Is Permissive Hypotension Truly Harmless? Early Biomarker Evidence of Subclinical Kidney Injury in Rhinologic Surgery

June 3, 2026 updated by: Galip Utku Kabacaoglu, Gazi University

Relationship Between Permissive Hypotension and Acute Kidney Injury in Rhinologic Surgeries: Evaluation With Serum NGAL and Cystatin C Levels

This study aims to investigate the effects of permissive hypotension, which is routinely used in rhinologic surgeries such as rhinoplasty, septoplasty, and functional endoscopic sinus surgery (FESS), on renal function. Although permissive hypotension has been widely practiced to improve surgical field visibility and reduce intraoperative blood loss, its specific definition is not standardized in the literature. In most studies, maintaining mean arterial pressure (MAP) within the range of 50-65 mmHg is considered permissive hypotension. MAP values below 60 mmHg have been associated with increased risk of cardiac and renal complications. However, in otherwise healthy patients, such episodes are frequently tolerated without clinically apparent renal dysfunction.

The kidneys have a strong compensatory reserve capacity, and early tubular injury may not be detected by conventional renal function tests such as serum creatinine. Therefore, the use of more sensitive biomarkers is necessary to detect potential subclinical injury.

In this prospective observational study, serum NGAL and cystatin C levels will be measured from routine preoperative and postoperative (12-24 hours) blood samples obtained from adult patients undergoing rhinologic procedures. A ≥25% increase in these biomarkers from baseline will be considered indicative of subclinical acute kidney injury.

Additionally, intraoperative hemodynamic data will be monitored, and the duration of MAP <60 mmHg and MAP <65 mmHg will be recorded. At the end of the procedure, surgical field conditions will be evaluated using the Boezaart Surgical Field Score. The relationship between these parameters and biomarker changes will be analyzed.

The goal of this study is to determine whether early, clinically silent renal injury may occur during permissive hypotension and to provide insight into its potential implications for future renal function. All interventions and blood samplings are part of routine care, and no additional procedures will be performed for research purposes.

Study Overview

Status

Status

Indicates the current recruitment status or the expanded access status.
Completed

Conditions

Conditions

The disease, disorder, syndrome, illness, or injury that is being studied. On ClinicalTrials.gov, conditions may also include other health-related issues, such as lifespan, quality of life, and health risks.

Detailed Description

Permissive hypotension is a commonly used anesthetic technique in rhinologic surgeries to optimize surgical conditions by reducing bleeding and improving visualization. Although widely applied, a standardized definition is lacking in the literature. Many studies define permissive hypotension as maintaining mean arterial pressure (MAP) between 50-65 mmHg. MAP values lower than 60 mmHg may compromise tissue perfusion and oxygenation, particularly in the renal medulla, possibly predisposing patients to ischemic stress. Despite this, in patients without significant comorbidities, these controlled reductions typically do not result in clinically evident kidney dysfunction, which supports the continued use of this technique in suitable cases.

However, due to the high renal reserve, subclinical kidney injury may still occur without notable changes in serum creatinine or urine output. The early detection of renal injury may be possible through biomarkers such as neutrophil gelatinase-associated lipocalin (NGAL) and cystatin C, which are more sensitive to structural renal injury. This study is designed to evaluate such potential biomarker changes during permissive hypotension applied for rhinologic surgery.

Study Design and Methods: This is a prospective observational, single-center study including 35 adult patients aged 18-65 years who are scheduled to undergo elective rhinoplasty, septoplasty, or FESS. Patients with a history of chronic kidney disease, uncontrolled hypertension or diabetes mellitus, or contraindications to hypotensive anesthesia will be excluded. Informed consent will be obtained preoperatively. All blood sampling and hemodynamic monitoring will be performed as part of routine clinical care, and no additional intervention will be introduced.

Data Collection and Measurements: Preoperative routine blood samples will be analyzed for renal biomarkers including serum NGAL and cystatin C, in addition to standard biochemistry profiles. Serum NGAL levels will be measured using a validated ELISA method (Elabscience, USA), and serum cystatin C levels will be analyzed using the Siemens Atellica Neph 630 analyzer with a nephelometric method.

Intraoperative hemodynamic variables will be recorded every 5 minutes throughout anesthesia, and total durations of MAP <60 mmHg and MAP <65 mmHg will be calculated. Postoperatively, between 12 and 24 hours, routine blood sampling will again be performed, and NGAL and cystatin C levels will be re-evaluated. At the end of surgery, surgical field visibility will be assessed by the otorhinolaryngology surgical team using the Boezaart Surgical Field Score.

