Abstract
BackgroundExtracorporeal membrane oxygenation (ECMO) is a life-saving modality used to manage cardiopulmonary failure refractory to conventional medical and surgical therapies. Despite advances in ECMO equipment, bleeding and thrombosis remain significant complications. While the flow rate for ECMO support is well recognized, less is known about the minimum-rate requirements and haemostasis. We investigated the relationship between different ECMO flow rates, and their effect on haemolysis and coagulation.MethodsTen ex-vivo ECMO circuits were tested using donated, < 24-h-old human whole blood, with two flow rates: high-flow at 4 L/min (normal adult cardiac output; n = 5) and low-flow at 1.5 L/min (weaning; n = 5). Serial blood samples were taken for analysis of haemolysis, von Willebrand factor (vWF) multimers by immunoblotting, rotational thromboelastometry, platelet aggregometry, flow cytometry and routine coagulation laboratory tests.ResultsLow-flow rates increased haemolysis after 2 h (p = 0.02), 4 h (p = 0.02) and 6 h (p = 0.02) and the loss of high-molecular-weight vWF multimers (p = 0.01), while reducing ristocetin-induced platelet aggregation (p = 0.0002). Additionally, clot formation times were prolonged (p = 0.006), with a corresponding decrease in maximum clot firmness (p = 0.006).ConclusionsIn an ex-vivo model of ECMO, low-flow rate (1.5 L/min) altered haemostatic parameters compared to high-flow (4 L/min). Observed differences in haemolysis, ristocetin-induced platelet aggregation, high-molecular-weight vWF multimers and clot formation time suggest an increased risk of bleeding complications. Since patients are often on ECMO for protracted periods, extended-duration studies are required to characterise long-term ECMO-induced haemostatic changes.
Highlights
Extracorporeal membrane oxygenation (ECMO) is a life-saving modality used to manage cardiopulmonary failure refractory to conventional medical and surgical therapies
Platelet function (Multiplate®) adenosine diphosphate (ADP)- and TRAP-induced platelet aggregation were both significantly decreased over time from baseline to 6 h, with high- (p = 0.02 and p = 0.0008, respectively) and lowflow
RISTO-induced platelet aggregation was significantly decreased over time from baseline to 6 h with low-flow only (p = 0.0002, Fig. 3c)
Summary
Extracorporeal membrane oxygenation (ECMO) is a life-saving modality used to manage cardiopulmonary failure refractory to conventional medical and surgical therapies. Extracorporeal membrane oxygenation (ECMO) is a potentially life-saving modality that is used to provide temporary cardiopulmonary (venoarterial or VA) or pulmonary (venovenous or VV) support for critically ill patients Despite this modality’s benefits, haemostatic alterations during ECMO are common and involve both bleeding and thrombotic events [1]. Recommended flow rates for ECMO support have been well-documented [5]; less is known about how minimum blood flow rates affect haemolysis and coagulation This is especially relevant during ECMO weaning. The strategies reported by experienced ECMO centres have included (i) maintaining blood flow rates while weaning fresh (or sweep) gas flow; (ii) reducing ECMO blood pump flows while either maintaining fresh gas flows; or (iii) a combination of the two strategies These differences result from divergent expert opinions and sparsity of evidence regarding the merits of reducing pump flows to lessen shear stress to the blood elements, versus an increased risk of thrombosis. A more complete understanding of this process will help to optimise both weaning and anti-coagulation management strategies and provide justification for reducing or aiming for low-flow extracorporeal support
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