Environmental safety: Air pollution while using MIRUS™ for short-term sedation in the ICU

Efficiency of passive activated carbon anaesthetic gas capturing systems during simulated ventilation

BACKGROUND

Interest in passive flow filter systems to remove sevoflurane from anaesthetic machine exhaust have increased recently to mitigate the environmental impact of volatile anaesthetics. These filter systems consist of chemically activated carbon, with limited evidence on their performance characteristics. We hypothesised that their efficiency depends on filter material.

METHODS

Binding capacity was tested for three carbon filter materials (CONTRAfluran®, FlurAbsorb®, and Anaesthetic Agent Filter AAF633). Adsorption efficiency and resistive pressure were determined during simulated ventilation at different stages of filter saturation and fresh gas flow. In addition, sevoflurane concentration in filtered gas was measured at randomly selected anaesthesia workstations.

RESULTS

Sevoflurane concentration in filtered gas exceeded 10 ppm when saturated with 184 ml sevoflurane each for CONTRAfluran and FlurAbsorb and 276 ml for AAF633. During simulated ventilation, sevoflurane concentration >10 ppm passed through CONTRAfluran and AAF633 at fresh gas flow 10 L min-1 only at maximum saturation, but through FlurAbsorb at all stages of saturation. The resistance pressure of all filters was negligible during simulated ventilation, but increased up to 5.2 (0.2) cm H2O during simulated coughing. At two of seven anaesthesia workstations, sevoflurane concentration in filtered exhaust gas was >10 ppm.

CONCLUSIONS

Depending on the filter material and saturation, the likelihood of sevoflurane passing through passive flow carbon filters depends on the filter material and fresh gas flow. Combining the filter systems with anaesthetic gas scavenging systems could protect from pollution of ambient air with sevoflurane.

Guidelines for inhaled sedation in the ICU

INTRODUCTION AND OBJECTIVES

Sedation is used in intensive care units (ICU) to improve comfort and tolerance during mechanical ventilation, invasive interventions, and nursing care. In recent years, the use of inhalation anaesthetics for this purpose has increased. Our objective was to obtain and summarise the best evidence on inhaled sedation in adult patients in the ICU, and use this to help physicians choose the most appropriate approach in terms of the impact of sedation on clinical outcomes and the risk-benefit of the chosen strategy.

METHODOLOGY

Given the overall lack of literature and scientific evidence on various aspects of inhaled sedation in the ICU, we decided to use a Delphi method to achieve consensus among a group of 17 expert panellists. The processes was conducted over a 12-month period between 2022 and 2023, and followed the recommendations of the CREDES guidelines.

RESULTS

The results of the Delphi survey form the basis of these 39 recommendations - 23 with a strong consensus and 15 with a weak consensus.

CONCLUSION

The use of inhaled sedation in the ICU is a reliable and appropriate option in a wide variety of clinical scenarios. However, there are numerous aspects of the technique that require further study.

High anesthetic exposure leads to oxidative damage and gene expression changes in physicians during medical residency: a cohort study

Evaluation of the possible toxic effects of occupational exposure to anesthetics is of great importance, and the literature is limited in assessing the possible association between occupational exposure to anesthetics and oxidative stress and genetic damage. To contribute to the gap of knowledge in relation to cause-effect, this cohort study was the first to monitor exposure assessment and to evaluate oxidative stress, DNA damage, and gene expression (OGG1, NRF2, HO-1, and TP53) in young adult physicians occupationally exposed to the most modern halogenated anesthetics (currently the commonly used inhalational anesthetics worldwide) in addition to nitrous oxide gas during the medical residency period. Therefore, the physicians were evaluated before the beginning of the medical residency (before the exposure to anesthetics-baseline), during (1 1/2 year) and at the end (2 1/2 years) of the medical residency. Anesthetic air monitoring was performed in operating rooms without adequate ventilation/scavenging systems, and biological samples were analyzed for lipid peroxidation, protein carbonyl content, primary and oxidative DNA damage, antioxidant enzymes and plasma antioxidant capacity, and expression of some key genes. The results showed induction of lipid peroxidation, DNA damage, glutathione peroxidase activity, and NRF2 and OGG1 expression up to the end of medical residency. Plasma antioxidant capacity progressively increased throughout medical residency; oxidative DNA damage levels started to increase during medical residency and were higher at the end of residency than at baseline. Protein carbonyls increased during but not at the end of medical residency compared to baseline. The antioxidant enzyme superoxide dismutase activity remained lower than baseline during and at the end of medical residency, and HO-1 (related to antioxidant defense) expression was downregulated at the end of medical residency. Additionally, anesthetic concentrations were above international recommendations. In conclusion, high concentrations of anesthetic in the workplace induce oxidative stress, gene expression modulation, and genotoxicity in physicians during their specialization period.

