Intraoperative Assessment of Renal Tissue Oxygenation Using NIRS

Intraoperative Assessment of Renal Tissue Oxygenation Using Near-Infrared Spectroscopy During Liver Transplantation and Its Relationship With Hemodynamic Parameters: A Prospective Observational Study

The kidney is one of the most vital organs in the human body. Renal perfusion is primarily supplied by the renal artery, while the removal of metabolites and venous drainage are provided by the renal vein. Although anatomical variations may exist, the renal artery typically originates from the abdominal aorta. In patients undergoing liver transplantation, renal function may be affected by multiple factors. Impairment of renal function significantly influences postoperative mortality, morbidity, graft survival, and length of hospital stay.

Intraoperative assessment of renal perfusion has traditionally relied on monitoring hourly urine output and serum renal function tests. However, these methods may be insufficient and delayed in evaluating renal function, particularly during clamping of the inferior vena cava for hepatic graft venous anastomosis. Although Doppler ultrasonography can provide information regarding blood flow, it does not offer direct insight into the adequacy of tissue perfusion.

Near-infrared spectroscopy (NIRS) is a non-invasive technique that has gained increasing attention in recent years due to its ability to accurately assess tissue oxygenation. Based on the Beer-Lambert law, NIRS enables the measurement of tissue oxygen saturation without the need for invasive procedures. The technique requires no intervention and is not associated with known complications or adverse effects.

NIRS is most commonly used in clinical practice to assess cerebral oxygenation via measurements obtained from the frontal region. The aim of the present study is to evaluate renal oxygenation using near-infrared spectroscopy and to determine whether this technique provides clinically useful information during the liver transplantation procedure.

Study Overview

• Status: Completed
• Conditions: Liver Transplant, Complications; Renal Failure Acute Chronic

Detailed Description

Near-infrared spectroscopy (NIRS) is a non-invasive and user-friendly technique that enables real-time monitoring of tissue oxygen content. It is most commonly used in clinical practice to assess cerebral tissue oxygenation, particularly in cardiac surgery, where significant hemodynamic fluctuations are frequently encountered. NIRS measures cerebral tissue oxygen saturation from the frontal region and reflects the balance between local cerebral oxygen supply and demand. Light applied to the forehead is emitted within the near-infrared spectrum and detected by sensors positioned at specific distances from the light source. Using a modified version of the Beer-Lambert law, NIRS provides a measurement of oxygenated hemoglobin concentration relative to total hemoglobin concentration. Algorithms are subsequently applied to the raw data to generate a quantitative estimate of tissue oxygen saturation.

Numerous studies have demonstrated a correlation between cerebral desaturation and postoperative neurological complications. Consequently, specific management algorithms have been developed for the use of NIRS in cardiac surgery. In the presence of cerebral desaturation, recommended interventions include correction of cannula positioning, elevation of mean arterial pressure, increasing the inspired oxygen concentration, normalization of PaCO₂ levels, correction of hemoglobin concentration, augmentation of cardiac output, and reduction of cerebral metabolic rate.

Renal oxygen supply is primarily provided via the renal artery, while venous drainage occurs through the renal veins into the inferior vena cava. Adequate renal perfusion during liver transplantation is essential to minimize postoperative renal complications. For vascular anastomosis of the liver graft, clamping of the inferior vena cava is required, a process that results in significant hemodynamic alterations and impaired renal venous drainage. These changes may substantially affect renal oxygenation and perfusion. Although renal blood flow adequacy can be indirectly assessed by monitoring urine output after reperfusion, this method does not allow for objective evaluation of renal tissue oxygenation. We hypothesize that intraoperative monitoring of renal tissue oxygenation using NIRS may provide valuable real-time information and contribute to the early identification of postoperative acute kidney injury.

• Study Type: Observational
• Enrollment (Actual): 41

Contacts and Locations

Study Locations

• Turkey (Türkiye)
  • Malatya, Turkey (Türkiye), 44280
    • Inonu University Liver Transplant Institute

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: No

• Sampling Method: Non-Probability Sample

Study Population

Patients undergoing elective liver transplantation between the ages of 18 and 65

Description

This prospective observational study was conducted at the Inönü University Liver Transplant Institute between 2022 and 2023, following approval by the Malatya Clinical Research Ethics Committee (Approval No. 2022/118).

