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

August 30, 2025 updated by: Elazıg Fethi Sekin Sehir Hastanesi

Comparison of Intraocular Pressure (Icare Non-contact Tonometry), Optic Nerve Sheath Diameter and Optic Perfusion Pressure of Minimal Low and High-Flow Anesthesia in Percutaneous Nephrolithotomy (Randomized, Prospective, Clinical Study)

The aim of this clinical trial is to determine the effect of minimal low-flow versus high-flow anesthesia on intraocular pressure (IOP) by non-contact tonometry, optic nerve sheath diameter (ONSD) by USG and optic perfusion pressure (OPP) in percutaneous nephrolithotomy operations. He will also learn about the effect on hemodynamic responses and arterial oxygenation. The main questions it aims to answer are:

What are the effects of low-flow anesthesia combined with prone position on intraocular pressure (IOP), optic nerve sheath diameter (ONSD) and optic perfusion pressure (OPP)? Which anesthesia flow type has optimal eye-protective results? The investigators will compare minimal low-flow and high-flow anesthesia.

Participants:

The study will include patients between the ages of 18-60 years with ASA (American Society of Anesthesiologists) risk classification I-II-III, who are scheduled for unilateral percutaneous nephrolithotomy (PCNL) operation in the Urology Clinic under elective conditions and who have given informed consent.

Study Overview

Status

Completed

Conditions

Intervention / Treatment

Detailed Description

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).

Study Type

Interventional

Enrollment (Actual)

60

Phase

  • Not Applicable

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Locations

  • Turkey (Türkiye)
    • Seçiniz
      • Elâzığ, Seçiniz, Turkey (Türkiye), 23100
        • Elazığ Fethi Sekin City Hospital

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

  • Adult

Accepts Healthy Volunteers

Yes

Description

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 .

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Screening
  • Allocation: Randomized
  • Interventional Model: Parallel Assignment
  • Masking: Double

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Other: Minimal Low-Flo Anesthesia
Group M minimal flow (n=30, fresh gas flow 0.5 L/min)
Other: minimal and high 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.
Other: High-Flow Anesthesia
Group Y high flow (n=30, fresh gas flow 4 L/min).
Other: minimal and high 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.

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Optic nerve sheath diameter (ONSD) measurements
Time Frame: Measurements will be performed serially after induction of anesthesia (T0), 1 min after intubation (T1), 30 min after supine position (T2), supine from prone position (T3) and 5 min after extubation (T4).
ONSD measurement bedside ultrasonography (POCUS) will be performed in accordance with the standardized ONSD POCUS Quality Criteria Checklist (ONSD POCUS QCC)
Measurements will be performed serially after induction of anesthesia (T0), 1 min after intubation (T1), 30 min after supine position (T2), supine from prone position (T3) and 5 min after extubation (T4).

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Intraocular pressure (IOP)
Time Frame: Measurements will be performed serially after induction of anesthesia (T0), 1 min after intubation (T1), 30 min after supine position (T2), supine from prone position (T3) and 5 min after extubation (T4).
Intraocular pressure (IOP) is calculated by spraying air into the center of the cornea with a noncontact tonometer and measuring the reflected air again by slightly flattening the cornea.
Measurements will be performed serially after induction of anesthesia (T0), 1 min after intubation (T1), 30 min after supine position (T2), supine from prone position (T3) and 5 min after extubation (T4).

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Elazıg Fethi Sekin Sehir Hastanesi

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

September 15, 2024

Primary Completion (Actual)

June 15, 2025

Study Completion (Actual)

August 20, 2025

Study Registration Dates

First Submitted

November 9, 2024

First Submitted That Met QC Criteria

November 9, 2024

First Posted (Actual)

November 12, 2024

Study Record Updates

Last Update Posted (Estimated)

September 5, 2025

Last Update Submitted That Met QC Criteria

August 30, 2025

Last Verified

July 1, 2025

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • FSCH-SB-2024/09-46

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

product manufactured in and exported from the U.S.

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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