Low Flow AnesthesiaNCT07534839
Low-Flow Anesthesia Without Wash-in: Effects on Oxygenation and Depth of Anesthesia
A study testing Initiation of low-flow anesthesia without wash-in following intubation in people with Low Flow Anesthesia, run by Erzincan Binali Yildirim Universitesi at 1 site in Turkey (Türkiye).
Trial summary
This study aims to evaluate whether adjusting the fresh gas flow rate to low-flow immediately after intubation, without performing a wash-in, is a reliable approach with respect to depth of anesthesia and oxygenation. Read more about this study
- Who is it for?
- Ages 18 to 65 yearsHealthy volunteers can take part
- Conditions the study is for
- Low Flow Anesthesia
- What is being tested?
- Initiation of low-flow anesthesia without wash-in following intubation
- Type of treatment
- Medical device
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 60 participants
- Where
- 1 siteTurkey (Türkiye)
- Study dates
- 1 Mar 2026to 1 Aug 2026
- Phase
- Interventional
- Are there results?
- Not yet: the study is under way
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 18 to 65 years
- All sexes
- Healthy volunteers accepted
- Adult, Older adult
Who may be able to join
- ASA physical status I-II
- Cases lasting longer than 30 minutes
- Non-laparoscopic surgical procedures
Who cannot join
- Patients with life-threatening renal, cardiac, or hepatic disease
- Patients with chronic pulmonary diseases such as asthma or COPD
- Patients with intraoperative hemodynamic instability
- Patients with a body mass index (BMI) lower than 20 or higher than 30
Trial locations and contacts
1 site in 1 country.
Turkey (Türkiye)1 site
Binali Yildirim Univercity
Erzincan, Erzincan, 24000
About this study
Official title: Evaluation of the Safety of Low-Flow Anesthesia Initiated Without Wash-in in Terms of Oxygenation and Depth of Anesthesia Using Arterial Blood Gas Analysis and EEG-Based PSI Monitoring
This study aims to evaluate whether adjusting the fresh gas flow rate to low-flow immediately after intubation, without performing a wash-in, is a reliable approach with respect to depth of anesthesia and oxygenation.
Read the detailed description
Low-flow anesthesia is defined as the delivery of fresh gas flow at a rate of 0.5-1 L/min on the anesthesia machine . Due to its advantages such as reducing costs, decreasing environmental pollution related to anesthetic gases, preserving mucociliary activity, softening secretions, and reducing heat loss, it has attracted considerable attention from anesthesiologists in recent years. However, the main concerns involve maintaining adequate ventilation, ensuring sufficient tissue oxygen delivery, and achieving adequate depth of anesthesia. Therefore, additional monitoring is required for the safe application of low-flow techniques. Exhaled gas volume, airway pressure, fraction of inspired oxygen (FiO₂), volatile anesthetic agent concentration, carbon dioxide concentration, and peripheral oxygen saturation (SpO₂) should be closely monitored. Arterial blood gas sampling is the gold standard for monitoring oxygenation. The Patient State Index (PSI) is a processed EEG index derived from frontal EEG signals that numerically expresses the level of anesthesia/sedation on a scale from 0 to 100. PSI is generated based on spectral and coherence analyses of data obtained from four-channel EEG monitors such as Masimo SedLine®, using advanced artifact filtering, and was developed for objective monitoring of the level of consciousness during general anesthesia. PSI values between 25 and 50 generally indicate an adequate depth of anesthesia, whereas higher values suggest a reduction in anesthetic depth.
In low-flow anesthesia, after induction the patient is connected to mechanical ventilation, and the volatile agent is adjusted to 1 MAC with 50% O₂. Subsequently, wash-in is achieved by administering fresh gas flow at 4-6 L/min for approximately 10 minutes, after which the flow is reduced. However, some studies have reported that initiating anesthesia maintenance directly with low fresh gas flow, without performing wash-in, may also be a feasible approach.
To date, no study has evaluated the reliability of initiating low fresh gas flow during mechanical ventilation without performing wash-in, using arterial blood gas analysis and PSI monitoring. This study aimed to compare the reliability of techniques involving reduction of fresh gas flow using the traditional wash-in method versus without wash-in, in terms of hypoxia and depth of anesthesia, using serial arterial blood gas measurements and PSI monitoring.
