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NCT Number: NCT07465146

Effects of Minimal and Metabolic Flow Sevoflurane Anesthesia in Gynecological Surgery Patients

The aim of this study is to observe the effects of minimal and metabolically required basal anesthetic gas flow rates delivered by the anesthesia workstation under general anesthesia on body temperature, blood pressure, and heart rate during surgery.

It also aims to evaluate the impact of reducing excessive delivery of anesthetic gases, air, and oxygen beyond the patient's physiological needs during general anesthesia on minimizing the harmful effects of anesthetic gases on the environment, climate, and global warming, as well as on contributing positively to hospital costs.

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Key information

Conditions

Low-flow Anesthesia

Age range

18 year–65 year

Sex eligibility

Female

Study type

Observational

Primary location

Baskent University Ankara Hospital

Ankara, 06490, Turkey (Türkiye)

About this study

This prospective randomized study will be conducted in adult female patients undergoing elective gynecological surgery under general anesthesia. Following standard intravenous induction and endotracheal intubation, anesthesia will be maintained with sevoflurane using an advanced anesthesia workstation capable of delivering minimal and metabolic fresh gas flow rates.

After achieving the target anesthetic depth guided by minimum alveolar concentration (MAC) and MAC Brain monitoring, patients will be randomized to receive either minimal-flow (0.5 L/min) or metabolic-flow (0.3 L/min) fresh gas anesthesia. Randomization will be performed using an internet-based randomization tool.

Standard intraoperative monitoring will be applied in all patients, including electrocardiography, non-invasive blood pressure monitoring, pulse oximetry, capnography, anesthetic gas analysis, and esophageal temperature monitoring. Hemodynamic and respiratory parameters will be recorded at predefined time intervals throughout surgery. Sevoflurane consumption will be automatically calculated by the anesthesia workstation.

At the end of surgery, fresh gas flow will be increased to eliminate residual anesthetic gases, and patients will be extubated according to standard clinical criteria. Postoperative monitoring will continue in the post-anesthesia care unit.

The total study duration for each participant includes the intraoperative period and approximately 30 minutes of postoperative monitoring.

Who can participate

Healthy volunteers accepted: No

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

  • Female patients aged 18-65 years
  • Undergoing elective gynecologic surgery under general anesthesia (including hysterectomy and/or oophorectomy)

Exclusion criteria

  • Pregnant patients
  • Patients with advanced cardiac disease
  • Patients with advanced renal disease
  • Patients with advanced hepatic disease
  • Patients with advanced respiratory disease
  • Severe obesity
  • Heavy smokers
  • Excessive alcohol consumption
  • Known allergic sensitivity to halogenated anesthetic gases
  • Use of medications that may interact with volatile anesthetics
  • History of or susceptibility to malignant hyperthermia or neuromuscular disorders

Treatment and study plan

low flow anesthesia

Procedure

Adjustment of fresh gas flow rates during general anesthesia using a modern anesthesia workstation (Getinge Flow-C). Patients will be randomized to receive anesthesia with either minimal flow (0.5 L/min) or metabolic flow (0.3 L/min). All other anesthetic agents and monitoring parameters will remain standardized according to institutional protocols.

Other names: Metabolic Flow (0.3 L/min), Minimal Flow (0.5 L/min)

Primary outcomes

  1. Core body temperature (°C)

    Time frame: From induction of anesthesia until the end of surgery (approximately 1-2 hours)

    Mean intraoperative core body temperature (Degrees Celsius (°C)):

    Measured intraoperatively using an esophageal temperature probe.

  2. Mean intraoperative heart rate (bpm)

    Time frame: From induction of anesthesia until the end of surgery (approximately 1-2 hours)

    Mean intraoperative heart rate (Beats per minute (bpm)): Measured intraoperatively via electrocardiographic monitoring.

  3. Mean intraoperative mean arterial pressure (mmHg)

    Time frame: From induction of anesthesia until the end of surgery (approximately 1-2 hours)

    Mean intraoperative mean arterial pressure (Millimeters of mercury (mmHg)): Measured intraoperatively using non-invasive blood pressure monitoring.

  4. Anesthetic gas consumption (mL)

    Time frame: From induction of anesthesia until the end of surgery (approximately 1-2 hours)

    Total sevoflurane consumption (Milliliters (mL)): As recorded by the anesthesia workstation.

  5. Richmond Agitation-Sedation Scale (RASS) (-5 to 4)

    Time frame: At the end of surgery / immediate postoperative period

    Richmond Agitation-Sedation Scale (RASS) (-5 to 4): The RASS is a 10-point scale ranging from -5 to +4. Negative scores (-1 to -5) indicate increasing levels of sedation, with -5 indicating an unarousable patient. Positive scores (+1 to +4) indicate increasing levels of agitation, with +4 indicating combative behavior. Scores closer to 0 reflect better recovery quality.

Secondary outcomes

  1. Anesthetic gas cost (USD or local currency)

    Time frame: Intraoperative period - calculated at the end of surgery (1-2 hours).

    Total intraoperative anesthetic gas cost (USD or local currency):

    Calculated based on total sevoflurane consumption recorded by the anesthesia workstation.

Sponsors and collaborators

Lead sponsor

Baskent University

Other

Registry information

Official study title

Comparative Analysis of Sevoflurane-Based Minimal and Metabolic Flow Anaesthesia: A Prospective Randomized Study in a Gynecological Surgery Patient Cohort

Important dates

Study start
2024
Primary completion
2025
Study completion
2025
First posted
Mar 11, 2026
Registry last updated
Mar 11, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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