1. Title: Effects of Sodium Bicarbonate Ringer's Injection and Sodium Lactated Ringer's Injection on postoperative acute kidney injury in patients undergoing major abdominal surgery: a randomized, controlled, open-label clinical study
2. Objective: To evaluate the effect of BRS and LRS infusion on acute renal injury in patients undergoing major abdominal surgery
3. Primary outcome: Incidence of AKI at 28 days postoperative (defined as acute kidney injury, according to Kidgo 2012 definition and classification).
4. Study Design: Randomized, controlled, open-label clinical study.

1. Subjects: patients who planned to undergo elective major abdominal surgery.
2. Study data collection period: Subjects signed the consent form until 28 days after discharge or died in hospital or withdrew from the study.
3. Number of research centers/sample size: 3400 patients were planned to be included.
4. Study process: Among patients undergoing elective surgery, the researchers will include patients who meet the inclusion criteria for elective major abdominal surgery and agree to participate in the study. The data to be collected in this study will be recorded by the researcher in the eCRF, including:

(1) Data to be collected during the screening period and preoperatively: patients' basic characteristics and demographic data (2) Data to be recorded during and/or after surgery: primary study indicators, secondary indicators, and other indicators.

Inclusion Criteria:

1. ASA grade Ⅰ-Ⅲ.
2. patients aged between 20 and 70, signed informed consent form, and are willing to participate in the study.
3. BMI ≤ 30kg/m2.
4. elective major abdominal surgery for the first time (radical resection of ovarian cancer, radical resection of cervical cancer, radical resection of gastric cancer, radical resection of colorectal cancer, radical resection of bladder tumor and radical resection of prostate tumor).
5. NYHA cardiac function grade Ⅰ-Ⅲ.
6. the function of liver and kidney is normal before operation.
7. the blood coagulation function was normal before operation.
8. hemoglobin > 70g/L.
9. sinus rhythm was detected by electrocardiogram and there were no other malignant arrhythmias.

Exclusion Criteria:

1. Emergency surgery.
2. liver and kidney surgery.
3. complicated with chronic respiratory diseases and FEV1/FVC < 70%.
4. the operation time is less than 2 hours.
5. patients with mental illness or cognitive impairment.
6. uncontrolled hypertension with blood pressure higher than 180 × 100mmHg.
7. patients with hypothyroidism.
8. pregnant or lactating patients. -