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.
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.
Study Type
OBSERVATIONAL
Enrollment
97
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.
Baskent University Ankara Hospital
Ankara, Turkey (Türkiye)
Core body temperature (°C)
Mean intraoperative core body temperature (Degrees Celsius (°C)): Measured intraoperatively using an esophageal temperature probe.
Time frame: From induction of anesthesia until the end of surgery (approximately 1-2 hours)
Mean intraoperative heart rate (bpm)
Mean intraoperative heart rate (Beats per minute (bpm)): Measured intraoperatively via electrocardiographic monitoring.
Time frame: From induction of anesthesia until the end of surgery (approximately 1-2 hours)
Mean intraoperative mean arterial pressure (mmHg)
Mean intraoperative mean arterial pressure (Millimeters of mercury (mmHg)): Measured intraoperatively using non-invasive blood pressure monitoring.
Time frame: From induction of anesthesia until the end of surgery (approximately 1-2 hours)
Anesthetic gas consumption (mL)
Total sevoflurane consumption (Milliliters (mL)): As recorded by the anesthesia workstation.
Time frame: From induction of anesthesia until the end of surgery (approximately 1-2 hours)
Richmond Agitation-Sedation Scale (RASS) (-5 to 4)
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.
Time frame: At the end of surgery / immediate postoperative period
Anesthetic gas cost (USD or local currency)
Total intraoperative anesthetic gas cost (USD or local currency): Calculated based on total sevoflurane consumption recorded by the anesthesia workstation.
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Time frame: Intraoperative period - calculated at the end of surgery (1-2 hours).