The effect of fresh gas flow during induction of anaesthesia on sevoflurane usage: a quality improvement study

Easy-to-implement educational interventions to bring climate-smart actions to daily anesthesiologic practice: a cross-sectional before and after study

BACKGROUND

Anesthesia contributes significantly to a hospital's carbon footprint. Climate-smart actions have the potential to reduce greenhouse gas emissions. Prerequisites for sustainable behavior of providers are knowledge and awareness. We aimed to assess the change in anesthesiologists' climate-friendly behavior before and after educational interventions in three areas that every anesthesiologist can address in their daily clinical routine: 1) energy use; 2) recycling opportunities; 3) consumption of volatile anesthetics.

METHODS

We performed a cross-sectional before-and-after single center sub-study within the multicenter "Provider Education and Evaluation Project" at the Department of Anesthesiology, RWTH Aachen University hospital from May3 2021 to May 1 2022. Educational interventions consisted of stickers, posters and a presentation on climate-smart actions in anesthesiologists' work routine between the first and the second assessment. For each cross-sectional assessment, all central 28 ORs were observed for one week. During the before-and-after comparison we analyzed: 1) energy wasted in unoccupied ORs because of running computers and turned-on lights at 9 p.m.; 2) feasibility of recycling preoperative anesthesia plastic packaging by determining the difference between calculated weight of unseparated preoperative plastic waste in the first assessment and the weight of actual separated waste in the second assessment; 3) fresh gas flow in balanced anesthesia cases in steady state at 9 a.m., and purchased hypnotics converted to bottles/1000 general anesthesia cases in 2018-2022.

RESULTS

We observed a reduction of wasted energy by 44% in unoccupied ORs. Usage of low fresh gas flow settings increased from 55% to 75%. The average of purchased desflurane in 2018-2020 decreased by 72% in 2022. We calculated 10.33 kg of preoperative plastic waste per week but were unable to implement waste separation for infrastructural and logistical reasons.

CONCLUSIONS

We found that environment-friendly working behaviors increased after the implementation of educational interventions. The causality between the interventions and the observed improvements remains to be proven.

Reducing the environmental impact of mask inductions in children: A quality improvement report

BACKGROUND

Inhalational anesthetic agents are potent greenhouse gases with global warming potential that far exceed that of carbon dioxide. Traditionally, pediatric inhalation inductions are achieved with a volatile anesthetic delivered to the patient in oxygen and nitrous oxide at high fresh gas flows. While contemporary volatile anesthetics and anesthesia machines allow for a more environmentally conscious induction, practice has not changed. We aimed to reduce the environmental impact of our inhalation inductions by decreasing the use of nitrous oxide and fresh gas flows.

METHODS

Through a series of four plan-do-study-act cycles, the improvement team used content experts to demonstrate the environmental impact of the current inductions and to provide practical ways to reduce this, by focusing on nitrous oxide use and fresh gas flows, with visual reminders introduced at point of delivery. The primary measures were the percentage of inhalation inductions that used nitrous oxide and the maximum fresh gas flows/kg during the induction period. Statistical process control charts were used to measure improvement over time.

RESULTS

33 285 inhalation inductions were included over a 20-month period. nitrous oxide use decreased from 80% to <20% and maximum fresh gas flows/kg decreased from a rate of 0.53 L/min/kg to 0.38 L/min/kg, an overall reduction of 28%. Reduction in fresh gas flows was greatest in the lightest weight groups. Induction times and behaviors remained unchanged over the duration of this project.

CONCLUSIONS

Our quality improvement group decreased the environmental impact of inhalation inductions and created cultural change within our department to sustain change and foster the pursuit of future environmental efforts.

Comparison of the effects of 5 and 10 L/minute fresh gas flow on emergence from sevoflurane anesthesia: A randomized clinical trial

BACKGROUND

A high fresh gas flow of >5 L/minute is commonly used for emergence from inhalation anesthesia. In addition, a high fresh gas flow may have detrimental effects on climate change. However, no study has determined the optimal fresh gas flow for emergence from inhalation anesthesia. Therefore, we compared the effect of fresh gas flows of 5 L/minute and 10 L/minute on emergence time from sevoflurane anesthesia.

