ObjectiveTo analyze the safety and efficacy of vacuum-assisted venous drainage (VAVD) in cardiac surgery under cardiopulmonary bypass (CPB).MethodsA total of 180 patients from 3 centers between November 17, 2017 and October 1, 2018 were enrolled and randomly assigned to a VAVD group and a gravity drainage (GD) group by 1∶1 ratio. During the open-heart surgery under CPB, the VAVD group completely relied on VAVD, and the GD group used conventional GD. The primary endpoint was arterial flow before CPB, 15 min after aortic cross-clamping and rewarming to 36 °C of nasopharyngeal temperature. The secondary endpoints included hematocrit, hemoglobin concentration, blood product transfusion, etc. The safety endpoint was free hemoglobin concentration, etc.ResultsThe full analysis set contained 175 patients, 87 in the VAVD group and 88 in the GD group. Patients in the VAVD group were aged 52.8±12.0 years, and males accounted for 55.2%; patients in the GD group were aged 51.4±12.1 years, and males accounted for 59.1%. The demographic characteristics between the two groups were not statistically different. Compared to the GD group, the VAVD group could provide comparable arterial flow in CPB [average of 3 time points, 2.37±0.22 L/(min·m2) vs. 2.41±0.25 L/(min·m2), P=0.271], while not elevating free hemoglobin concentration.ConclusionVAVD can provide enough venous drainage, while not elevating free hemoglobin concentration or damaging blood.