Inhaled Sedation with Volatile Anesthetics for Mechanically Ventilated Patients in Intensive Care Units: A Narrative Review

Inhaled sedation was recently approved in Europe as an alternative to intravenous sedative drugs for intensive care unit (ICU) sedation. The aim of this narrative review was to summarize the available data from the literature published between 2005 and 2023 in terms of the efficacy, safety, and potential clinical benefits of inhaled sedation for ICU mechanically ventilated patients. The results indicated that inhaled sedation reduces the time to extubation and weaning from mechanical ventilation and reduces opioid and muscle relaxant consumption, thereby possibly enhancing recovery. Several researchers have reported its potential cardio-protective, anti-inflammatory or bronchodilator properties, alongside its minimal metabolism by the liver and kidney. The reflection devices used with inhaled sedation may increase the instrumental dead space volume and could lead to hypercapnia if the ventilator settings are not optimal and the end tidal carbon dioxide is not monitored. The risk of air pollution can be prevented by the adequate scavenging of the expired gases. Minimizing atmospheric pollution can be achieved through the judicious use of the inhalation sedation for selected groups of ICU patients, where the benefits are maximized compared to intravenous sedation. Very rarely, inhaled sedation can induce malignant hyperthermia, which prompts urgent diagnosis and treatment by the ICU staff. Overall, there is growing evidence to support the benefits of inhaled sedation as an alternative for intravenous sedation in ICU mechanically ventilated patients. The indication and management of any side effects should be clearly set and protocolized by each ICU. More randomized controlled trials (RCTs) are still required to investigate whether inhaled sedation should be prioritized over the current practice of intravenous sedation.

Extracorporeal membrane oxygenation and inhaled sedation in coronavirus disease 2019-related acute respiratory distress syndrome

Coronavirus disease 2019 (COVID-19) related acute respiratory distress syndrome (ARDS) is a severe complication of infection with severe acute respiratory syndrome coronavirus 2, and the primary cause of death in the current pandemic. Critically ill patients often undergo extracorporeal membrane oxygenation (ECMO) therapy as the last resort over an extended period. ECMO therapy requires sedation of the patient, which is usually achieved by intravenous administration of sedatives. The shortage of intravenous sedative drugs due to the ongoing pandemic, and attempts to improve treatment outcome for COVID-19 patients, drove the application of inhaled sedation as a promising alternative for sedation during ECMO therapy. Administration of volatile anesthetics requires an appropriate delivery. Commercially available ones are the anesthetic gas reflection systems AnaConDa^® and MIRUS^TM, and each should be combined with a gas scavenging system. In this review, we describe respiratory management in COVID-19 patients and the procedures for inhaled sedation during ECMO therapy of COVID-19 related ARDS. We focus particularly on the technical details of administration of volatile anesthetics. Furthermore, we describe the advantages of inhaled sedation and volatile anesthetics, and we discuss the limitations as well as the requirements for safe application in the clinical setting.

Inhaled Anesthetics: Environmental Role, Occupational Risk, and Clinical Use

Inhaled anesthetics have been in clinical use for over 150 years and are still commonly used in daily practice. The initial view of inhaled anesthetics as indispensable for general anesthesia has evolved during the years and, currently, its general use has even been questioned. Beyond the traditional risks inherent to any drug in use, inhaled anesthetics are exceptionally strong greenhouse gases (GHG) and may pose considerable occupational risks. This emphasizes the importance of evaluating and considering its use in clinical practices. Despite the overwhelming scientific evidence of worsening climate changes, control measures are very slowly implemented. Therefore, it is the responsibility of all society sectors, including the health sector to maximally decrease GHG emissions where possible. Within the field of anesthesia, the potential to reduce GHG emissions can be briefly summarized as follows: Stop or avoid the use of nitrous oxide (N2O) and desflurane, consider the use of total intravenous or local-regional anesthesia, invest in the development of new technologies to minimize volatile anesthetics consumption, scavenging systems, and destruction of waste gas. The improved and sustained awareness of the medical community regarding the climate impact of inhaled anesthetics is mandatory to bring change in the current practice.