Inclusion Criteria:

• Patients aged 18-65 scheduled for elective liver transplantation.
• American Society of Anesthesiologists (ASA) physical status III-IV were enrolled.

Exclusion Criteria:

• Patients undergoing emergency liver transplantation,
• Advanced preexisting renal dysfunction
• İndividuals with significant cardiovascular instability

Study Plan

How is the study designed?

Number of groups / cohorts

1

Cohorts and Interventions

Group / Cohort
Group1; A total of 41 adult patients (≥18 years) scheduled for elective orthotopic liver transplantation (OLT) and classified as American Society of Anesthesiologists (ASA) physical status III-IV were enrolled to study between 2024 and 2025

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Renal O3	Renal parenchymal oxygen saturation was measured using a Masimo™ NIRS probe enclosed in a sterile sheath. During surgical dissection, the probe was positioned vertically on the Gerota's fascia overlying the kidney.	Measurements were recorded at three predefined surgical phases: • T0: Pre-anhepatic phase (beginning of dissection) • T1: Anhepatic phase (after clamping of the inferior vena cava and portal vein) • T2: Neohepatic phase (after graft reperfusion and compl
Cr	Renal function was evaluated using serum creatinine levels	Renal function was evaluated using serum creatinine levels measured preoperatively, at postoperative 24 hours, and at postoperative week 1.

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
HR	Heart Rate	During surgery: • T0: Pre-anhepatic phase (beginning of dissection) • T1: Anhepatic phase (after clamping of the inferior vena cava and portal vein) • T2: Neohepatic phase (after graft reperfusion and completion of vascular anastomoses)
MAP	mean arterial pressure (mmHg) (via invasive arterial pressure monitoring from the radial artery)	During surgery: • T0: Pre-anhepatic phase (beginning of dissection) • T1: Anhepatic phase (after clamping of the inferior vena cava and portal vein) • T2: Neohepatic phase (after graft reperfusion and completion of vascular anastomoses)
CI	Cardiac Index (L/min/m²) (via PICCO flotrac monitoring platform)	During surgery: • T0: Pre-anhepatic phase (beginning of dissection) • T1: Anhepatic phase (after clamping of the inferior vena cava and portal vein) • T2: Neohepatic phase (after graft reperfusion and completion of vascular anastomoses)
SVV	Stroke volume variation (%) (via PICCO flotrac monitoring platform)	During surgery: • T0: Pre-anhepatic phase (beginning of dissection) • T1: Anhepatic phase (after clamping of the inferior vena cava and portal vein) • T2: Neohepatic phase (after graft reperfusion and completion of vascular anastomoses)

Collaborators and Investigators

• Sponsor: Inonu University

Publications and helpful links

General Publications

• Bevan PJ. Should Cerebral Near-infrared Spectroscopy be Standard of Care in Adult Cardiac Surgery? Heart Lung Circ. 2015 Jun;24(6):544-50. doi: 10.1016/j.hlc.2015.01.011. Epub 2015 Feb 7.
• Fischer GW, Silvay G. Cerebral oximetry in cardiac and major vascular surgery. HSR Proc Intensive Care Cardiovasc Anesth. 2010;2(4):249-56.
• Edmonds HL Jr. Pro: all cardiac surgical patients should have intraoperative cerebral oxygenation monitoring. J Cardiothorac Vasc Anesth. 2006 Jun;20(3):445-9. doi: 10.1053/j.jvca.2006.03.003. No abstract available.

Study record dates

Study Major Dates

• Study Start (Actual): December 1, 2022
• Primary Completion (Actual): July 15, 2024
• Study Completion (Actual): August 7, 2025

Study Registration Dates

• First Submitted: February 2, 2026
• First Submitted That Met QC Criteria: February 12, 2026
• First Posted (Actual): February 13, 2026

Study Record Updates

• Last Update Posted (Actual): February 13, 2026
• Last Update Submitted That Met QC Criteria: February 12, 2026
• Last Verified: July 1, 2024

More Information

Terms related to this study

• Keywords: NIRS; Liver Transplantation; Renal Function
• Other Study ID Numbers: Inonu Kidney03

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: YES
• IPD Plan Description: Demographic data including age, sex, and body mass index (BMI), as well as comorbidities, duration of surgery, and length of intensive care unit (ICU) stay, HR, MAP, Renal O3, creatin values

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No