Renal Oxygenation-Guided AKI Reduction Trial

ROGAR is an investigator-initiated, multicenter, prospective, randomized, parallel-group superiority trial enrolling approximately 1,200 adults aged 45 years or older undergoing elective open, laparoscopic, or robot-assisted hepatectomy under general anesthesia. Participants will be randomized 1:1 to renal oxygenation-guided management or usual perioperative care using a centralized allocation system stratified by study center.

All participants will undergo continuous bilateral renal regional oxygen saturation (RrSO₂) monitoring using near-infrared spectroscopy. Before randomization, kidney location and suitability for monitoring will be confirmed by ultrasound, and a baseline RrSO₂ value will be established for each side before anesthesia.

In the intervention group, RrSO₂ values will be visible to the anesthesia team. A decrease of 10% or more from the corresponding side-specific baseline will trigger confirmation of signal validity followed by a standardized stepwise management algorithm addressing clinically relevant determinants of oxygen delivery and perfusion. RrSO₂ and hemodynamic responses will be reassessed after each intervention. In the control group, RrSO₂ will be continuously recorded but concealed from the clinical team and will not guide perioperative management.

• INVOS 5100C regional oxygen saturation monitoring system (Device), also known as Near-infrared spectroscopy; bilateral renal RrSO2 monitoring: A near-infrared spectroscopy system will be used to continuously record bilateral renal regional oxygen saturation from before anesthesia induction until the end of the intraoperative monitoring period. The device is used in both study arms; display of the values differs by randomized allocation.
• RrSO2-guided perioperative management (Other): When either renal RrSO2 decreases by at least 10% from its side-specific baseline, signal artifact and sensor displacement will first be excluded. The anesthesiologist will then assess and treat reversible causes using clinically appropriate measures that may include a small isotonic crystalloid bolus based on goal-directed volume assessment, titrated norepinephrine, dobutamine, treatment of hemodynamically significant bradycardia, optimization of ventilation and oxygenation, and red blood cell transfusion when predefined criteria are met. RrSO2 and hemodynamic responses will be reassessed after each action.
• Usual perioperative management (Other): Perioperative anesthesia and hemodynamic management will follow current clinical practice and institutional standards. Renal RrSO2 values will remain hidden and will not be used for clinical decisions.

Primary outcomes

• Incidence of postoperative acute kidney injury [From the end of surgery through postoperative day 7 or hospital discharge, whichever occurs first]: Proportion of participants who develop acute kidney injury (AKI), defined by any of the following: an increase in serum creatinine of ≥0.3 mg/dL (26.5 μmol/L) within 48 hours; an increase in serum creatinine to ≥1.5 times the preoperative baseline within 7 days; or initiation of new renal replacement therapy within 7 days. Urine-output criteria will not be used for the primary outcome.

Secondary outcomes

• Severity of postoperative AKI [Through postoperative day 7 or hospital discharge, whichever occurs first]: Highest postoperative acute kidney injury (AKI) stage according to Kidney Disease: Improving Global Outcomes (KDIGO) criteria. Outcomes will include the highest KDIGO stage (no AKI, stage 1, stage 2, or stage 3) and the incidence of severe AKI, defined as KDIGO stage 2 or 3.
• Postoperative peak serum creatinine [From the end of surgery until hospital discharge, assessed up to 30 days after surgery.]: The highest serum creatinine concentration measured after surgery during the index hospitalization will be identified for each participant and reported in micromoles per liter (μmol/L).
• Persistence and recovery of AKI [From the end of surgery through postoperative day 7 or hospital discharge, whichever occurs first, assessed for up to 7 days.]: Among participants who develop AKI, the clinical course of AKI will be characterized according to prespecified definitions of transient AKI, persistent AKI, and kidney recovery.
• New Initiation of Renal Replacement Therapy Within 7 Days After Surgery [Through postoperative Day 7 or hospital discharge, whichever occurs first]: The proportion of participants who newly initiate renal replacement therapy (RRT) for acute kidney injury from the end of surgery through postoperative Day 7 or hospital discharge, whichever occurs first. Renal replacement therapy includes any form of intermittent or continuous kidney replacement therapy initiated during the assessment period.
• Renal Replacement Therapy Dependence [Through postoperative day 30]: The proportion of participants who are receiving renal replacement therapy through postoperative Day 30.
• In-hospital clinical recovery outcomes [From the end of surgery to hospital discharge,assessed up to 30 days after surgery.]: In-hospital outcomes will included ICU length of stay, postoperative hospital length of stay.
• Postoperative morbidity and complication burden [Through postoperative day 30]: Postoperative morbidity will be assessed by the Clavien-Dindo grade, and the Comprehensive Complication Index (CCI). The CCI will be calculated from all postoperative complications occurring within 30 days after surgery after assigning a Clavien-Dindo grade to each event and ranges from 0 (no complication) to 100 (death).
• Health-related quality of life [At baseline and postoperative day 30]: Health-related quality of life will be assessed using the validated Chinese version of the EuroQol 5-Dimension 5-Level (EQ-5D-5L).
• Healthcare resource use and direct medical costs [From randomization through postoperative day 30]: Total direct medical costs incurred from randomization through postoperative Day 30 will be assessed in Chinese yuan (CNY).
• All-Cause Mortality Within 30 Days After Surgery [From the end of surgery through postoperative Day 30]: The outcome will be the proportion of participants who die from any cause within 30 days after surgery. The date of death will be recorded when available.

Sex: All, ages: 45 Years to any

Inclusion Criteria:

* Age ≥45 years.
* Scheduled for elective open, laparoscopic, or robot-assisted hepatectomy.
* Planned general anesthesia with tracheal intubation and an expected surgical duration ≥2 hours.
* Stable preoperative serum creatinine available before randomization, with baseline estimated glomerular filtration rate (eGFR) ≥60 mL/min/1.73 m².
* Body mass index <30 kg/m² and bilateral renal cortex-to-skin distance ≤4 cm on ultrasound, allowing reliable bilateral renal NIRS monitoring and stable baseline RrSO₂ signals.
* American Society of Anesthesiologists physical status I-III.
* Ability to understand the study and provide written informed consent.

Exclusion Criteria:

* Pre-existing or unstable renal dysfunction, including eGFR <60 mL/min/1.73 m², AKI before randomization, unstable or progressively increasing serum creatinine, end-stage kidney disease, chronic dialysis, previous kidney transplantation, or other significant renal disease that may interfere with postoperative AKI assessment.
* Concomitant surgery expected to directly affect renal function assessment, including nephrectomy, kidney transplantation, or renal artery or vein reconstruction.
* Emergency or rescue surgery, or inability to provide valid informed consent before surgery.
* Inability to obtain reliable bilateral renal RrSO₂ monitoring because of excessive tissue depth, positioning, skin lesions, scars, infection, hematoma, severe edema, jaundice, or other technical or anatomical factors despite appropriate sensor repositioning and troubleshooting.
* Severe systemic disease or high perioperative risk, including severe cardiac or pulmonary dysfunction, recent major cardiovascular or cerebrovascular events, severe anemia, or any condition judged by the investigator to make participation unsafe.
* Participation in another interventional clinical trial that may affect perioperative management, AKI risk, or the primary outcome, or any other condition judged by the investigator to make participation unsuitable.