Hepatotoxic and neuroendocrine effects in physicians occupationally exposed to most modern halogenated anesthetics and nitrous oxide

The lack of data on hepatic and hormonal markers for occupational exposure to most modern halogenated anesthetics has stimulated our research, which assessed liver enzymes, high-sensitivity C-reactive protein (hs-CRP) and neuroendocrine response. The study investigated 106 physicians who were categorized in an exposed group (primarily exposed to isoflurane and sevoflurane and less to desflurane and nitrous oxide) as well as as a control group. Anesthetic air monitoring was performed, and biological samples were analyzed for the most important liver enzymes, hs-CRP, adrenocorticotrophic hormone, cortisol and prolactin. No biomarkers were significantly different between the groups. Exposed males showed significant increases in cortisol and prolactin compared to unexposed males. However, values were within the reference ranges, and 22 % of exposed males versus 5 % of unexposed males exhibited higher prolactin values above the reference range. This study suggests that occupational exposure to the most commonly used inhalational anesthetics is not associated with hepatotoxicity or neurohormonal changes.

Use of MIRUS™ for MAC-driven application of isoflurane, sevoflurane, and desflurane in postoperative ICU patients: a randomized controlled trial

Background

The MIRUS™ (TIM, Koblenz, Germany) is an electronical gas delivery system, which offers an automated MAC (minimal alveolar concentration)-driven application of isoflurane, sevoflurane, or desflurane, and can be used for sedation in the intensive care unit. We investigated its consumption of volatile anesthetics at 0.5 MAC (primary endpoint) and the corresponding costs. Secondary endpoints were the technical feasibility to reach and control the MAC automatically, the depth of sedation at 0.5 MAC, and awakening times. Mechanically ventilated and sedated patients after major surgery were enrolled. Upon arrival in the intensive care unit, patients obtained intravenous propofol sedation for at least 1 h to collect ventilation and blood gas parameters, before they were switched to inhalational sedation using MIRUS™ with isoflurane, sevoflurane, or desflurane. After a minimum of 2 h, inhalational sedation was stopped, and awakening times were recorded. A multivariate electroencephalogram and the Richmond Agitation Sedation Scale (RASS) were used to assess the depth of sedation. Vital signs, ventilation parameters, gas consumption, MAC, and expiratory gas concentrations were continuously recorded.

Results

Thirty patients obtained inhalational sedation for 18:08 [14:46–21:34] [median 1st–3rd quartiles] hours. The MAC was 0.58 [0.50–0.64], resulting in a Narcotrend Index of 37.1 [30.9–42.4] and a RASS of − 3.0 [− 4.0 to (− 3.0)]. The median gas consumption was significantly lowest for isoflurane ([ml h⁻¹]: isoflurane: 3.97 [3.61–5.70]; sevoflurane: 8.91 [6.32–13.76]; and desflurane: 25.88 [20.38–30.82]; p < 0.001). This corresponds to average costs of 0.39 € h⁻¹ for isoflurane, 2.14 € h⁻¹ for sevoflurane, and 7.54 € h⁻¹ for desflurane. Awakening times (eye opening [min]: isoflurane: 9:48 [4:15–20:18]; sevoflurane: 3:45 [0:30–6:30]; desflurane: 2:00 [1:00–6:30]; p = 0.043) and time to extubation ([min]: isoflurane: 10:10 [8:00–20:30]; sevoflurane: 7:30 [4:37–14:22]; desflurane: 3:00 [3:00–6:00]; p = 0.007) were significantly shortest for desflurane.

Conclusions

A target-controlled, MAC-driven automated application of volatile anesthetics is technically feasible and enables an adequate depth of sedation. Gas consumption was highest for desflurane, which is also the most expensive volatile anesthetic. Although awakening times were shortest, the actual time saving of a few minutes might be negligible for most patients in the intensive care unit. Thus, using desflurane seems not rational from an economic perspective.

Trial registration Clinical Trials Registry (ref.: NCT03860129). Registered 24 September 2018—Retrospectively registered.