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: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.

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.

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

BACKGROUND:Liver transplant centers vary in approach to intraoperative vascular accesses, monitoring of cardiac function and temperature management. Evidence is limited regarding impact of selected modalities on postoperative outcomes. OBJECTIVES:To review the literature and provide expert panel recommendations on optimal intraoperative arterial blood pressure (BP), central venous pressure (CVP), and vascular accesses, monitoring of cardiac function and intraoperative temperature management regarding immediate and short-term outcomes after orthotopic liver transplant (OLT). METHODS:Systematic review following PRISMA guidelines and recommendations using the GRADE approach derived from an international expert panel. Recommendations made for: (1) Vascular accesses, arterial BP and CVP monitoring, (2) cardiac function monitoring, and (3) Intraoperative temperature management (CRD42021239908). RESULTS:Of 2619 articles screened 16 were included. Studies were small, retrospective, and observational. Vascular access studies demonstrated low rates of insertion complications. TEE studies demonstrated low rates of esophageal hemorrhage. One study found lower hospital-LOS and 30-day mortality in patients monitored with both PAC and TEE. Other monitoring studies were heterogenous in design and outcomes. Temperature studies showed increased blood transfusion and ventilation times in hypothermic groups. CONCLUSIONS:Recommendations were made for; routine arterial and CVP monitoring as a minimum standard of practice, consideration of discrepancy between peripheral and central arterial BP in patients with hemodynamic instability and high vasopressor requirements, and routine use of high flow cannulae while monitoring for extravasation and hematoma formation. Availability and expertise in PAC and/or TEE monitoring is strongly recommended particularly in hemodynamic instability, portopulmonary HT and/or cardiac dysfunction. TEE use is recommended as an acceptable risk in patients with treated esophageal varices and is an effective diagnostic tool for emergency cardiovascular collapse. Maintenance of intraoperative normothermia is strongly recommended.

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.

Background: According to the "three-compartment" model of ventilation-perfusion ((V) over dot(A)/(Q) over dot) inequality, increased (V) over dot(A)/(Q) over dot scatter in the lung under general anesthesia is reflectedin increased alveolar deadspace fraction (VDA/VA) customarily measured using end-tidal to arterial (A-a) partial pressure gradients for carbon dioxide. A-a gradients for anesthetic agents such as isoflurane are also significant but have been shown to be inconsistent with those for carbon dioxide under the three-compartment theory. The authors hypothesized that three-compartment VDA/VA calculated using partial pressures of four inhalational agents (VDA/VAG) is different from that calculated using carbon dioxide (VDA/VACO(2)) measurements, but similar to predictions from multicompartment models of physiologically realistic "log-normal" (V) over dot(A)/(Q) over dot distributions. Methods: In an observational study, inspired, end-tidal, arterial, and mixed venous partial pressures of halothane, isoflurane, sevoflurane, or desflurane were measured simultaneously with carbon dioxide in 52 cardiac surgery patients at two centers. VDA/VA was calculated from three-compartment model theory and compared for all gases. Ideal alveolar (PAG) and end-capillary partial pressure (PC'G) of each agent, theoretically identical, were also calculated from end-tidal and arterial partial pressures adjusted for deadspace and venous admixture. Results: Calculated VDA/VAG was larger (mean +/- SD) for halothane ( 0.47 +/- 0.08), isoflurane ( 0.55 +/- 0.09), sevoflurane (0.61 +/- 0.10), and desflurane (0.65 +/- 0.07) than VDA/VACO(2) (0.23 +/- 0.07 overall), increasing with lower blood solubility ( slope [Cis], -0.096 [-0.133 to - 0.059], P < 0.001). There was a significant difference between calculated ideal PAG and PC'G median [interquartile range], Pag 5.1 [3.7, 8.9] versus PC'G 4.0 [ 2.5, 6.2], P = 0.011, for all agents combined. The slope of the relationship to solubility was predicted by the log-normal lung model, but with a lower magnitude relative to calculated VDA/VAG. Conclusions: Alveolar deadspace for anesthetic agents is much larger than for carbon dioxide and related to blood solubility. Unlike the three-compartment model, multicompartment (V) over dot(A)/(Q) over dot scatter models explain this from physiologically realistic gas uptake distributions, but suggest a residual factor other than solubility, potentially diffusion limitation, contributes to deadspace.