• Introduction: Greenhouse gases threaten the health and safety of humanity. The Declaration of Helsinki seeks to protect human health and emphasizes the urgency of implementing sustainable strategies. Sustainability is defined by three pillars: economic (costs), social (clinical effectiveness), and environmental (environmental impact). Clinical effectiveness in cardiac surgery has a new paradigm: "optimized recovery," which translates into fewer complications, earlier extubation, shorter ICU stays, and potential cost reductions. The objective of this study is to compare the sustainability of the optimized recovery anesthetic technique with standard anesthetic practice in coronary artery bypass graft surgery, using a non-randomized interventional study design.
• Methods: Patients aged 18 years or older with coronary artery disease scheduled for elective coronary artery bypass graft surgery will be recruited. Combined procedures and reinterventions will be excluded. Sample size: The optimized recovery group is expected to reduce postoperative mechanical ventilation by two hours. With a 95% confidence interval, 80% power, and a 1:3 ratio between the groups, a sample size of 29 and 87 patients was estimated for the optimized recovery and standard anesthesia groups, respectively.
• The optimized recovery technique includes, preoperatively, oral pregabalin 75 mg, fasting, no benzodiazepines, total intravenous anesthesia, low-dose intravenous fentanyl, methadone 0.1-0.2 mg/kg IV, erector spinae plane block with 0.25% bupivacaine (20 mL per side), and postoperative nausea and vomiting prophylaxis with dexamethasone. Postoperatively, administer paracetamol 1 g IV every 6 hours, NSAIDs, and methadone 1 mg IV as needed. The standard anesthetic technique involves the anesthesiologist administering anesthesia as they have routinely done prior to the study, without changes.
• Four anesthesiologists will participate in the study. Only one anesthesiologist will perform the OR technique, and their results will be compared with those of the other three, who will use their standard anesthetic technique. Patient assignment is independent, based on the hospital's schedule.
• Analysis: The clinical effectiveness of each technique will be evaluated based on ICU extubation time. An economic analysis will be conducted based on average costs, and critical environmental impacts will be estimated through a life-cycle assessment.
• Outcome: The performance of the indicator "Costs in Euros/CO2e/Extubation Time" will be studied. These will contribute to the estimation of an anesthetic strategy that addresses the challenges of sustainable medicine, reduces emissions, and enables the rational use of resources and their associated costs, offering environmentally friendly and clinically effective health solutions.

I• Introduction:

Today, it is clear that protecting human health without ensuring a healthy environment is counterproductive. The 2020 Helsinki Declaration calls for "awareness of the strong interrelationship between human and planetary health". Due to greenhouse gases (GHG), we face the so-called "climate emergency," as climate change threatens the health and security of humanity. However, the healthcare industry is one of the main sources of pollutants and GHG. In the US, the healthcare sector alone is responsible for 9-10% of national GHG emissions and other toxic emissions, amounting to 123,000-381,000 DALYs per year (Disability-Adjusted Life Years). Hospitals account for significant resource consumption and waste and are responsible for almost half of the healthcare sector's GHG emissions. In the healthcare sector, operating rooms account for at least 30% of a hospital's total waste. In a hospital, emissions from anesthetic procedures stand out due to the use of certain drugs and clinical gases, which alone can account for more than 45% of a high-complexity center's CO2e emissions. Therefore, environmental sustainability is becoming a crucial aspect for anesthesiology.

To assess the environmental impact of a clinical practice, a life-cycle assessment (LCA) is necessary. This is an environmental evaluation of products, systems, or services that quantifies the environmental impacts generated throughout their life cycle. CO2e emissions are the most important impact indicator or category due to their role in climate change, harm to human health (expressed in DALY), damage to ecosystems, and resource depletion. Life cycle assessment studies of clinical services include: childbirth procedures, hysterectomy, hemodialysis and peritoneal dialysis, plastic surgery, cataract extraction, laparoscopic procedures, and intensive care.

Within medical and surgical services, myocardial revascularization surgery is one of the procedures that uses the most operating room resources, a space where the highest GHG emissions have been reported, with the greatest resource and energy consumption.

On the other hand, clinical effectiveness in relation to the perioperative period, of myocardial revascularization surgery, has a new paradigm especially for anesthesiology: "enhanced recovery" or "optimized recovery" has has been associated with a decrease in postoperative respiratory complications and a greater likelihood of early extubation, shortening stays in intensive care units and hospitals, which could be reflected in lower costs associated with this type of care.

Sustainability is defined by three pillars: economic, social, and environmental dimensions. Thus, a sustainable anesthetic strategy for coronary heart surgery, compared to other anesthetic techniques, would aim for a reduction in current costs (economic), mitigate its impact by identifying critical points of CO2 emissions (environmental impact), and achieve better clinical effectiveness with an optimized recovery anesthetic strategy in terms of extubation time (social dimension). This is the problem we wish to address: how to make anesthetic practice sustainable by studying an optimized recovery technique in one of the most complex and resource-intensive surgical procedures, myocardial revascularization.

• Methods

General objective:

To establish the relative sustainability of the optimized recovery anesthetic technique with respect to the usual anesthetic practice in myocardial revascularization surgery performed at the Hernán Henríquez Aravena Hospital in Temuco.

Specific objectives:

1. To identify the differences in clinical effectiveness in postoperative recovery, specifically regarding early extubation, between the two anesthetic strategies.
2. To identify the critical points in the life cycle analysis of standard anesthetic practice and the optimized recovery anesthetic strategy in myocardial revascularization surgeries.
3. To understand the cost behavior of standard anesthetic practice and the optimized recovery anesthetic strategy in myocardial revascularization surgeries performed.
4. Estimate the damage to human health, DALYs, generated by the environmental critical points of the life cycles of the usual anesthetic practice and the optimized recovery anesthetic strategy in myocardial revascularization surgeries.

