A method to protect kidneys of a patient undergoing cardiac surgery patient including: administrating a diuretic to the patient to increase urine output of the patient during cardiac surgery, wherein the diuretic is administered during the cardiac surgery； anesthetizing the patient with a general anesthetic during the cardiac surgery； infusing an intravenous liquid into the patient during the cardiac surgery； monitoring a rate or amount of urine output of the patient during the cardiac surgery, and automatically adjusting a rate or amount of the intravenous liquid infused into the patient to achieve or exceed a target urine output during the cardiac surgery.
