ALB and Hypertension: Finally, a total of 2611 patients were enrolled in this retrospective study for analysis because of missing values in covariates for preoperative clinical variables, including age, sex, BMI, ASA physical status, emergency surgery, hypertension, and preoperative laboratory data, including WBC count, hemoglobin, BUN, Cr, albumin, Na, and K. These were divided into 2088 patients (16,920 segments) for model development and 523 patients (4175 segments) for internal validation.