This project will conduct a non-randomized interventional study and implement an optimized anesthetic recovery strategy for coronary artery bypass graft surgery. This study will perform a sustainability analysis of an optimized recovery anesthetic technique compared to a usual anesthetic practice for myocardial revascularization surgery at the Hernán Henríquez Aravena Hospital in Temuco (HHHA).

The anesthetic strategies to be compared are common practice or standard anesthetic practice (SAP) and the proposed optimized recovery (OR) approach.

The sample size calculation is based on the primary variable, the number of hours of mechanical ventilation (extubation time), comparing SAP with the OR approach. The expected mean and standard deviation for SAP were obtained from the cardiovascular ICU's continuous record database for a six-month period in 2023: 4.6 hours and 3.3 hours, respectively. OR is expected to reduce the mean time by 2 hours while maintaining the same recorded variability. For the sample size calculation, a 95% confidence level, 80% statistical power, and a 1:3 ratio, a sample size of 29 patients was estimated for the OR group and 87 for the SAP group, for a total of 116 patients.

Feasibility and Sampling: The hospital performs 500 cardiac surgeries annually, 350 of which are coronary artery bypass grafts. Patients will be selected consecutively. Allocation method: Four anesthesiologists will be included in the study. Only one anesthesiologist will perform the OR technique, and the results will be compared with those of the other three, who will apply their SAP. The selection of the single anesthesiologist who will perform the procedure will be based on convenience. Masking: Anesthesiologists not exposed to the procedure will continue to administer anesthesia using their usual technique, on days other than the day the OR technique is performed, independently of the patients' surgical schedule. The anesthesiologist will be masked for data analysis.

Clinical variables: Patient variables: age, weight, and height. Medical history or concomitant pathology. Anesthesia variables: drugs used, anesthesia duration, resources, and energy used. Surgical variables: number of coronary artery bypass grafts, surgical time, and length of stay in the operating room. ICU variables: extubation time and length of stay in the ICU.

Data Collection: Data and information on supplies will be obtained from the hospital database and directly collected during each procedure, after obtaining informed consent. Only the outcome variable, ICU extubation time, will be recorded outside the system boundaries.

• Proposed Analysis: Clinical Effectiveness Analysis: The clinical effectiveness outcome will be the time to extubation after ICU admission. This will allow a comparison of the clinical effectiveness of the enhanced recovery intervention with standard practice, assuming that ICU management is standardized for both interventions and that proactive measures aimed at early extubation and reduced ICU stay are routine.

Economic Analysis: The cost of the intervention will be updated and described, including marginal, incremental, and average costs. Direct costs will be estimated using micro-costing techniques. Direct healthcare costs associated with the health technologies used, such as medications, medical devices, and care provided by healthcare professionals, among others, will be measured and quantified. The labor cost of each professional participating in the interventions will be quantified by measuring the number of minutes each professional works. The costs of infrastructure use (electricity, water, heating, operating room time, operating room fees) used in each procedure will be determined as follows: Depreciation of equipment and infrastructure will not be included. The cost will have an operational focus.

Environmental Impact Analysis: The life-cycle assessment will be conducted in accordance with the methods established in ISO 14040 (2006a) and ISO 14044 (2006b). These will consider: The scope, which will encompass inputs from "cradle to grave", including those used to perform each anesthetic procedure from the moment the patient enters the operating room until they leave. The functional unit is an adult patient under anesthesia for 1 hour, weighing an average of 70 kg, and the reference flow will be the quantity of anesthetics and other supplies used during a myocardial revascularization surgery. The system boundaries encompass the extraction of raw materials, production, use, and end-of-life of the processes and products required for each type of anesthetic technique, from the moment the patient enters the operating room until they leave. Next, a life cycle inventory analysis will be conducted. Information and costs for each procedure will be obtained from the hospital's electronic records. Real-time data will be obtained on the quantities of medications used and waste generated, and the details of each component will be quantified. The impacts from waste transportation will be calculated based on distances from the hospital to the landfill and recycling facilities. Electricity consumption will be quantified directly in each operating room. An environmental impact study will be conducted using the CCALC database and OpenLCA software to estimate CO2e emissions. Finally, significant environmental flows and aspects (emissions, resources, waste, inputs, etc.) will be identified, along with the life-cycle stage at which they occur and the critical points. The resulting harm to human health, measured in DALYs, will also be estimated.

Sustainability Analysis: After establishing the clinical effectiveness of the intervention in terms of extubation times, the sustainability of each intervention will be evaluated by analyzing updated anesthesia costs for myocardial revascularization surgery and the critical environmental impacts per hour of anesthetized patient in the operating room (functional unit). This will yield an indicator expressed as costs in Euros/critical points of environmental damage (CO2e) per hour of an anesthetized patient in the operating room, using this as the average value of the ratio.

Inclusion Criteria:

1. Patients with coronary artery disease scheduled for coronary artery bypass graft surgery at Dr. Hernán Henríquez Aravena Hospital in Temuco.
2. Competent patients over 18 years of age, meaning they can easily understand the informed consent process and the characteristics of the study.
3. Elective interventions.

Exclusion Criteria:

1. Interventions combined with other procedures or surgeries.
2. Reoperations or second cardiac or thoracic surgical interventions.

Patients with coronary artery disease scheduled for coronary artery bypass graft surgery at Dr. Hernán Henríquez Aravena Hospital in Temuco.

The full database will be accessible in the publication through a provided link.