Low-flow assessment of current ECMO/ECCO2R rotary blood pumps and the potential effect on hemocompatibility

Abstract

BackgroundExtracorporeal carbon dioxide removal (ECCO2R) uses an extracorporeal circuit to directly remove carbon dioxide from the blood either in lieu of mechanical ventilation or in combination with it. While the potential benefits of the technology are leading to increasing use, there are very real risks associated with it. Several studies demonstrated major bleeding and clotting complications, often associated with hemolysis and poorer outcomes in patients receiving ECCO2R. A better understanding of the risks originating specifically from the rotary blood pump component of the circuit is urgently needed.MethodsHigh-resolution computational fluid dynamics was used to calculate the hemodynamics and hemocompatibility of three current rotary blood pumps for various pump flow rates.ResultsThe hydraulic efficiency dramatically decreases to 5–10% if operating at blood flow rates below 1 L/min, the pump internal flow recirculation rate increases 6–12-fold in these flow ranges, and adverse effects are increased due to multiple exposures to high shear stress. The deleterious consequences include a steep increase in hemolysis and destruction of platelets.ConclusionsThe role of blood pumps in contributing to adverse effects at the lower blood flow rates used during ECCO2R is shown here to be significant. Current rotary blood pumps should be used with caution if operated at blood flow rates below 2 L/min, because of significant and high recirculation, shear stress, and hemolysis. There is a clear and urgent need to design dedicated blood pumps which are optimized for blood flow rates in the range of 0.5–1.5 L/min.

Extracorporeal life support for adults with acute respiratory distress syndrome

“…Investigation of the potential benefits of ultra-protective ventilation [ 45 ] have led to renewed interest in ECCO 2 R. The technique has markedly improved in recent years [ 11 ], using more biocompatible circuits [ 10 , 46 ], dual-lumen heparin-coated catheters with a diameter closer to dialysis catheters than to ECMO cannulas [ 47 ], and ultrasonography-guided catheter insertion.…”

“…Studies are needed to investigate the impact of strategies such as larger reductions in mechanical ventilation intensity, frequent use of prone positioning, close control of respiratory drive, and ECMO without invasive mechanical ventilation. More work is needed to decrease the burden of ECMO-induced coagulopathy and associated bleeding, which is particularly important for ECCO 2 R. This includes work on improved biocompatible materials to reduce hemorrhagic or thrombotic adverse events; on pump technology to minimize shear stress, and hemolysis especially at low flows [ 76 ]. Beyond safety, the degree of benefit of ultra-protective ventilation remains to be proven [ 77 ] and large clinical trials to investigate the impact of ECCO 2 R for ARDS on outcomes are urgently needed (Table 2 ).…”

Shear‐dependent platelet aggregation size

“…The trigger threshold of shear‐induced vWF unfolding has been reported between 5000 and 5522 s −1 (Table 1). 16,17 This is approximately two to three times greater than the reported normal physiologic intravascular shear rate (<2000 s −1 ), 18‐21 but lower than those generated by LVAD (ranging from 1429 to 171 428 s −1 ) 8,22‐27 . While recent research established the relationship between shear rate and pathologic vWF degradation, precisely why bleeding complications only occur in some aVWS patients but not all remain unknown.…”

How I manage drainage insufficiency on extracorporeal membrane oxygenation

“…3 Department of Surgery, Brooke Army Medical Center, San Antonio, TX, USA. 4 Cardio-Thoracic Surgery Department, Heart & Vascular Centre, Maastricht University Medical Centre (MUMC), Cardiovascular Research Institute Maastricht (CARIM), Maastricht, The Netherlands. 5 Columbia University College of Physicians and Surgeons/ New York-Presbyterian Hospital, New York, USA.…”

“…While extracorporeal membrane oxygenation (ECMO) case volume continues to increase [1,2], management of patients receiving ECMO remains technically challenging [2,3]. Iatrogenic injury is a potential contributor to complications and poor outcomes [4][5][6][7]. Drainage insufficiency, wherein limited pump preload leads to reduced circuit blood flow, is ubiquitous, yet there is no consensus regarding treatment.…”