This study examines the effects of blood cell salvage (BCS) during the decannulation of veno-venous extracorporeal membrane oxygenation (VV-ECMO) on reducing transfusion requirements and improving hemoglobin (Hb) levels. VV-ECMO is a critical supportive therapy for acute respiratory failure, often necessitating packed red blood cell (PRBC) transfusions. However, PRBC transfusions carry risks such as immunological complications and high resource demands. This research evaluates BCS as a strategy to mitigate these challenges.
The research used an emulated trial framework, analyzing data from 841 patients across two UK ECMO centers between 2015 and 2022. At one center, BCS was routinely performed during VV-ECMO decannulation, while the other center followed a non-blood cell salvage (n-BCS) protocol, discarding residual blood in the ECMO circuit. This natural divergence in practice allowed a comparison of outcomes. The primary focus was on the number of PRBC units transfused within two days post-decannulation. Secondary outcomes included changes in hemoglobin levels and various inflammatory and coagulation markers.
The results showed that patients undergoing BCS required fewer PRBC transfusions compared to those managed with n-BCS. On average, BCS reduced PRBC transfusions from 0.51 to 0.2 units per patient within two days, a 0.31-unit reduction. The likelihood of requiring any PRBC transfusion decreased by 17.1%, translating to a number needed to treat (NNT) of six. Furthermore, hemoglobin levels improved significantly in the BCS group, showing a mean increase of 1.2 g/L, compared to a 3.8 g/L decrease in the n-BCS group. These findings demonstrate that BCS not only conserves blood resources but also reduces the physiological burden on patients by maintaining higher hemoglobin levels.
While BCS showed clear benefits in PRBC management, it had no significant impact on transfusion requirements for platelets or cryoprecipitate. Similarly, no differences were observed in inflammatory markers, such as C-reactive protein (CRP) and bilirubin, or coagulation factors, including activated partial thromboplastin time (APTT) and international normalized ratio (INR). These results suggest that BCS does not adversely affect coagulation or inflammation, alleviating concerns about potential complications from autotransfusion techniques.
The study’s use of an emulated trial design is noteworthy. This method emulates the conditions of a randomized controlled trial (RCT) by using observational data while controlling for confounding variables. By comparing patient outcomes between two centers with differing practices, the researchers minimized bias and ensured reliable estimates of BCS efficacy. This approach is particularly valuable in VV-ECMO, where conducting a large-scale RCT is logistically challenging due to the relatively low patient volume.
Despite its strengths, the study has limitations. The two-day follow-up period was selected to capture immediate effects of BCS on transfusion needs but may have overlooked longer-term outcomes such as delayed bleeding or sustained hemoglobin changes. Additionally, while the centers shared standardized protocols, unmeasured differences in transfusion practices or clinical decision-making may have influenced results. Nonetheless, the study provides robust evidence supporting the use of BCS during VV-ECMO decannulation.
The findings have significant implications for clinical practice. BCS offers a practical, effective solution to reducing PRBC transfusion requirements, addressing both patient safety and resource constraints. Implementing BCS in ECMO-capable centers could enhance patient outcomes, reduce transfusion-related complications, and alleviate strain on blood supplies. Furthermore, the study highlights the broader utility of trial emulation frameworks in evaluating interventions where RCTs are infeasible.
Future research should explore the economic viability of adopting BCS protocols, including cost-benefit analyses and feasibility studies in diverse healthcare settings. Longer follow-up periods could provide a more comprehensive understanding of BCS’s impact on delayed transfusion needs and long-term hematological outcomes. Additionally, comparing BCS with alternative blood conservation strategies, such as reinfusing diluted blood from the ECMO circuit, may further refine best practices.
In conclusion, this emulated trial demonstrates that BCS significantly reduces PRBC transfusion requirements and increases hemoglobin levels during VV-ECMO decannulation, without adverse effects on inflammation or coagulation. These results support the adoption of BCS as a standard practice in ECMO procedures, contributing to improved patient care and resource sustainability in critical care medicine.
