Erector Spinae Oxygen Saturation and AKI After OPCAB

NCT07760129 | Not Yet Recruiting

• 1 other identifier: 4-2026-0845
• Study Type: observational
• Target: 138
• Locations: 0 countries
• Sites: N/A

Brief Summary

Acute kidney injury (AKI) is a frequent and serious complication after cardiac surgery, including off-pump coronary artery bypass (OPCAB). Because AKI is diagnosed on the basis of serum creatinine, which rises 1 to 2 days after the actual renal insult, early detection and timely intervention remain difficult. Near-infrared spectroscopy (NIRS) allows non-invasive and continuous measurement of regional tissue oxygen saturation, but the effective penetration depth of commercially available devices is only approximately 2 to 2.5 cm. In most adults the renal cortex lies deeper than this, so the signal obtained from a flank sensor may originate largely from the abdominal wall musculature rather than from renal parenchyma. This limitation may explain the inconsistent association between renal regional oxygen saturation (renal rSO2) and AKI reported so far. The erector spinae muscle at the level of the renal hilum lies within 2 cm of the skin in most patients and is supplied by the lumbar arteries and by vessels adjacent to the renal hilum. Erector spinae muscle regional oxygen saturation (ESrSO2) may therefore provide a technically more reliable NIRS signal that reflects perfusion of a vascular territory close to that of the kidney, particularly during the transient low cardiac output state induced by mechanical displacement of the heart for coronary anastomosis during OPCAB. This single-center prospective observational cohort study will enroll 138 adult patients scheduled for elective OPCAB at Severance Hospital, Yonsei University Health System, Seoul, Republic of Korea. ESrSO2 and renal rSO2 will be measured continuously with an INVOS oximeter from before anesthetic induction until the end of surgery, in addition to cerebral rSO2, which is part of standard care at the participating institution. The ESrSO2 and renal rSO2 channels will be physically masked on the monitor display during surgery, no alarms will be set for these two channels, and their values will not be used for any intraoperative clinical decision. The recorded data will be extracted after surgery using the INVOS Analytics Tool. Apart from placement of the additional NIRS sensors and a brief pre-induction ultrasound measurement of tissue depth, no study-specific procedure, laboratory test, or imaging study will be performed, and all anesthetic, surgical, and postoperative care will follow the standard institutional protocol. The primary objective is to identify which ESrSO2-derived variable best predicts postoperative AKI, defined by the Kidney Disease: Improving Global Outcomes (KDIGO) criteria within 7 days after surgery. The candidate variables are the baseline value, the intraoperative nadir, the area under the threshold (AUT), and the duration under the threshold below absolute values of 60%, 55%, and 50% and below 80% of the baseline value, calculated separately for the period before cardiac displacement and for the cardiac displacement period. Secondary objectives are to assess whether the selected ESrSO2 variable provides independent and incremental predictive information beyond a pre-specified baseline risk model, to compare the predictive performance of ESrSO2 with that of cerebral rSO2 and renal rSO2, and to evaluate the prediction of severe AKI (KDIGO stage 2 to 3) and persistent AKI (lasting 48 hours or longer). If ESrSO2 proves to be a useful early marker of AKI, it could allow real-time, non-invasive identification of patients at high risk during surgery and provide a basis for future trials of renal protective strategies.

Conditions

Acute Kidney Injury; Coronary Artery Disease; Coronary Artery Bypass, Off-Pump; Postoperative Complications; Cardiac Surgical Procedures; Spectroscopy, Near-Infrared

Keywords

rector spinae muscle regional oxygen saturation (ESrSO2); near-infrared spectroscopy (NIRS); regional oxygen saturation (rSO2; off-pump coronary artery bypass (OPCAB); acute kidney injury (AKI); KDIGO; area under the threshold (AUT); tissue oximetry

Outcome Measures

Primary Outcomes (1)

• Predictive performance (area under the receiver operating characteristic curve, AUROC) of intraoperative erector spinae muscle regional oxygen saturation (ESrSO2) variables for postoperative acute kidney injury

  Receiver operating characteristic curves are constructed for each candidate ESrSO2 variable and the AUROC values are calculated and compared in order to identify the variable with the highest predictive performance for acute kidney injury. Candidate variables are: (1) baseline ESrSO2 measured before anesthetic induction on room air; (2) intraoperative nadir ESrSO2; (3) area under the threshold (AUT), defined as the integral of the magnitude and duration of desaturation below a given threshold, for absolute values below 60%, 55%, and 50% and for values below 80% of baseline; and (4) duration under the same thresholds. AUT and duration under the threshold are calculated separately for the period before cardiac displacement and for the cardiac displacement period, which is defined as the interval from the deep pericardial stitch to heart return. All values are computed with the INVOS Analytics Tool Software. Acute kidney injury is defined according to the KDIGO criteria as an increase in

  ESrSO2 is recorded continuously from before anesthetic induction until the end of surgery (intraoperative period, up to approximately 6 hours). Acute kidney injury is assessed within 7 days after surgery.

