Abstract
Extracorporeal membrane oxygenation (ECMO) supports patients with severe refractory cardiac or respiratory failure but managing residual circuit blood after weaning lacks consensus. After decannulation, the oxygenator and circuit retain approximately 500–700 mL of blood, depending on tubing length, cannula size, and circuit configuration. Clinicians usually choose among direct reinfusion, cell-salvage processing, or disposal. Direct reinfusion maintains circulating red cell mass and may help avert allogeneic transfusion, especially in borderline cases, but carries the risk of reintroducing free hemoglobin, inflammatory mediators, microthrombi, and air emboli. Cell salvage offers an intermediary strategy by removing harmful elements through washing and centrifugation, but introduces delays in volume return, mechanical red cell damage, loss of platelets and clotting factors, and added cost. Discarding the blood eliminates reinfusion risks but increases reliance on banked blood, which poses risks such as immunomodulation, transfusion-associated circulatory overload (TACO), transfusion-related acute lung injury (TRALI), and resource depletion. Modified CPD blood bags have shown promise for temporarily storing blood from ECMO or RRT circuits, particularly in neonatal and pediatric patients.
Additionally, residual blood salvage during ECMO circuit changes, an often-overlooked opportunity for autologous transfusion, deserves greater emphasis. In the absence of standardized guidelines, current practice remains heterogeneous. We advocate prospective, multicenter trials comparing these strategies with endpoints including transfusion requirements, hemolysis and inflammation biomarkers, fluid balance, organ dysfunction scores, cost implications, and survival. Evidence-based protocols will enhance patient safety, reduce costs, and standardize ECMO care.
To the Editor,
We would like to highlight an important yet under-discussed issue: the lack of consensus and guidelines on managing residual circuit blood during ECMO weaning. Direct reinfusion via volume displacement maintains red cell mass and enables a form of autologous transfusion that may reduce reliance on donor blood. In hemodynamically fragile patients, even moderate additional blood volume, especially the 500–700 mL residual in modern circuits can meaningfully support cardiac output and oxygen delivery. Reinfusion through large-bore (21Fr-31Fr) cannulas provides efficient, low-resistance flow, facilitating rapid return with minimal complexity. However, circuit blood may contain hemolysis byproducts, activated cytokines, and microthrombi, all of which pose potential risks when reintroduced without filtration or washing. The cannulas commonly used in ECMO, contribute significantly to blood loss at decannulation. Once removed from the vascular system, the volume within these cannulas is lost, further increasing the likelihood of transfusion. This added loss, along with the residual circuit volume, may exceed 700 Ml, an especially relevant concern in low-weight patients or those with marginal hemoglobin levels.
Cell-salvage processing offers a compromise by cleaning the blood prior to reinfusion. Although it mitigates inflammatory and hemolytic exposure, it comes at the cost of mechanical stress to red cells, loss of platelets and coagulation factors, and delays in restoring volume, which may be critical in unstable patients. Its effectiveness was highlighted by Camarda et al., who demonstrated that cell salvage during ECMO decannulation reduced allogeneic transfusion by 0.31 units and improved haemoglobin recovery. 1
Discarding the residual blood on the other hand avoids the above reinfusion risks but results in immediate loss of red cell mass, potentially prompting the use of packed red blood cells. Maldarelli et al. emphasised that donor transfusion in ECMO patients carries immune and logistical complications that warrant reduction whenever feasible. 2 This is particularly relevant in neonates, paediatric patients, or adults with low body weight, where the proportional blood loss is significant. Modified CPD (Citrate phosphate Dextrose) blood bags may offer a low-cost, practical strategy for short-term storage and delayed reinfusion, as demonstrated by Neal et al. 3
Importantly, transfusion avoidance alone should not be the sole benchmark of efficacy. Outcome metrics must also reflect inflammatory response, fluid balance, end-organ function, and survival. Avoiding allogeneic transfusions not only minimizes immunologic and volume-related complications but also provides a notable cost advantage, conserving blood bank resources and reducing hospital expenditures. 4 Cost-effectiveness and feasibility assessments can also be incorporated into future research.
We strongly encourage the ECMO community to initiate multicentre, prospective studies assessing the safety, efficacy, and cost-effectiveness of direct reinfusion, cell salvage, and discard strategies.
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These investigations may prioritize composite endpoints, thereby incorporating patient safety, inflammatory and thrombotic risks, organ dysfunction scores, transfusion requirements, and survival, to provide a comprehensive evaluation of clinical impact. Multidisciplinary collaboration among perfusionists, cardiothoracic surgeons, anaesthesiologists, haematologists, and intensivists will be essential to developing evidence-based, consensus-driven guidelines. In the interim, individual centers can contribute by auditing existing protocols, tailoring practices based on circuit duration, cannula size, and patient-specific risk factors. Salvaging residual blood during routine ECMO circuit changeouts, a frequently overlooked source of blood loss, also represents a valuable opportunity for conservation. Standardizing residual blood management practices has the potential to improve patient outcomes, optimize resource utilization, and elevate the overall quality of ECMO care. (Figure 1). The flowchart outlines decision-making based on patient clinical parameters, stability, volume status, and circuit condition. Options include direct reinfusion, cell salvage, or discard, with the goal of optimizing blood conservation while minimizing transfusion and inflammatory risks.
Footnotes
Declaration of conflicting interests
The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Funding
The Authors received no financial support for the research, authorship, and/or publication of this article.
