In Response

Abstract

We thank Drs Ariza and Raffan for their interest in our recent publication regarding the impact of older red blood cell (RBC) transfusion on the incidence of postoperative acute kidney injury (AKI) after orthotopic liver transplantation (OLT).1,2 In this study, we found that transfusion of older RBCs significantly increased the risk of postoperative AKI in liver transplant recipients. Due to the poor coagulation function of patients with end-stage liver disease, transfusion of fresh frozen plasma (FFP) is common during OLT. However, recent studies indicated that it is a risk factor for AKI after liver transplantation.3–5 Our study is a single center, retrospective, observational study. In retrospective observational studies, there are often baseline differences between patient populations. As expected, we found that there were indeed some baseline differences between the 2 groups including the amount of transfused FFP (see Table 1). In this regard, we used the inverse probability of treatment weighting technique. After this statistical adjustment, the baseline differences including the amount of transfused FFP between the 2 groups were eliminated (see Table 3); however, the differences in the incidence of AKI and severe AKI remained significant (see Table 4). In addition, we performed sensitivity analyses by excluding patients over 60 years of age, with a Model for End-Stage Liver Disease score <10, or anhepatic phase <60 minutes. The sensitivity analyses confirmed that receiving older RBCs was a significant risk factor for postoperative AKI and severe AKI (see Table 5). AKI is one of the most common postoperative complications of OLT. We agree with Drs Ariza and Raffan that many factors contribute to the development of AKI after OLT.1 However, please note that the focus of our study was to investigate the association between the age of transfused RBCs and post-OLT AKI, which has not been reported before. Other known or unknown factors related to postoperative AKI in liver transplant recipients apparently warrant further investigation. Regarding Ariza and Raffan’s comment on the preservation method of RBC units, we also think that more studies are needed to develop better methods of blood storage. Yue Wang, MDShaanxi Provincial Center for Regenerative Medicine and Surgical EngineeringXi'an, ChinaInstitute of Advanced Surgical Technology and EngineeringXi'an, ChinaDepartment of Hepatobiliary SurgeryFirst Affiliated HospitalXi'an Jiaotong UniversityXi'an, China Rongqian Wu, MD, PhDShaanxi Provincial Center for Regenerative Medicine and Surgical EngineeringXi'an, ChinaInstitute of Advanced Surgical Technology and EngineeringXi'an, China[email protected]