Secondary Outcomes (5)

• Independent and incremental predictive value of the selected ESrSO2 variable for acute kidney injury after adjustment for pre-specified established risk factors

  ESrSO2 recorded intraoperatively; acute kidney injury assessed within 7 days after surgery

• Comparison of the predictive performance (AUROC) for acute kidney injury among ESrSO2, cerebral rSO2, and renal rSO2

  All regional oxygen saturation channels recorded intraoperatively; acute kidney injury assessed within 7 days after surgery

• Predictive performance of the selected ESrSO2 variable for severe acute kidney injury (KDIGO stage 2 to 3)

  Within 7 days after surgery

• Predictive performance of the selected ESrSO2 variable for persistent acute kidney injury (lasting 48 hours or longer)

  Within 7 days after surgery

• Association between the selected ESrSO2 variable and major adverse kidney events at 30 days (MAKE-30) and days alive and out of hospital at 30 days (DAOH-30)

  Within 30 days after surgery

Study Arms (1)

OPCAB cohort

Adults aged 19 years or older undergoing elective off-pump coronary artery bypass (OPCAB) surgery, in whom the skin-to-erector spinae muscle depth at the level of the left renal hilum measured by ultrasound before anesthetic induction is less than 2.0 cm. Erector spinae muscle, renal, and cerebral regional oxygen saturation are monitored continuously with near-infrared spectroscopy throughout surgery, and postoperative acute kidney injury is assessed for 7 days after surgery. A single cohort is enrolled; no comparison group is allocated, and the analysis compares participants who do and do not develop acute kidney injury within this cohort.

Device: Near-infrared spectroscopy monitoring of erector spinae muscle and renal regional oxygen saturation

Interventions

Near-infrared spectroscopy monitoring of erector spinae muscle and renal regional oxygen saturation DEVICE

Non-invasive near-infrared spectroscopy monitoring performed for research purposes only. Before anesthetic induction, ultrasonography is used to measure the depth from the skin to the erector spinae muscle and to the renal cortex at the level of the left renal hilum. In eligible participants, disposable NIRS sensors are applied over the left erector spinae muscle and over the ipsilateral renal cortex, and regional oxygen saturation is recorded continuously from before induction until the end of surgery. The erector spinae and renal channels are masked on the display and no alarms are set, so the values are not used for clinical decision-making; data are extracted after surgery with the INVOS Analytics Tool. Cerebral regional oxygen saturation is monitored as part of standard institutional care. No blood sampling, imaging, or other test is performed in addition to routine care, and no cost is charged to participants.

OPCAB cohort

Eligibility Criteria

• Age: 19 Years+
• Sex: all
• Healthy Volunteers: No
• Age Groups: Adult (18-64), Older Adult (65+)
• Sampling Method: Non-Probability Sample

Study Population

Consecutive adult patients (19 years of age or older) scheduled for elective off-pump coronary artery bypass surgery at Severance Hospital, a tertiary university hospital in Seoul, Republic of Korea, who provide written informed consent. After consent, ultrasonography performed in the operating room before anesthetic induction measures the depth from the skin to the erector spinae muscle at the level of the left renal hilum; only patients in whom this depth is less than 2.0 cm, so that a reliable near-infrared spectroscopy signal can be obtained, are finally enrolled. Patients requiring emergency or concomitant surgery, those with severe renal impairment (estimated glomerular filtration rate below 30 mL/min/1.73 m2), previous kidney transplantation, left renal disease or a solitary kidney, a body mass index above 30 kg/m2, cardiogenic shock or mechanical circulatory support, or active bleeding or infection are not eligible.

You may qualify if:

• Adults aged 19 years or older scheduled for elective off-pump coronary artery bypass (OPCAB) surgery.
• Able to receive a full explanation of the purpose and procedures of the study and to provide written informed consent voluntarily.
• Depth from the skin to the erector spinae muscle at the level of the left renal hilum, measured by ultrasonography in the operating room before anesthetic induction, of less than 2.0 cm, so that stable near-infrared spectroscopy measurement is considered feasible. Consenting patients who do not meet this criterion are not enrolled and are classified as screen failures.

You may not qualify if:

• Emergency surgery.
• Concomitant surgery performed by another department.
• Preoperative or postoperative cardiogenic shock, or need for mechanical circulatory support.
• Estimated glomerular filtration rate below 30 mL/min/1.73 m2.
• Previous kidney transplantation.
• Left renal disease or a solitary kidney.
• Body mass index above 30 kg/m2.
• Active bleeding or active infection.
• Inability to read and voluntarily consent to the informed consent document (for example, because of illiteracy, language barrier, or cognitive impairment).
• Refusal to participate in the study.

Sponsors & Collaborators

• Yonsei University: lead

MeSH Terms

Conditions

Acute Kidney Injury; Coronary Artery Disease; Postoperative Complications

Condition Hierarchy (Ancestors)

Renal Insufficiency; Kidney Diseases; Urologic Diseases; Female Urogenital Diseases; Female Urogenital Diseases and Pregnancy Complications; Urogenital Diseases; Male Urogenital Diseases; Coronary Disease; Myocardial Ischemia; Heart Diseases; Cardiovascular Diseases; Arteriosclerosis; Arterial Occlusive Diseases; Vascular Diseases; Pathologic Processes; Pathological Conditions, Signs and Symptoms

Central Study Contacts

Seo Hee Ko, Professor

CONTACT

+82-2-2095-9678; shk0207@yuhs.ac

Study Design

• Study Type: observational
• Observational Model: COHORT
• Time Perspective: PROSPECTIVE
• Sponsor Type: OTHER
• Responsible Party: SPONSOR

Study Record Dates

• First Submitted: August 6, 2026
• First Posted: August 12, 2026
• Study Start (Estimated): October 1, 2026
• Primary Completion (Estimated): October 31, 2029
• Study Completion (Estimated): December 31, 2029
• Last Updated: August 12, 2026

Record last verified: 2026-08

Data Sharing

• IPD Sharing: Will not share