- Conditions
- Low Flow Anesthesia
- Being tested
- Initiation of low-flow anesthesia without wash-in following intubation
- Keywords
- general anesthesia, green anesthesia, low flow anesthesia
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
Initiation of low-flow anesthesia without wash-in following intubationDevice
After endotracheal intubation, fresh gas flow is set to 0.75 L/min with 60% O₂. The sevoflurane vaporizer is initially set to 8%, and the sevoflurane concentration is subsequently titrated according to the target MAC value. Anesthesia depth and oxygenation are monitored using PSI monitoring and serial arterial blood gas measurements.
| Study group | Role | What they receive |
|---|---|---|
| Group WI | No intervention | In this group, after intubation, patients were ventilated for 10 minutes with 4 L/min fresh gas flow consisting of 2% sevoflurane and 60% O₂, after which the fresh gas flow rate was reduced to 0.75 L/min |
| Group WO | Active comparator | In this group, after intubation, the fresh gas flow rate was set to 0.75 L/min with 60% O₂. The sevoflurane vaporizer was initially set to 8%, and the sevoflurane concentration was subsequently reduced according to the MAC value Receives: Device: Initiation of low-flow anesthesia without wash-in following intubation |
What is being measured
The primary outcome is the main question the study is designed to answer.
Comparison of arterial oxygen partial pressure (PaO₂) values between groups
Comparison of arterial oxygen partial pressure (PaO₂) and Patient State Index (PSI) values between groups.
Measured: Measured at 10, 20, 30, and 45 minutes after induction of anesthesia and before the end of surgery.
Comparison of Patient State Index (PSI) values between groups.
PSI is an EEG-based index ranging from 0 to 100. Lower values indicate deeper anesthesia; the target range is 25-50 during general anesthesia.
Measured: Continuously monitored intraoperatively and recorded at 10, 20, 30, and 45 minutes after induction of anesthesia.
Secondary outcomes (3)
Mean alveolar concentration (MAC) values
Comparison of MAC values between groups during anesthesia maintenance.
Measured: Continuously monitored intraoperatively and recorded at 10, 20, 30, and 45 minutes after induction of anesthesia.
Total sevoflurane consumption
Comparison of total sevoflurane consumption between groups.
Measured: From induction of anesthesia until the end of surgery (average duration approximately X minutes).
Time to reach target MAC level
Time required to achieve target MAC level after intubation
Measured: Time (minutes) from completion of endotracheal intubation to achievement of MAC 1.0, as measured on the anesthesia monitor
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted16 Apr 2026
- Study start1 Mar 2026
- Primary completion1 Jul 2026 (estimated)
- Study completion1 Aug 2026 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Publications (7)Papers the sponsor has linked to this study.
- Other trials for Low Flow AnesthesiaStudies of the same condition, open and under way.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase N/A
- Primary purpose
- Other
- Allocation
- Randomised
- Intervention model
- Crossover
- Masking
- None (open label)
- Enrolment
- 60 participants (estimated)
Sponsor and investigators
- Lead sponsor
- Erzincan Binali Yildirim Universitesi
- Sponsor type
- University, hospital or other
- Responsible party
- Principal investigator, Fazıl Ahmet Akbulut, MD, Erzincan Binali Yildirim University Mengucek Gazi Training and Research Hospital
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT07534839
- Sponsor's protocol ID
- ErzincanBinaliYildirim
- Status last verified
- Apr 2026
- First submitted
- 29 Mar 2026
- Last updated
- 16 Apr 2026
- Results posted
- No
- Data monitoring committee
- Yes
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- Yes: PO2, PCO2, PSI, Sevoflurane consumption, Demographic data
Publications
Simsek T, Derman S, Kordi RGM, Saracoglu A, Saracoglu KT. The effect of different flow levels and concentrations of sevoflurane during the wash-in phase on volatile agent consumption: a randomized controlled trial. J Clin Monit Comput. 2022 Oct;36(5):1257-1262. doi: 10.1007/s10877-022-00846-w. Epub 2022 Apr 19.
