Ultra-Low-Flow Anesthesia and Carbon Footprint

NCT ID: NCT07313969

Last Updated: 2026-01-27

Basic Information

• Recruitment Status: COMPLETED
• Clinical Phase: NA
• Total Enrollment: 92 participants
• Study Classification: INTERVENTIONAL
• Study Start Date: 2025-07-30
• Study Completion Date: 2026-01-15

Brief Summary

This is a prospective, randomized controlled clinical trial evaluating the effects of ultra-low fresh gas flow (0.5 L/min) versus normal fresh gas flow (2.0 L/min) sevoflurane anesthesia in adult patients undergoing on-pump cardiac surgery. The study aims to determine whether ultra-low-flow anesthesia can be used safely to reduce volatile anesthetic consumption and environmental emissions without compromising hemodynamic stability or anesthetic depth.

Eligible adult patients scheduled for elective coronary artery bypass grafting (CABG) or valve surgery under general anesthesia will be randomized in a 1:1 ratio to one of two groups: ultra-low-flow (0.5 L/min) or normal-flow (2.0 L/min). All other anesthetic techniques, including induction drugs, ventilation parameters, temperature management, and perfusion strategies, will be standardized.

The primary outcome is the total amount of sevoflurane consumed per case. Secondary outcomes include intraoperative hemodynamic parameters (heart rate, mean arterial pressure), depth of anesthesia (BIS/MAC values), postoperative recovery times, and estimated carbon dioxide equivalent (CO₂e) emissions.

Outcome assessors and data analysts will remain blinded to group allocation. The findings of this study are expected to provide new evidence regarding the safety, efficiency, and environmental benefits of ultra-low-flow anesthesia techniques in cardiac surgery.

Detailed Description

This randomized controlled trial investigates the impact of ultra-low-flow (0.5 L/min) versus normal-flow (2.0 L/min) sevoflurane anesthesia on anesthetic consumption, intraoperative hemodynamics, and environmental footprint during on-pump cardiac surgery. Although low-flow anesthesia is known to reduce anesthetic agent use and greenhouse gas emissions, evidence regarding its safety and efficiency during cardiopulmonary bypass procedures remains limited.

Adult patients scheduled for elective CABG or valve surgery will be randomly assigned to either an ultra-low-flow or normal-flow group. Randomization will be performed using a computer-generated sequence with variable block sizes and allocation concealment via sequentially numbered, opaque, sealed envelopes. All participants will receive standardized induction, perfusion, and maintenance techniques according to institutional cardiac anesthesia protocols.

The primary outcome measure is total sevoflurane consumption per patient, assessed through vaporizer readings and anesthetic gas analyzer data. Secondary outcomes include intraoperative mean arterial pressure, heart rate, BIS/MAC values, body temperature, recovery characteristics, and calculated CO₂ equivalent emissions. Outcome assessors and data analysts will remain blinded to group allocation.

This study is designed to evaluate both clinical and ecological aspects of anesthetic practice. It aims to determine whether ultra-low-flow anesthesia can provide equivalent anesthetic quality while offering substantial reductions in agent consumption and environmental impact. The findings may contribute to establishing safer and more sustainable anesthesia standards for cardiac surgery.

Conditions

Low Flow Anesthesia; Sevoflurane Anesthesia; Cardiac Surgery

Study Design

• Allocation Method: RANDOMIZED
• Intervention Model: PARALLEL
• Primary Study Purpose: TREATMENT
• Blinding Strategy: DOUBLE

Study Groups

Ultra-Low-Flow Group (0.5 L/min)

Sevoflurane anesthesia with fresh gas flow maintained at 0.5 L/min throughout the maintenance period. A 2 lt/min fresh gas flow will be used in the preoxygenation and intubation phase.

General anesthesia will be maintained with sevoflurane at a fresh gas flow rate of 0.5 L/min using an oxygen and air mixture. The flow rate will be kept constant from post-induction stabilization until the end of the surgery. Ventilation will be paused during cardiopulmonary bypass.

Group Type: ACTIVE_COMPARATOR

ultra low flow anesthesia

Intervention Type: DRUG

General anesthesia will be maintained with sevoflurane at a fresh gas flow rate of 0.5 L/min using oxygen and air mixture. The flow rate will be kept constant from post-induction stabilization until the end of cardiopulmonary bypass.

Normal-Flow Group (2.0 L/min)

Sevoflurane anesthesia with fresh gas flow maintained at 2.0 L/min throughout maintenance period. The flow rate will be kept constant from post-induction stabilization until the end of surgery. Ventilation will be paused during cardiopulmonary bypass

Group Type: ACTIVE_COMPARATOR

normal flow anesthesia

Intervention Type: DRUG

General anesthesia will be maintained with sevoflurane at a fresh gas flow rate of 2.0 L/min using oxygen and air mixture. The flow rate will be kept constant from post-induction stabilization until the end of cardiopulmonary bypass.

Interventions

ultra low flow anesthesia

General anesthesia will be maintained with sevoflurane at a fresh gas flow rate of 0.5 L/min using oxygen and air mixture. The flow rate will be kept constant from post-induction stabilization until the end of cardiopulmonary bypass.

Intervention Type: DRUG

normal flow anesthesia

General anesthesia will be maintained with sevoflurane at a fresh gas flow rate of 2.0 L/min using oxygen and air mixture. The flow rate will be kept constant from post-induction stabilization until the end of cardiopulmonary bypass.

Intervention Type: DRUG

Eligibility Criteria

Inclusion Criteria

• Adult patients aged 18-80 years
• Scheduled for elective on-pump CABG or valve surgery
• ASA physical status II-III
• Written informed consent obtained

Exclusion Criteria

• Emergency surgery
• Severe hepatic or renal dysfunction
• Known allergy to volatile anesthetics
• Significant pulmonary disease (e.g., COPD with GOLD III-IV)

• Minimum Eligible Age: 18 Years
• Maximum Eligible Age: 80 Years
• Eligible Sex: ALL
• Accepts Healthy Volunteers: No

Sponsors

Ankara Etlik City Hospital

OTHER_GOV

Sponsor Role: collaborator

Dr Abdurrahman Yurtaslan Ankara Oncology Training and Research Hospital

OTHER

Sponsor Role: lead

Responsible Party

Ekin Guran, MD

consultant anesthesiologist

Responsibility Role: PRINCIPAL_INVESTIGATOR

Locations

Etlik City Hospital

Ankara, Ankara, Turkey (Türkiye)

Countries

Turkey (Türkiye)

References

McGain F, Sheridan N, Wickramarachchi K, Yates S, Chan B, McAlister S. Carbon Footprint of General, Regional, and Combined Anesthesia for Total Knee Replacements. Anesthesiology. 2021 Dec 1;135(6):976-991. doi: 10.1097/ALN.0000000000003967.

Reference Type: BACKGROUND

PMID: 34529033 (View on PubMed)

Other Identifiers

Ultra_low_flow

Identifier Type: -

Identifier Source: org_study_id