Their medical records included: preoperative hypertension, diabetes mellitus (DM), coronary heart disease (CHD), chronic obstructive pulmonary disease (COPD), chronic bronchitis, rheumatoid arthritis (RA), osteoarthritis (OA), cerebral infarction, cancer, renal failure, use of corticosteroids, preoperative smoking, alcohol consumption, major surgery within 12 months; laboratory examinations and auxiliary examinations: blood type (type A, B, AB, O), routine blood test (Hb, RBC count, hematocrit), the result of preoperative low extremity vein ultrasound. This evidence concerns the gene GSTM1 and chronic obstructive pulmonary disease.