PubMed 35438367Bahar S, Arslan M, Urfalioglu A, Gisi G, Oksuz G, Bilal B, Oksuz H, Doganer A. Low-flow anaesthesia with a fixed fresh gas flow rate. J Clin Monit Comput. 2019 Feb;33(1):115-121. doi: 10.1007/s10877-018-0135-2. Epub 2018 Mar 23.
PubMed 29572589Amirfarzan H, Cassidy KJ, Moaddab M, Demin M, Schumann R, Lewis B. Assessment of seizure duration and utility of using SedLine(R) EEG tracing in veterans undergoing electroconvulsive therapy: a retrospective analysis. J Anesth Analg Crit Care. 2024 Feb 6;4(1):8. doi: 10.1186/s44158-024-00143-9.
PubMed 38321515McIlroy DR, Shotwell MS, Lopez MG, Vaughn MT, Olsen JS, Hennessy C, Wanderer JP, Semler MS, Rice TW, Kheterpal S, Billings FT 4th; Multicenter Perioperative Outcomes Group. Oxygen administration during surgery and postoperative organ injury: observational cohort study. BMJ. 2022 Nov 30;379:e070941. doi: 10.1136/bmj-2022-070941.
PubMed 36450405Dastan R, Kefeli Celik H, Doganay Z. High, Low, and Minimal Flow Anaesthesia Management: Effects on Oxygen Reserve Index and Arterial Partial Oxygen Pressure. J Coll Physicians Surg Pak. 2023 Nov;33(11):1223-1228. doi: 10.29271/jcpsp.2023.11.1223.
PubMed 37926871Varughese S, Ahmed R. Environmental and Occupational Considerations of Anesthesia: A Narrative Review and Update. Anesth Analg. 2021 Oct 1;133(4):826-835. doi: 10.1213/ANE.0000000000005504.
PubMed 33857027Kutlusoy S, Koca E, Aydin A. Reliability of low-flow anesthesia procedures in patients undergoing laparoscopic cholecystectomy: Their effects on our costs and ecological balance. Niger J Clin Pract. 2022 Nov;25(11):1911-1917. doi: 10.4103/njcp.njcp_387_22.
PubMed 36412300
Study at a glance
From the registry record, last updated by the sponsor on 16 Apr 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Evaluation of the Safety of Low-Flow Anesthesia Initiated Without Wash-in in Terms of Oxygenation and Depth of Anesthesia Using Arterial Blood Gas Analysis and EEG-Based PSI Monitoring
- ClinicalTrials.gov ID
- NCT07534839
- Acronym / sponsor ID
- ErzincanBinaliYildirim
- Conditions
- Low Flow Anesthesia
- Keywords
- general anesthesia, green anesthesia, low flow anesthesia
- Study type
- Interventional
- Recruitment status
- Active, not recruiting
- Enrolment
- 60 participants (estimated)
- Lead sponsor
- Erzincan Binali Yildirim UniversitesiUniversity, hospital or other
- Study start
- 1 Mar 2026 (actual)
- Primary completion
- 1 Jul 2026 (estimated)
- Study completion
- 1 Aug 2026 (estimated)
- First posted
- 16 Apr 2026 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
This study aims to evaluate whether adjusting the fresh gas flow rate to low-flow immediately after intubation, without performing a wash-in, is a reliable approach with respect to depth of anesthesia and oxygenation.
