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

NCT ID: NCT07328620

Last Updated: 2026-01-09

Basic Information

• Recruitment Status: COMPLETED
• Total Enrollment: 35 participants
• Study Classification: OBSERVATIONAL
• Study Start Date: 2025-03-01
• Study Completion Date: 2025-07-30

Brief Summary

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, plasma 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.

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 plasma NGAL and cystatin C, in addition to standard biochemistry profiles. Plasma NGAL levels will be measured using a validated ELISA method (Elabscience, USA), and plasma cystatin C levels will be analyzed using a particle-enhanced turbidimetric assay (Siemens Atellica Neph 630).

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.

Conditions

Acute Kidney Injury; Hypotension

Study Design

• Observational Model Type: COHORT
• Study Time Perspective: PROSPECTIVE

Eligibility Criteria

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)

• Minimum Eligible Age: 18 Years
• Maximum Eligible Age: 65 Years
• Eligible Sex: ALL
• Accepts Healthy Volunteers: Yes

Sponsors

Gazi University

OTHER

Sponsor Role: lead

Responsible Party

Galip Utku Kabacaoglu

M.D.

Responsibility Role: PRINCIPAL_INVESTIGATOR

Principal Investigators

Hasan K Pampal, M.D.

Role: STUDY_DIRECTOR

Gazi University Faculty of Medicine, Department of Anesthesiology and Reanimation

Locations

Gazi University Faculty of Medicine

Ankara, Yenimahalle, Turkey (Türkiye)

Countries

Turkey (Türkiye)

References

Khetpal S, Elias A, Alford J, et al. Anesthesia for rhinoplasty: a summary of clinical considerations, therapeutic modalities, outcomes, and future directions. JCA Adv. 2024;1:100040. doi:10.1016/j.jcadva.2024.100040.

Reference Type: BACKGROUND

Salmasi V, Maheshwari K, Yang D, Mascha EJ, Singh A, Sessler DI, Kurz A. Relationship between Intraoperative Hypotension, Defined by Either Reduction from Baseline or Absolute Thresholds, and Acute Kidney and Myocardial Injury after Noncardiac Surgery: A Retrospective Cohort Analysis. Anesthesiology. 2017 Jan;126(1):47-65. doi: 10.1097/ALN.0000000000001432.

Reference Type: BACKGROUND

PMID: 27792044 (View on PubMed)

Petrova I, Alexandrov A, Vladimirov G, Mateev H, Bogov I, Paskaleva I, Gotcheva N. NGAL as Biomarker of Clinical and Subclinical Damage of Kidney Function after Coronary Angiography. Diagnostics (Basel). 2023 Mar 20;13(6):1180. doi: 10.3390/diagnostics13061180.

Reference Type: BACKGROUND

PMID: 36980488 (View on PubMed)

Sessler DI, Bloomstone JA, Aronson S, Berry C, Gan TJ, Kellum JA, Plumb J, Mythen MG, Grocott MPW, Edwards MR, Miller TE; Perioperative Quality Initiative-3 workgroup; POQI chairs; Miller TE, Mythen MG, Grocott MP, Edwards MR; Physiology group; Preoperative blood pressure group; Intraoperative blood pressure group; Postoperative blood pressure group. Perioperative Quality Initiative consensus statement on intraoperative blood pressure, risk and outcomes for elective surgery. Br J Anaesth. 2019 May;122(5):563-574. doi: 10.1016/j.bja.2019.01.013. Epub 2019 Feb 27.

Reference Type: BACKGROUND

PMID: 30916004 (View on PubMed)

Ostermann M, Legrand M, Meersch M, Srisawat N, Zarbock A, Kellum JA. Biomarkers in acute kidney injury. Ann Intensive Care. 2024 Sep 15;14(1):145. doi: 10.1186/s13613-024-01360-9.

Reference Type: BACKGROUND

PMID: 39279017 (View on PubMed)

Other Identifiers

PerHypGU0820125

Identifier Type: -

Identifier Source: org_study_id