METHODS

Patients who were scheduled for transurethral resection of bladder tumor were randomly assigned to receive fresh gas flows of 5 L/minute (group 5) or 10 L/minute (group 10) during emergence. Emergence time was defined as the time from discontinuation of sevoflurane to tracheal extubation. The primary outcome was the emergence time, and the secondary outcomes were the time to self-movement and the time to eye-opening.

RESULTS

A total of 54 patients were included. In groups 5 and 10, emergence time (12.1 ± 2.9 minutes vs 11.1 ± 2.7 minutes, respectively; P = .232), time to self-movement (9.4 ± 3.8 minutes vs 8.5 ± 4.6 minutes, respectively; P = .435), and time to eye-opening (11.5 ± 3.1 minute vs 10.6 ± 3.0 minutes, respectively; P = .252) were not significantly different.

CONCLUSIONS

Emergence time, time to self-movement, and time to eye opening were not significantly different between fresh gas flow rates of 5 L/minute and 10 L/minute in transurethral resection of bladder tumor, thus suggesting that fresh gas flow of 5 L/minute is sufficient for emergence from sevoflurane anesthesia.

TRIAL REGISTRATION

ClinicalTrials.gov (NCT05376631).

Implementation approaches to improve environmental sustainability in operating theatres: a systematic review

Operating theatres consume large amounts of energy and consumables and produce large amounts of waste. There is an increasing evidence base for reducing the climate impacts of healthcare that could be enacted into routine practice; yet, healthcare-associated emissions increase annually. Implementation science aims to improve the systematic uptake of evidence-based care into practice and could, therefore, assist in addressing the environmental impacts of healthcare. The aim of this systematic search with narrative synthesis was to explore what implementation approaches have been applied to reduce the environmental impact of operating theatre activities, described by implementation phases and methodologies. A search was conducted in EMBASE, PubMed, and CINAHL, limited to English and publication since 2010. In total, 3886 articles were retrieved and 11 were included. All were in the exploratory phase (seven of 11) or initial implementation phase (four of 11), but none were in the installation or full implementation phase. Three studies utilised a recognised implementation theory, model, or framework in the design. Four studies used interprofessional education to influence individuals' behaviour to reduce waste, improve waste segregation, or reduce anaesthetic gases. Of those that utilised behaviour change interventions, all were qualitatively successful in achieving environmental improvement. There was an absence of evidence for sustained effects in the intervention studies and little follow-up from studies that explored barriers to innovation. This review demonstrates a gap between evidence for reducing environmental impacts and uptake of proposed practice changes to deliver low-carbon healthcare. Future research into 'greening' healthcare should use implementation research methods to establish a solid implementation evidence base. SYSTEMATIC REVIEW PROTOCOL: PROSPERO CRD42022342786.

Renal injury from sevoflurane in noncardiac surgery: a retrospective cohort study

BACKGROUND

Sevoflurane is metabolised into Compound A and fluoride that carry a hypothetical risk of nephrotoxicity. However, a clinically significant association between sevoflurane use and acute kidney injury (AKI) in humans has not been established.

METHODS

We retrospectively reviewed 15 552 patients who underwent noncardiac surgery under general anaesthesia using a volatile agent lasting >3 h between July 2016 and May 2019 at a single centre. Patients were divided into a sevoflurane group or no sevoflurane group (desflurane or isoflurane). The primary outcome was incidence of postoperative AKI, which was defined based on the Kidney Disease: Improving Global Outcomes criteria using creatinine concentration within 48 h postoperatively. Propensity score analysis using inverse probability of treatment weighting and propensity score matching was designed to compare outcomes between groups.

