The Effect Of Low-Flow And Hıgh-Flow Anesthesıa On Intracranıal Pressure

April 5, 2026 updated by: Yasin Karabacak, Bursa City Hospital

Comparative Effects of High-Flow and Low-Flow Anesthesia on Optic Nerve Sheath Diameter and Cerebral Oxygenation During Laparoscopic Hysterectomy

This prospective randomized study was conducted to evaluate the effects of low-flow and high-flow anesthesia on intracranial dynamics and cerebral oxygenation in patients undergoing laparoscopic hysterectomy in the Trendelenburg position. Intracranial pressure was assessed noninvasively using optic nerve sheath diameter (ONSD), and cerebral oxygenation was monitored using near-infrared spectroscopy (NIRS). Changes in these parameters were assessed under standardized pneumoperitoneum and positioning conditions, and comparisons between anesthesia flow groups were performed according to the predefined study protocol.

Study Overview

Status

Completed

Conditions

Detailed Description

Laparoscopic surgical procedures commonly involve the establishment of pneumoperitoneum (PP) and the application of the Trendelenburg position (TP) to optimize surgical exposure. These interventions are known to increase intra-abdominal pressure and may influence venous return, intrathoracic pressure, and cerebral hemodynamics. The combined use of pneumoperitoneum and Trendelenburg positioning is considered to have the potential to increase intracranial pressure (ICP). Therefore, the intraoperative assessment of intracranial dynamics is of clinical importance.

Optic nerve sheath diameter (ONSD) measurement is a noninvasive, reproducible, and bedside-applicable method used to assess changes in intracranial pressure. ONSD is considered to correlate with ICP alterations. Cerebral oxygenation can be evaluated using near-infrared spectroscopy (NIRS), a noninvasive technique that enables continuous monitoring of cerebral tissue oxygenation.

Low-flow anesthesia is based on the reduction of fresh gas flow rates and offers several advantages, including decreased anesthetic gas consumption, preservation of heat and humidity in the respiratory tract, and reduced environmental impact. However, data regarding the effects of low-flow anesthesia on cerebral physiology and intracranial dynamics remain limited. In surgical settings where pneumoperitoneum and Trendelenburg positioning are applied, evaluating the impact of different fresh gas flow rates on intracranial pressure and cerebral oxygenation is particularly important.

This prospective, randomized study was conducted in patients scheduled for elective laparoscopic hysterectomy at Bursa City Hospital. Patients aged between 18 and 75 years with an American Society of Anesthesiologists (ASA) physical status of I-II were included. Patients meeting predefined exclusion criteria were not enrolled in the study. Written informed consent was obtained from all participants prior to inclusion.

Patients were randomized into two groups using the closed-envelope method to receive either low-flow or high-flow anesthesia. Standard monitoring, including electrocardiography, noninvasive blood pressure, peripheral oxygen saturation, and NIRS monitoring, was applied to all patients. General anesthesia induction and maintenance were performed according to standardized protocols. Mechanical ventilation was provided in volume-controlled mode, and ventilator parameters were maintained within standard ranges.

Pneumoperitoneum was established using carbon dioxide (CO₂) insufflation at a predefined pressure range and was maintained throughout the surgical procedure. Following the establishment of pneumoperitoneum, patients were placed in the Trendelenburg position at a predefined angle, which was maintained during the operation.

Optic nerve sheath diameter measurements were performed using ultrasonography with minimal pressure applied to the globe. Measurements were obtained at predefined time points. Cerebral oxygenation was continuously monitored using NIRS throughout the intraoperative period. In addition, hemodynamic and respiratory parameters, including heart rate, arterial blood pressure, end-tidal carbon dioxide (EtCO₂), and ventilatory variables, were recorded.

Within the scope of this study, the effects of low-flow and high-flow anesthesia on intracranial dynamics and cerebral oxygenation were planned to be comparatively evaluated, and the study was conducted in accordance with the predefined protocol.

Study Type

Observational

Enrollment (Actual)

64

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

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
  • Older Adult

Accepts Healthy Volunteers

No

Sampling Method

Probability Sample

Study Population

According to the study, 64 female patients aged between 18 and 75 who were to undergo laparoscopic hysterectomy were included, all of whom were classified as Class I or II according to the American Society of Anesthesiologists (ASA) physical status.

Description

Inclusion Criteria

  • Female patients aged 18-75 years
  • Scheduled for elective laparoscopic hysterectomy
  • American Society of Anesthesiologists (ASA) physical status I-II
  • Ability to provide written informed consent

Exclusion Criteria

  • Septicemia
  • Risk of malignant hyperthermia
  • Uncontrolled diabetes mellitus
  • Chronic alcohol use
  • Prolonged fasting
  • Body mass index (BMI) > 40 kg/m²
  • Intracranial space-occupying lesions (e.g., tumors, metastases, abscesses, hematomas, aneurysms)
  • History of head trauma or cerebrovascular stroke within the preceding six months
  • Known heart failure
  • Diagnosis of glaucoma
  • Prior carotid surgery or carotid artery stenosis
  • ASA physical status ≥ III
  • Requirement for massive blood transfusion
  • Conversion from volume-controlled to pressure-controlled mechanical ventilation during surgery
  • Intraoperative conversion to open surgery
  • Patient refusal to participate

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

Cohorts and Interventions

Group / Cohort
LOW-FLOW ANESTHESİA
USE OF ANESTHESIA AT A FLOW RATE OF 1 LT/MIN DURING GENERAL ANESTHESIA
HIGH-FLOW ANESTESIA
USE OF ANESTHESIA AT A FLOW RATE OF 3 L/MIN DURING GENERAL ANESTHESIA

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Optic Nerve Sheath Diameter
Time Frame: 1-4 hour
To determine the differences between the two groups of trendelenburg and pneumoperitoneum, which increase intracranial pressure.
1-4 hour

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Cerebral Oxygenation
Time Frame: 1-4 hour
To determine the effects of low-flow and high-flow anesthesia on cerebral oxygenation in conditions that increase intracranial pressure.
1-4 hour

Collaborators and Investigators

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

Sponsor

Bursa City Hospital

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)

January 1, 2024

Primary Completion (Actual)

December 1, 2024

Study Completion (Actual)

June 1, 2025

Study Registration Dates

First Submitted

March 25, 2026

First Submitted That Met QC Criteria

April 5, 2026

First Posted (Actual)

April 7, 2026

Study Record Updates

Last Update Posted (Actual)

April 7, 2026

Last Update Submitted That Met QC Criteria

April 5, 2026

Last Verified

November 1, 2023

More Information

Terms related to this study

Keywords

Other Study ID Numbers

  • 2023-17/2

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

UNDECIDED

IPD Plan Description

Protecting patient privacy and ensuring the security of patient personal information is paramount. However, in our study, some data can be shared without compromising patient safety.

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

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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