Study Synopsis This protocol is formatted for ClinicalTrials.gov-style registration and manuscript-facing documentation. It is based on the uploaded Turkish ethics protocol and keeps the original core design: comparison of low-flow and minimal-flow sevoflurane anesthesia in robot-assisted laparoscopic radical prostatectomy.

Background and Rationale Robot-assisted laparoscopic radical prostatectomy (RALRP) is increasingly preferred for localized prostate cancer because of lower blood loss, reduced transfusion requirements, shorter hospitalization, and lower complication rates compared with open surgery. However, RALRP requires carbon dioxide pneumoperitoneum and steep Trendelenburg positioning, both of which may adversely affect respiratory mechanics, gas exchange, and hemodynamic stability.

Low-flow and minimal-flow anesthesia may improve humidification and warming of inspired gases, reduce inhalational agent consumption, decrease environmental waste, and potentially lower overall cost. Despite these theoretical and practical advantages, evidence remains limited regarding the physiologic safety and performance of minimal-flow sevoflurane anesthesia during long robotic pelvic surgery performed under pneumoperitoneum and steep Trendelenburg positioning.

Accordingly, this randomized prospective trial will compare low-flow (1 L/min) and minimal-flow (0.5 L/min) sevoflurane anesthesia during RALRP with respect to respiratory parameters, arterial blood gas values, intraoperative oxygenation variables, anesthetic consumption, and selected postoperative biochemical markers.

Inclusion Criteria

• Male patients aged 18 years or older.
• ASA physical status I-II.
• Scheduled for elective robot-assisted laparoscopic radical prostatectomy.
• Provision of written informed consent. Exclusion Criteria
• ASA physical status III-V.
• Severe cardiac, respiratory, hepatic, or renal disease.
• Mental status disorder or significant hearing impairment that prevents consent or communication.
• Known anxiety, depression, or other psychiatric disorder judged to interfere with study participation.
• Withdrawal of consent or investigator decision for safety reasons.