Detailed description
Low-flow anesthesia is defined as the delivery of fresh gas flow at a rate of 0.5-1 L/min on the anesthesia machine . Due to its advantages such as reducing costs, decreasing environmental pollution related to anesthetic gases, preserving mucociliary activity, softening secretions, and reducing heat loss, it has attracted considerable attention from anesthesiologists in recent years. However, the main concerns involve maintaining adequate ventilation, ensuring sufficient tissue oxygen delivery, and achieving adequate depth of anesthesia. Therefore, additional monitoring is required for the safe application of low-flow techniques. Exhaled gas volume, airway pressure, fraction of inspired oxygen (FiO₂), volatile anesthetic agent concentration, carbon dioxide concentration, and peripheral oxygen saturation (SpO₂) should be closely monitored. Arterial blood gas sampling is the gold standard for monitoring oxygenation. The Patient State Index (PSI) is a processed EEG index derived from frontal EEG signals that numerically expresses the level of anesthesia/sedation on a scale from 0 to 100. PSI is generated based on spectral and coherence analyses of data obtained from four-channel EEG monitors such as Masimo SedLine®, using advanced artifact filtering, and was developed for objective monitoring of the level of consciousness during general anesthesia. PSI values between 25 and 50 generally indicate an adequate depth of anesthesia, whereas higher values suggest a reduction in anesthetic depth.
In low-flow anesthesia, after induction the patient is connected to mechanical ventilation, and the volatile agent is adjusted to 1 MAC with 50% O₂. Subsequently, wash-in is achieved by administering fresh gas flow at 4-6 L/min for approximately 10 minutes, after which the flow is reduced. However, some studies have reported that initiating anesthesia maintenance directly with low fresh gas flow, without performing wash-in, may also be a feasible approach.
To date, no study has evaluated the reliability of initiating low fresh gas flow during mechanical ventilation without performing wash-in, using arterial blood gas analysis and PSI monitoring. This study aimed to compare the reliability of techniques involving reduction of fresh gas flow using the traditional wash-in method versus without wash-in, in terms of hypoxia and depth of anesthesia, using serial arterial blood gas measurements and PSI monitoring.
Study design
- Primary purpose
- Other
- Allocation
- Randomised
- Intervention model
- Crossover
- Masking
- None (open label)
- Number of arms
- 2
| Arm | Type | Receives |
|---|---|---|
| Group WI | No intervention | –In this group, after intubation, patients were ventilated for 10 minutes with 4 L/min fresh gas flow consisting of 2% sevoflurane and 60% O₂, after which the fresh gas flow rate was reduced to 0.75 L/min |
| Group WO | Active comparator | Device: Initiation of low-flow anesthesia without wash-in following intubationIn this group, after intubation, the fresh gas flow rate was set to 0.75 L/min with 60% O₂. The sevoflurane vaporizer was initially set to 8%, and the sevoflurane concentration was subsequently reduced according to the MAC value |
Who may qualify
- Ages
- 18 to 65 years
- Sex
- All
- Healthy volunteers
- Accepted
- Age groups
- Adult, Older adult
Key inclusion criteria (3 listed)
- ASA physical status I-II
- Cases lasting longer than 30 minutes
- Non-laparoscopic surgical procedures
Key exclusion criteria (4 listed)
- Patients with life-threatening renal, cardiac, or hepatic disease
- Patients with chronic pulmonary diseases such as asthma or COPD
- Patients with intraoperative hemodynamic instability
- Patients with a body mass index (BMI) lower than 20 or higher than 30
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| Initiation of low-flow anesthesia without wash-in following intubationAfter endotracheal intubation, fresh gas flow is set to 0.75 L/min with 60% O₂. The sevoflurane vaporizer is initially set to 8%, and the sevoflurane concentration is subsequently titrated according to the target MAC value. Anesthesia depth and oxygenation are monitored using PSI monitoring and serial arterial blood gas measurements. | Device | Group WO |
Primary outcome
Comparison of arterial oxygen partial pressure (PaO₂) values between groups
Time frame: Measured at 10, 20, 30, and 45 minutes after induction of anesthesia and before the end of surgery.
Comparison of arterial oxygen partial pressure (PaO₂) and Patient State Index (PSI) values between groups.
Comparison of Patient State Index (PSI) values between groups.
Time frame: Continuously monitored intraoperatively and recorded at 10, 20, 30, and 45 minutes after induction of anesthesia.
PSI is an EEG-based index ranging from 0 to 100. Lower values indicate deeper anesthesia; the target range is 25-50 during general anesthesia.
3 secondary outcomes
Mean alveolar concentration (MAC) values
Time frame: Continuously monitored intraoperatively and recorded at 10, 20, 30, and 45 minutes after induction of anesthesia.
