ALB and pulmonary arterial hypertension: The univariate analysis of the development group showed that the statistically significant risk factors were age, weight, RACHS-1 score, preoperative hospital stay, anaesthesia time, cardiopulmonary bypass time, aortic occlusion time and intraoperative blood transfusion (P < 0.05), whereas sex, pulmonary hypertension, preoperative total protein content and preoperative albumin were not related to pulmonary infection (Table 2).