Evaluation of Cerebral Oxygenation During Orthopedic Surgeries Performed in the Beach Chair Position Under General Anesthesia

December 5, 2025 updated by: Nesil Coskunfirat, Akdeniz University

The goal of this observational study is to determine the correlation between cerebral oxygenation values measured by near-infrared spectroscopy (NIRS) and other routine monitoring parameters in patients placed in the semi-sitting position.

The primary questions investigated are :

Do NIRS values correlate with heart rate, invasive mean arterial pressure, and end-tidal carbon dioxide?

Do NIRS values reflect changes observed in arterial blood gas analysis?

Are cerebral perfusion-related parameters associated with patients' comorbidities such as diabetes, obesity, and hypertension?

Researchers will compare routine noninvasive monitoring (heart rate, blood pressure, peripheral oxygen saturation) with invasive arterial monitoring and NIRS to assess whether NIRS provides additional information for evaluating cerebral perfusion.

Participants will be monitored for:

Heart rate

Invasive mean arterial pressure

End-tidal carbon dioxide

Arterial blood gas changes

Cerebral oxygenation with NIRS

Patients' comorbidities (e.g., diabetes, obesity, hypertension) will also be recorded, and their association with perfusion-related parameters will be analyzed.

Study Overview

Status

Recruiting

Conditions

Intervention / Treatment

Detailed Description

Semi-sitting (beach chair) position is commonly used during orthopedic surgeries such as shoulder arthroscopy, clavicle fracture fixation, and proximal humerus operations. However, this position is associated with a risk of cerebral hypoperfusion due to gravitational redistribution of blood volume, leading to decreased mean arterial pressure at the brain level. This can result in severe complications such as visual loss, ischemic stroke, and even brain death.

Routine noninvasive monitoring methods, including heart rate, blood pressure, and peripheral oxygen saturation, are standard during anesthesia. Because of the frequent occurrence of hypotension in this position, invasive arterial pressure monitoring is recommended to detect and manage hemodynamic fluctuations more precisely. Near-infrared spectroscopy (NIRS) is a noninvasive method that allows continuous measurement of cerebral oxygenation and can identify early reductions in cerebral perfusion that may not yet be reflected in traditional monitoring parameters.

The aim of this prospective observational cohort study is to determine the correlation between cerebral oxygenation measured by NIRS and other hemodynamic parameters (heart rate, invasive mean arterial pressure, end-tidal carbon dioxide) as well as arterial blood gas analysis during orthopedic surgery performed in the semi-sitting position. Additionally, the study will evaluate the relationship between cerebral perfusion parameters and patients' comorbidities (e.g., diabetes, hypertension, obesity, and other chronic conditions) to identify potential risk factors for cerebral desaturation in this surgical position.

The study will be conducted in a single tertiary academic center. A total of 30 adult patients (ASA I-III), aged 18 years or older, scheduled for elective orthopedic surgery in the semi-sitting position will be enrolled. Standard anesthesia care will be applied to all patients, and no additional intervention will be performed beyond routine monitoring. Data collection will include continuous NIRS measurements, invasive arterial pressure, heart rate, peripheral oxygen saturation, end-tidal CO₂, and arterial blood gas results.

Statistical analysis:

Descriptive statistics will be presented as means and standard deviations for continuous variables, and frequencies for categorical variables. Normality will be assessed using the Kolmogorov-Smirnov test. Correlations between NIRS values and other parameters (mean arterial pressure, ETCO₂, heart rate, blood gas values) will be analyzed using Pearson correlation coefficients for normally distributed variables. Group comparisons will be performed using paired t-tests for parametric data and Mann-Whitney U tests for nonparametric data. Bonferroni correction will be applied where multiple comparisons are made. A p-value of <0.05 will be considered statistically significant.

Sample size was calculated using G*Power (version 3.1.9.7) with a power of 80%, alpha of 0.05, and a medium effect size (f=0.25), resulting in a minimum of 28 patients required. Data will be analyzed using SPSS version 15.0.

This study aims to contribute to identifying optimal intraoperative monitoring strategies for maintaining cerebral perfusion during orthopedic procedures performed in the semi-sitting position, particularly in patients with multiple comorbidities.

Study Type

Observational

Enrollment (Estimated)

40

Contacts and Locations

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

Study Contact

  • Name: Nesil Coşkunfırat, Prof Dr (M.D.)
  • Phone Number: +905326873426
  • Email: nesildgr@yahoo.com

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

Non-Probability Sample

Study Population

Adult patients (18 years and older, ASA I-III) undergoing orthopedic surgery in the semi-sitting position, monitored for cerebral oxygenation (NIRS), invasive arterial pressure, and routine intraoperative parameters.

