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

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

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.

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