesthetics are halogenated hydrocarbons with a large global warming effect. The use of fluorinated hydrocarbons (most are not anaesthetics) are being restricted but volatile anaesthetics have been exempted from legislation, until now: the EU has formulated a proposal to ban or at least severely restrict the use of desflurane starting January 2026. This narrative review addresses the implications of a politics-driven decision – without prior consultation with major stakeholders, such as the European Society of Anaesthesiology and Intensive Care (ESAIC) – on daily anaesthesia practice and reviews the potential scientific arguments that would support stopping the routine use of desflurane in anaesthetic practice. Of note, banning or severely restricting the use of one anaesthetic agent should not distract the user from sensible interventions like reducing fresh gas flows and developing technology to capture and recycle or destroy the wasted potent inhaled anaesthetics that we will continue to use. We call to join efforts to minimise our professional environmental footprint.

Potent inhaled anaesthetics are halogenated hydrocarbons with a large global warming effect. The use of fluorinated hydrocarbons (most are not anaesthetics) are being restricted but volatile anaesthetics have been exempted from legislation, until now: the EU has formulated a proposal to ban or at least severely restrict the use of desflurane starting January 2026. This narrative review addresses the implications of a politics-driven decision - without prior consultation with major stakeholders, such as the European Society of Anaesthesiology and Intensive Care (ESAIC) - on daily anaesthesia practice and reviews the potential scientific arguments that would support stopping the routine use of desflurane in anaesthetic practice. Of note, banning or severely restricting the use of one anaesthetic agent should not distract the user from sensible interventions like reducing fresh gas flows and developing technology to capture and recycle or destroy the wasted potent inhaled anaesthetics that we will continue to use. We call to join efforts to minimise our professional environmental footprint.

Age-adjusted fraction of minimum alveolar concentration derived from end-tidal anesthetic partial pressure measurement remains a useful drug advisory display to help prevent awareness if interpreted with proper understanding of the quantal and probabilistic nature of minimum alveolar concentration, semantics, drug interactions, and hysteresis.

The use of inhaled anesthetics has come under increased scrutiny because of their environmental effects. This has led to a shift where sevoflurane in O2/air has become the predominant gas mixture to maintain anesthesia. To further reduce environmental impact, lower fresh gas flows (FGF) should be used. An accurate model of sevoflurane consumption allows us to assess and quantify the impact of the effects of lowering FGFs. This study therefore tested the accuracy of the Gas Man® model by determining its ability to predict end-expired sevoflurane concentrations (FETsevo) in patients using a protocol spanning a wide range of FGF and vaporizer settings. After IRB approval, 28 ASA I-II patients undergoing a gynecologic or urologic procedure under general endotracheal anesthesia were enrolled. Anesthesia was maintained with sevoflurane in O2/air, delivered via a Zeus or FLOW-i workstation (14 patients each). Every fifteen min, FGF was changed to randomly selected values ranging from 0.2 to 6 L/min while the sevoflurane vaporizer setting was left at the discretion of the anesthesiologist. The FETsevo was collected every min for 1 h. For each patient, a Gas Man® simulation was run using patient weight and the same FGF, vaporizer and minute ventilation settings used during the procedure. For cardiac output, the Gas Man default setting was used (= Brody formula). Gas Man®’s performance was assessed by comparing measured with Gas Man® predicted FETsevo using linear regression and Varvel’s criteria [median performance error (MDPE), median absolute performance error (MDAPE), and divergence]. Additional analysis included separating performance for the wash-in (0–15 min) and maintenance phase (15–60 min). For the FLOW-i, MDPE, MDAPE and divergence were 1

Soda lime-based CO2 absorbents are safe, but not ideal for reasons of ecology, economy, and dust formation. The Memsorb™ is a novel CO2 removal device that uses cardiopulmonary bypass oxygenator technology instead: a sweep gas passes through semipermeable hollow fibers, adding or removing gas from the circle breathing system. We studied the in vitro performance of a prototype Memsorb™ used with a Zeus IE® anesthesia machine when administering sevoflurane and desflurane in O2/air mixtures. The Zeus IE® equipped with Memsorb™ ventilated a 2L breathing bag with a CO2 inflow port in its tip. CO2 kinetics were studied by using different combinations of CO2 inflow (VCO2), Memsorb™ sweep gas flow, and Zeus IE® fresh gas flow (FGF) and ventilator settings. More specifically, it was determined under what circumstances the inspired CO2 concentration (FICO2) could be kept < 0.5%. O2 kinetics were studied by measuring the inspired O2 concentration (FIO2) resulting from different combinations of Memsorb™ sweep gas flow and O2 concentrations, and Zeus IE® FGFs and O2 concentrations. Memsorb™'s sevoflurane and desflurane waste was determined by measuring their injection rates during target-controlled closed-circuit anesthesia (TCCCA), and were compared to historical controls when using a soda lime absorbent (Draegersorb 800+) under identical conditions. With 160 mL/min VCO2 and 5 L/min minute ventilation (MV), lowering the sweep gas flow at any fixed Zeus IE® FGF increased FICO2 in a non-linear manner. Sweep gas flow adjustments kept FICO2 < 0.5% over the entire Zeus IE® FGF range tested with VCO2 up to 280 mL/min; tidal volume and respiratory rate affected the required sweep gas flow. At 10 L/min MV and low FGF (< 1.5 L/min), even a maximum sweep flow of 43 L/min was unable to keep FICO2 ≤ 0.5%. When the O2 concentration in the Zeus IE® FGF and the Memsorb™ sweep gas flow differed, FIO2 drifted towards the sweep gas O2 concentration, and more so as FGF was lowered; this effect was absent once FGF > minute ventilation. During sevoflurane and desflurane TCCCA, the Zeus IE® FGF remained zero while agent usage per % end-expired agent increased with increasing end-expired target agent concentrations and with a higher target FIO2. Agent waste during target-controlled delivery was higher with Memsorb™ than with the soda lime product, with the difference remaining almost constant over the FGF range studied. With a 5 L/min MV, Memsorb™ successfully removes CO2 with inflow rates up to 240 mL/min if an FICO2 of 0.5% is accepted, but at 10 L/min MV and low FGF (< 1.5 L/min), even a maximum sweep flow of 43 L/min was unable to keep FICO2 ≤ 0.5%. To avoid FIO2 deviating substantially from the O2 concentration in the fresh gas, the O2 concentration in the fresh gas and sweep gas should match. Compared to the use of Ca(OH)2 based CO2 absorbent, inhaled agent waste is increased. The device is most likely to find its use integrated in closed loop systems.

Isocapnic hyperventilation (ICHV) is occasionally used to maintain the end-expired CO2 partial pressure (PETCO2) when the inspired CO2 (PICO2) rises. Whether maintaining PETCO2 with ICHV during an increase of the PICO2 also maintains arterial PCO2 (PaCO2) remains poorly documented. 12 ASA PS I–II subjects undergoing a robot-assisted radical prostatectomy (RARP) (n = 11) or cystectomy (n = 1) under general endotracheal anesthesia with sevoflurane in O2/air (40

Even though morbid obesity affects many factors governing uptake, distribution, and elimination (i.e. pharmacokinetics) of inhaled anaesthetics, its overall effects are modest. Obesity-induced pharmacodynamic changes are also small or non-existent: the minimum alveolar concentration (MAC) and MACawake of modern anaesthetics does not differ between lean and morbidly obese patients.