Description

Inclusion Criteria:

  • Patients scheduled for orthopedic surgery in the semi-sitting position
  • ASA physical status I-III
  • Voluntary participation with informed consent

Exclusion Criteria:

  • Patients younger than 18 years
  • Patients who do not provide consent
  • History of cerebral ischemia
  • History of head trauma
  • Previous neurosurgical intervention
  • Documented carotid stenosis ≥90%
  • Previous neck surgery

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
Intervention / Treatment
Orthopedic Surgery Patients in Semi-sitting Position
ASA I-III patients undergoing orthopedic surgery in the semi-sitting position, monitored with NIRS, invasive arterial pressure, and routine parameters.
Diagnostic test: Near-Infrared Spectroscopy (NIRS) Monitoring
Cerebral oxygenation will be monitored using NIRS in addition to standard intraoperative monitoring (heart rate, invasive arterial pressure, end-tidal CO₂, and blood gas analysis).
Other Names:
  • Invasive Arterial Catheterization
  • Routine intraoperative monitoring including heart rate, non-invasive blood pressure, peripheral oxygen saturation, and end-tidal CO₂.

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Correlation Between Cerebral Oxygenation (rSO₂) Measured by NIRS and Systemic Oxygenation
Time Frame: From pre-induction baseline through post-induction and positional measurements, followed by repeated assessments every 30 minutes until the end of surgery.
The correlation between intraoperative cerebral oxygenation (regional cerebral oxygen saturation, rSO₂) (%)-measured non-invasively using near-infrared spectroscopy (NIRS) -and simultaneous systemic oxygenation assessed using arterial blood gas analysis, including: Arterial pH, PaO₂ (mmHg) and PaCO₂ (mmHg)
From pre-induction baseline through post-induction and positional measurements, followed by repeated assessments every 30 minutes until the end of surgery.
Correlation Between Cerebral Oxygenation (rSO₂) Measured by NIRS and Hemodynamic Parameters (Heart Rate and Blood Pressure)
Time Frame: From pre-induction baseline through post-induction and positional measurements, followed by repeated assessments every 30 minutes until the end of surgery.

The correlation between intraoperative cerebral oxygenation (regional cerebral oxygen saturation, rSO₂) (%)-measured non-invasively using near-infrared spectroscopy (NIRS) -and systemic hemodynamic parameters.

Systemic hemodynamic parameters will include:

  1. Heart rate (beats per minute), monitored continuously via electrocardiography (ECG)
  2. Noninvasive mean arterial pressure (mmHg), measured using an automated oscillometric device
  3. Invasive mean arterial pressure (mmHg), obtained via an arterial catheter
From pre-induction baseline through post-induction and positional measurements, followed by repeated assessments every 30 minutes until the end of surgery.

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Association of Preoperatively Documented Hypertension with Intraoperative Low Cerebral Oxygenation (rSO₂) Measured by Near-Infrared Spectroscopy
Time Frame: Preoperative period for comorbidity assessment and intraoperative period for cerebral oxygenation measurements (from pre-induction baseline to the end of surgery.
The associations between preoperatively diagnosed hypertension with the occurrence of intraoperative reductions in regional cerebral oxygen saturation (rSO₂), defined as values falling below the normal range (60-75%).
Preoperative period for comorbidity assessment and intraoperative period for cerebral oxygenation measurements (from pre-induction baseline to the end of surgery.
Association of Preoperatively Documented Diabetes Mellitus with Intraoperative Low Cerebral Oxygenation (rSO₂) Measured by Near-Infrared Spectroscopy
Time Frame: Preoperative period for comorbidity assessment and intraoperative period for cerebral oxygenation measurements (from pre-induction baseline to the end of surgery.
The associations between preoperatively diagnosed diabetes mellitus, and the occurrence of intraoperative reductions in regional cerebral oxygen saturation (rSO₂), defined as values falling below the normal range (60-75%).
Preoperative period for comorbidity assessment and intraoperative period for cerebral oxygenation measurements (from pre-induction baseline to the end of surgery.
Association of Preoperatively Documented Obesity with Intraoperative Low Cerebral Oxygenation (rSO₂) Measured by Near-Infrared Spectroscopy
Time Frame: Preoperative period for comorbidity assessment and intraoperative period for cerebral oxygenation measurements (from pre-induction baseline to the end of surgery.
The associations between preoperative obesity-defined as a body mass index (BMI) greater than 30 kg/m²-and the occurrence of intraoperative reductions in regional cerebral oxygen saturation (rSO₂), defined as values falling below the normal range (60-75%).
Preoperative period for comorbidity assessment and intraoperative period for cerebral oxygenation measurements (from pre-induction baseline to the end of surgery.

Collaborators and Investigators

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

Sponsor

Akdeniz University

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)

October 1, 2024

Primary Completion (Estimated)

May 30, 2026

Study Completion (Estimated)

May 30, 2026

Study Registration Dates

First Submitted

November 18, 2025

First Submitted That Met QC Criteria

December 5, 2025

First Posted (Actual)

December 8, 2025

Study Record Updates

Last Update Posted (Actual)

December 8, 2025

Last Update Submitted That Met QC Criteria

December 5, 2025

Last Verified

December 1, 2025

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • TBAEK-727

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

UNDECIDED

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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