Low flow anesthesia in the prone position was safe in terms of systemic hemodynamics and did not reduce cerebral oxygenation compared to normal flow.

Patients were randomly allocated to either low fresh gas flow(LF, 0,5 L/min during maintenance) or normal flow (NF, 2 L/min)) general anesthesia. In both groups, participants were first administered with 100% oxygen at a 4 L/min flow rate. Propofol 2-2,5 mg/kg, rocuronium bromide 0,6 mg/kg, and fentanyl 1 mcg/kg IV were used for anesthesia induction.In the operating room, pulse rate, mean arterial pressure (MAP), peripheral hemoglobin oxygen saturation (spO2), and right and left side regional cerebral oxygen saturation (Masimo's O3 regional oximetry device) were measured before premedication and anesthesia induction, at 10 minutes after endotracheal intubation, at 10 minutes after prone positioning, at 1st, 2nd, 3rd, 4th and 5th hours of operation, before repositioning to supine, after the resumption of supine position and at 5 minutes after extubation. In conclusion, low flow anesthesia in patients undergoing surgery in the prone position did not cause a reduction in cerebral oxygenation compared to normal flow.

Inclusion Criteria:

• undergoing surgery in the prone position
• having an American Society of Anesthesiologists (ASA) physical status I to III
• willingness to participate in the study

Exclusion Criteria:

• having a Glasgow coma scale (GSC) score ≤ 12
• previous history of cranial surgery
• advanced cardiovascular and/or pulmonary disease
• mental retardation
• neurological disease

Patient's sex, ages and additional conditions