RESULTS

Amongst 13 701 included patients, 11 070 (80.8%) received sevoflurane during anaesthesia. The incidence of AKI was 2.3% (257/11 070) and 2.5% (66/2631) in the sevoflurane and no sevoflurane groups, respectvely (P=0.57). After inverse probability of treatment weighting adjustment, sevoflurane anaesthesia was not significantly associated with postoperative AKI (odds ratio [OR] 1.32; 95% confidence interval [CI]: 0.99-1.76; P=0.059). In the matched cohort, the incidence of AKI was 3.1% (81/2626) and 2.4% (62/2626) in the sevoflurane and no sevoflurane groups, respectively, and sevoflurane anaesthesia was not associated with postoperative AKI (OR 1.32; 95% CI: 0.94-1.86; P=0.11).

CONCLUSIONS

Sevoflurane anaesthesia for >3 h was not associated with postoperative renal injury compared with anaesthesia using other volatile agents.

Are high fresh gas flow rates necessary during the wash-in period in low-flow anesthesia?

In low-flow anesthesia (LFA), there is a wash-in period in which usually high fresh gas flow (FGF) rates are used to achieve the required initial concentration of anesthetic agent in the alveoli. The aim of this study was to compare the efficiency, safety and the consumption of desflurane in LFA using constant FGF (1 L/min) and conventional LFA using high FGF (4 L/min) during the wash-in period. Eighty patients, who were scheduled for elective surgery under general anesthesia with endotracheal intubation, were enrolled in the study. Wash-in was accomplished with 1 L/min FGF (50% O2, 50% air) and 18% desflurane in group 1; and by 4 L/min FGF (50% O2, 50% air) and 6% desflurane in group 2. Throughout the surgery, the vaporizer was adjusted to maintain 0.6 to 0.8 minimum alveolar concentration (MAC). The time required to reach 0.7 MAC was shorter in group 1 (160 seconds [135-181] vs 288 seconds [240-500], P < .001). In 6 patients in group 1 and 13 in group 2, vaporizer settings were adjusted to maintain 0.6 to 0.8 MAC (P = .048). Desflurane consumption in the first hour and total desflurane consumption were higher in group 2 (P < .001 and P = .012, respectively). The efficiency of anesthesia in both the first hour and in total was higher in group 1 (P < .001). It is safe, more efficient, and economical to use 1 L/min FGF during the wash-in period in LFA.

Minimal flow anesthesia can be initiated early with the use of higher fresh gas flow to facilitate desflurane "Wash-in"

Background and Aims:

More than 80% of delivered anesthetic gases get wasted at high fresh gas flows as they are vented out unused. Use of minimal flow anesthesia is associated with less waste anesthetic gas emission and environmental pollution. There is no approved or validated technique to initiate minimal flow anesthesia and simultaneously achieve denitrogenation of the breathing circuit. We studied the wash-in characteristics of desflurane, when delivered with 50% nitrous oxide, to reach a target end-tidal concentration at two different gas flow rates.

Material and Methods:

Patients were allocated randomly to two groups of 25 adults each. In Group A, with the vaporizer dial fixed at 4 vol %, after an initial fresh gas flow of 4 L/min was administered to wash-in of desflurane using the closed-circuit, with 50% N₂O in O₂, and in group B, 6 L/min was used. Minimal flow anesthesia, with 0.5 L/min, was initiated in both groups on attaining a target end-tidal desflurane concentration of 3.5 vol %. After initiation of desflurane delivery, the inspired/expired gas concentrations were noted every minute for 15 min.

Results:

In Group A, the target desflurane end-tidal concentration was reached in 499.2 ± 68.6 s±, and in the Group B (P < 0.001), it was reached significantly faster in 314.4 ± 69.89 s. Denitrogenation of the circuit was adequate in both groups.

Conclusion:

Minimal flow anesthesia can be initiated, without any gas-volume deficit, in about 5 min with an initial fresh gas flow rate of 6 L/min and the vaporizer set at 4 vol%.