Intraocular Pressure, Optic Nerve Sheath Diameter and Optic Perfusion Pressure of Minimal Low and High-Flow Anesthesia

Today, rapidly depleting resources and deteriorating ecosystems bring the concept of sustainability to the forefront in all areas. Anesthesia applications have also become an important evaluation subject in terms of sustainability. One of the important components of sustainable anesthesia is low-flow anesthesia. Low-flow anesthesia technique is a technique based on the re-breathing of at least half of the gas exhaled in semi-closed systems by returning at least half of the exhaled gas to the patient in the next inspiration (1). This reduces anesthetic gas consumption, reduces the carbon footprint and prevents environmental pollution. In addition, low-flow anesthesia protects mucociliary clearance mechanisms by preventing airway moisture loss and supports the physiological balance of the respiratory system (2). With the widespread use of low-flow anesthesia, research on the systemic effects of this method compared to high-flow anesthesia has also increased. Prone position may lead to undesirable effects such as increased intracranial pressure, increased intraocular pressure, increased cerebral blood flow and atelectasis. Although the effects of this position on intracranial and intraocular pressure are well known, studies on the effect of low-flow anesthesia on these parameters are limited. Therefore, how the use of low-flow anesthesia in combination with the prone position changes these effects should be evaluated in larger-scale studies (3).

Inclusion criteria

• Patients aged 18-60 years
• ASA (American Society of Anesthesiologists) risk classification I-II-III
• Unilateral percutaneous nephrolithotomy (PCNL) operation

Exclusion criteria

• Patients with drug and alcohol addiction,
• long-term smoking history (at least 1 pack/1 year),
• BMI>35,
• chronic lung disease,
• cerebrovascular disease,
• severe systemic diseases such as kidney, liver or advanced heart failure .