Total sevoflurane consumption
Time frame: From induction of anesthesia until the end of surgery (average duration approximately X minutes).
Time to reach target MAC level
Time frame: Time (minutes) from completion of endotracheal intubation to achievement of MAC 1.0, as measured on the anesthesia monitor
Results and safety
This study is still under way. Results are not available in the source record yet.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 16 Apr 2026.
- Background: PubMed 35438367Simsek T, Derman S, Kordi RGM, Saracoglu A, Saracoglu KT. The effect of different flow levels and concentrations of sevoflurane during the wash-in phase on volatile agent consumption: a randomized controlled trial. J Clin Monit Comput. 2022 Oct;36(5):1257-1262. doi: 10.1007/s10877-022-00846-w. Epub 2022 Apr 19.
- Background: PubMed 29572589Bahar S, Arslan M, Urfalioglu A, Gisi G, Oksuz G, Bilal B, Oksuz H, Doganer A. Low-flow anaesthesia with a fixed fresh gas flow rate. J Clin Monit Comput. 2019 Feb;33(1):115-121. doi: 10.1007/s10877-018-0135-2. Epub 2018 Mar 23.
- Background: PubMed 38321515Amirfarzan H, Cassidy KJ, Moaddab M, Demin M, Schumann R, Lewis B. Assessment of seizure duration and utility of using SedLine(R) EEG tracing in veterans undergoing electroconvulsive therapy: a retrospective analysis. J Anesth Analg Crit Care. 2024 Feb 6;4(1):8. doi: 10.1186/s44158-024-00143-9.
- Background: PubMed 36450405McIlroy DR, Shotwell MS, Lopez MG, Vaughn MT, Olsen JS, Hennessy C, Wanderer JP, Semler MS, Rice TW, Kheterpal S, Billings FT 4th; Multicenter Perioperative Outcomes Group. Oxygen administration during surgery and postoperative organ injury: observational cohort study. BMJ. 2022 Nov 30;379:e070941. doi: 10.1136/bmj-2022-070941.
- Background: PubMed 37926871Dastan R, Kefeli Celik H, Doganay Z. High, Low, and Minimal Flow Anaesthesia Management: Effects on Oxygen Reserve Index and Arterial Partial Oxygen Pressure. J Coll Physicians Surg Pak. 2023 Nov;33(11):1223-1228. doi: 10.29271/jcpsp.2023.11.1223.
- Background: PubMed 33857027Varughese S, Ahmed R. Environmental and Occupational Considerations of Anesthesia: A Narrative Review and Update. Anesth Analg. 2021 Oct 1;133(4):826-835. doi: 10.1213/ANE.0000000000005504.
- Background: PubMed 36412300Kutlusoy S, Koca E, Aydin A. Reliability of low-flow anesthesia procedures in patients undergoing laparoscopic cholecystectomy: Their effects on our costs and ecological balance. Niger J Clin Pract. 2022 Nov;25(11):1911-1917. doi: 10.4103/njcp.njcp_387_22.
- Individual participant dataSharing planned: Yes. PO2, PCO2, PSI, Sevoflurane consumption, Demographic data
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Anesthesia
Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part. This study is not recruiting at the moment.
The record lists no contact. Use the official record to reach the sponsor.
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A study testing Initiation of low-flow anesthesia without wash-in following intubation in people with Low Flow Anesthesia, run by Erzincan Binali Yildirim Universitesi at 1 site in Turkey (Türkiye).
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 3 inclusion and 4 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: under way, not looking for participants, as of the sponsor's last update on 16 Apr 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in Turkey (Türkiye). Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
Are results available for this study?
This study is still under way. Results are not available in the source record yet.
How can a doctor refer a patient or contact the research team?
The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Comparison of arterial oxygen partial pressure (PaO₂) values between groups (time frame: Measured at 10, 20, 30, and 45 minutes after induction of anesthesia and before the end of surgery.). The study lists 2 primary outcomes in all. It is what the study was designed to measure, not a finding.
Where can I read the original study information?
On the ClinicalTrials.gov record for NCT07534839, which also lists 7 linked publications.
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 16 Apr 2026.