Multiple logistic regression analysis identified INR [OR (95% CI) 24.46 (2.05–292.27; p = 0.012] and surgical approach [OR (95% CI) 0.48 (0.31–0.74); p < 0.001] as predictors of postoperative anemia and postoperative drop in hemoglobin (Hb). This evidence concerns the gene GSTM1 and anemia (phenotype).