Ultra-Low-Flow Anesthesia and Carbon Footprint

January 26, 2026 updated by: Ekin Guran, MD, Dr Abdurrahman Yurtaslan Ankara Oncology Training and Research Hospital

The Impact of Ultra-Low-Flow Sevoflurane Anesthesia on Carbon Footprint and Cost: A Randomized Controlled Study in Cardiac Surgery Patients

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.

Study Overview

Status

Completed

Conditions

Intervention / Treatment

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.

Study Type

Interventional

Enrollment (Actual)

92

Phase

  • Not Applicable

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Locations

  • Turkey (Türkiye)
    • Ankara
      • Ankara, Ankara, Turkey (Türkiye), 06810
        • Etlik City Hospital

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

  • Adult
  • Older Adult

Accepts Healthy Volunteers

No

Description

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)

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Treatment
  • Allocation: Randomized
  • Interventional Model: Parallel Assignment
  • Masking: Double

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Active Comparator: 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.
Drug: 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.
Active Comparator: 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
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.

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Time Frame
Total sevoflurane consumption (mL per case), measured at the end of surgery.
Time Frame: throughout the surgery
throughout the surgery

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
carbon footprint
Time Frame: throughout the surgery
Estimated CO₂e emissions (calculated from anesthetic use)
throughout the surgery

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Dr Abdurrahman Yurtaslan Ankara Oncology Training and Research Hospital

Collaborators

Ankara Etlik City Hospital

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

July 30, 2025

Primary Completion (Actual)

September 15, 2025

Study Completion (Actual)

January 15, 2026

Study Registration Dates

First Submitted

December 10, 2025

First Submitted That Met QC Criteria

December 23, 2025

First Posted (Actual)

January 2, 2026

Study Record Updates

Last Update Posted (Actual)

January 27, 2026

Last Update Submitted That Met QC Criteria

January 26, 2026

Last Verified

December 1, 2025

More Information

Terms related to this study

Keywords

Other Study ID Numbers

  • Ultra_low_flow

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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