Outcome Measures: The primary outcome of this study is the presence of subclinical renal injury, defined as a ≥25% increase in plasma NGAL and/or cystatin C from preoperative baseline to the postoperative 12-24-hour measurement. Secondary outcomes include the association between biomarker changes and intraoperative hypotension exposure (duration of MAP <60 mmHg and MAP <65 mmHg), as well as the relationship between hypotension and surgical field quality assessed with the Boezaart Score.

Safety and Adverse Event Monitoring: All procedures are routine clinical practices and carry no additional risk to participants. In the event of postoperative impairment of renal function, standard clinical management will be followed, including fluid optimization and nephrology consultation when appropriate.

Data Confidentiality: All collected data will be de-identified and stored securely with restricted access limited to the research team.

Study Type

Study Type

Describes the nature of a clinical study. Study types include interventional studies (also called clinical trials), observational studies (including patient registries), and expanded access.
Observational

Enrollment (Actual)

Enrollment

The number of participants in a clinical study. The "anticipated" enrollment is the target number of participants that the researchers need for the study.
35

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)
    • Yenimahalle
      • Ankara, Yenimahalle, Turkey (Türkiye), 06500
        • Gazi University Faculty of Medicine

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

Eligibility Criteria

The key requirements that people who want to participate in a clinical study must meet or the characteristics they must have. Eligibility criteria consist of both inclusion criteria (which are required for a person to participate in the study) and exclusion criteria (which prevent a person from participating). Types of eligibility criteria include whether a study accepts healthy volunteers, has age or age group requirements, or is limited by sex.

Ages Eligible for Study

  • Adult
  • Older Adult

Accepts Healthy Volunteers

Yes

Sampling Method

Non-Probability Sample

Study Population

Adult patients aged 18-65 years undergoing elective rhinologic surgery under controlled hypotension anesthesia at a single tertiary care center will be enrolled. The study population consists of otherwise healthy individuals (ASA I-II) without known kidney disease and without major comorbidities that could independently affect renal function.

Description

Inclusion Criteria:

  • Adults aged 18-65 years
  • Scheduled for elective rhinologic surgery (rhinoplasty, septoplasty, or functional endoscopic sinus surgery)
  • ASA physical status I-II
  • Able to provide written informed consent
  • Undergoing controlled hypotension anesthesia as part of routine clinical management

Exclusion Criteria:

  • Known chronic kidney disease (baseline creatinine above normal range or documented CKD)
  • Uncontrolled hypertension or uncontrolled diabetes mellitus
  • Contraindications to controlled hypotensive anesthesia
  • Pregnant or breastfeeding women
  • History of major cardiovascular disease affecting renal perfusion (e.g., severe heart failure)
  • Use of nephrotoxic medications preoperatively that may interfere with renal biomarker interpretation
  • Perioperative complications requiring deviation from routine anesthetic management (e.g., major bleeding or hemodynamic instability)

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

What is the study measuring?

Primary Outcome Measures

Primary Outcome Measures

In a clinical study's protocol, the planned outcome measure that is the most important for evaluating the effect of an intervention/treatment. Most clinical studies have one primary outcome measure, but some have more than one.
Outcome Measure
Measure Description
Time Frame
Change in serum NGAL and cystatin C concentrations indicating biomarker-defined subclinical renal stress
Time Frame: Preoperative baseline to postoperative 12-24 hours
Serum NGAL concentration (ng/mL) measured by ELISA assay and serum cystatin C concentration (mg/L) measured by automated nephelometric assay will be assessed preoperatively and at postoperative 12-24 hours. A relative increase of ≥25% from baseline will be used as an interpretive biomarker threshold, primarily for NGAL and more cautiously for cystatin C.
Preoperative baseline to postoperative 12-24 hours

