REN and Hyponatremia: Adding 11 key clinical variables (e.g., age, sex, estimated glomerular filtration rate (eGFR), albuminuria, hyponatremia, hypoalbuminemia, anemia, diabetes, renin-angiotensin-aldosterone inhibitors, emergency surgery, and the estimated surgery time) improved the model’s performance (AUROC: discovery cohort 0.765, validation cohort 0.716 and 0.761).