Objective:To evaluate the efficacy of Xuebijing Injection (血必净射液,XBJ) on the lung injury induced by cardiopulmonary bypass (CPB).Methods:Fifty patients undergoing CPB were randomized to either the saline group or XBJ group according to a random number table (25 cases in each group).The patients in the saline group received saline and patients in XBJ group received XBJ at 12 h prior to the operation,at the beginning of the operation,and at 12 h after the second injection.The PaO2/FiO2 at extubation 3 days post-operation,duration of ventilation in the intensive care unit (ICU),and lengths of stay in the ICU and hospital were recorded.The levels of inflammatory mediators including interleulin (IL)-1 β,IL-8,IL-10,and C-reactive protein (CRP) in bronchoalveolar lavage fluid (BALF) and plasma were measured.The neutrophil count and elastase neutrophil elastase in BALF were also measured.In addition,adverse events were monitored.Results:The PaO2/FiO2 in the XBJ group was higher than that in the saline group from 12 to 72 h post-operation (all P＜0.05).The blood levels of IL-1 β,IL-8,and CRP in the XBJ group from 12 to 72 h were all significantly lower than those in the saline group (all P＜0.05).In contrast,the level of the anti-inflammatory cytokine IL-10 was significantly higher in the XBJ group than in the saline group (P＜0.05).In addition,4 patients presented with atelectasis in the saline group and none in the XBJ group.Ten patients experienced mild acute respiratory distress syndrome (ARDS) during hospitalization,and 5 patients with mild ARDS were in the XBJ group (P＜0.05).Conclusion:XBJ shows protective potential against lung injury in patients who undergo CPB surgery,possibly through the downregulation of inflammatory mediators,reduction in neutrophil infiitration,and upregulation of IL-10 (Trial registry:ChiCTR-TRC-14004628).