Secondary Outcome Measures

Secondary Outcome Measures

In a clinical study's protocol, a planned outcome measure that is not as important as the primary outcome measure for evaluating the effect of an intervention but is still of interest. Most clinical studies have more than one secondary outcome measure.
Outcome Measure
Measure Description
Time Frame
Duration of mean arterial pressure below 60 mmHg during anesthesia
Time Frame: Intraoperative period
The total duration (minutes) of intraoperative mean arterial pressure (MAP) <60 mmHg recorded at 5-minute intervals from standard anesthesia monitoring.
Intraoperative period
Duration of mean arterial pressure below 65 mmHg during anesthesia
Time Frame: Intraoperative period
The total duration (minutes) of intraoperative mean arterial pressure (MAP) <65 mmHg recorded at 5-minute intervals from standard anesthesia monitoring.
Intraoperative period
Correlation between surgical field quality and intraoperative hypotension
Time Frame: End of surgery
Correlation between Boezaart Surgical Field Score (0-5 scale) and cumulative duration of MAP <60 mmHg and <65 mmHg (minutes).
End of surgery
Correlation between intraoperative hypotension duration and renal biomarker changes
Time Frame: Intraoperative period to postoperative 12-24 hours
Correlation between cumulative duration of MAP <60 mmHg and <65 mmHg (minutes) and percentage change in serum NGAL (ng/mL) and cystatin C (mg/L) concentrations from baseline.
Intraoperative period to postoperative 12-24 hours

Collaborators and Investigators

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

Sponsor

Sponsor

The organization or person who initiates the study and who has authority and control over the study.
Gazi University

Investigators

Investigators

A researcher involved in a clinical study. Related terms include site principal investigator, site sub-investigator, study chair, study director, and study principal investigator.
  • Study Director: Hasan K Pampal, M.D., Gazi University Faculty of Medicine, Department of Anesthesiology and Reanimation

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

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Study Major Dates

Study Start (Actual)

Study Start

The actual date on which the first participant was enrolled in a clinical study. The "anticipated" study start date is the date that the researchers think will be the study start date.
March 1, 2025

Primary Completion (Actual)

Primary Completion

The date on which the last participant in a clinical study was examined or received an intervention to collect final data for the primary outcome measure. Whether the clinical study ended according to the protocol or was terminated does not affect this date. For clinical studies with more than one primary outcome measure with different completion dates, this term refers to the date on which data collection is completed for all the primary outcome measures. The "anticipated" primary completion date is the date that the researchers think will be the primary completion date for the study.
May 30, 2025

Study Completion (Actual)

Study Completion

The date on which the last participant in a clinical study was examined or received an intervention/treatment to collect final data for the primary outcome measures, secondary outcome measures, and adverse events (that is, the last participant's last visit). The "anticipated" study completion date is the date that the researchers think will be the study completion date.
July 30, 2025

Study Registration Dates

First Submitted

First Submitted

The date on which the study sponsor or investigator first submitted a study record to ClinicalTrials.gov. There is typically a delay of a few days between the first submitted date and the record's availability on ClinicalTrials.gov (the first posted date).
December 25, 2025

First Submitted That Met QC Criteria

First Submitted That Met QC Criteria

The date on which the study sponsor or investigator first submits a study record that is consistent with National Library of Medicine (NLM) quality control (QC) review criteria. The sponsor or investigator may need to revise and submit a study record one or more times before NLM's QC review criteria are met. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
December 25, 2025

First Posted (Actual)

First Posted

The date on which the study record was first available on ClinicalTrials.gov after National Library of Medicine (NLM) quality control (QC) review has concluded. There is typically a delay of a few days between the date the study sponsor or investigator submitted the study record and the first posted date.
January 9, 2026

Study Record Updates

Last Update Posted (Actual)

Last Update Posted

The most recent date on which changes to a study record were made available on ClinicalTrials.gov. There may be a delay between when the changes were submitted to ClinicalTrials.gov by the study's sponsor or investigator (the last update submitted date) and the last update posted date.
June 4, 2026

Last Update Submitted That Met QC Criteria

Last Update Submitted That Met QC Criteria

The most recent date on which the study sponsor or investigator submitted changes to a study record that are consistent with National Library of Medicine (NLM) quality control (QC) review criteria. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
June 3, 2026

Last Verified

Last Verified

The most recent date on which the study sponsor or investigator confirmed the information about a clinical study on ClinicalTrials.gov as accurate and current. If a study with a recruitment status of recruiting; not yet recruiting; or active, not recruiting has not been confirmed within the past 2 years, the study's recruitment status is shown as unknown.
June 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

Other Study ID Numbers

Identifiers or ID numbers other than the NCT number that are assigned to a clinical study by the study's sponsor, funders, or others. These numbers may include unique identifiers from other trial registries and National Institutes of Health grant numbers.
  • PerHypGU0820125

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

IPD Plan Description

Individual participant data (IPD) will not be shared. Only de-identified, aggregated study results will be made available through scientific publications and presentations.

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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