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According to the Extracorporeal Life Support Organization (ELSO) guidelines, pre-assembled and already primed extracorporeal membrane oxygenation (ECMO) systems can be safely stored for up to 30 days under specific conditions. This study gives a detailed overview of existing pre-assembly practices. An anonymous online survey was conducted among chief perfusionists at German ECMO centers. Forty-four of a total of 83 ECMO centers (53%) completed the survey. Thirty-three percent do not preassemble ECMO systems. Seventy-seven percent (n = 34) reported having preassembled ECMO systems readily available (30% dry preassembly/20% wet preassembly/27% wet preassembly with circulation). Half of the participating centers (50%) reported having a standard operating procedure (SOP) and the majority (57%) of chief perfusionists expressed a need for an evidence-based SOP. A maximum storage time for wet preassembled ECMO systems is established in 88% of departments. On average, wet preassembled systems are discarded after 20 days, which is below the ELSO's safe limit of 30 days. Overall, this survey reveals a heterogeneous approach regarding the practice of provisioning preassembled ECMO systems. The demand for an evidence-based SOP for the preassembly and storing of ECMO systems becomes evident, necessitating the determination of hygienic standards, regular training, and a reliable maximum storage period., Competing Interests: Disclosure: The authors have no conflicts of interest to report., (Copyright © 2024 The Author(s). Published by Wolters Kluwer Health, Inc. on behalf of the ASAIO.)

The occurrence of thrombus formation within an extracorporeal membrane oxygenator is a common complication during extracorporeal membrane oxygenation therapy and can rapidly result in a life-threatening situation due to arterial thromboembolism, causing stroke, pulmonary embolism, and limb ischemia in the patient. The standard clinical practice is to monitor the pressure at the inlet and outlet of oxygenators, indicating fulminant, obstructive clot formation indicated by an increasing pressure difference (ΔP). However, smaller blood clots at early stages are not detectable. Therefore, there is an unmet need for sensors that can detect blood clots at an early stage to minimize the associated thromboembolic risks for patients. This study aimed to evaluate if forward scattered light (FSL) measurements can be used for early blood clot detection and if it is superior to the current clinical gold standard (pressure measurements). A miniaturized in vitro test circuit, including a custom-made test chamber, was used. Heparinized human whole blood was circulated through the test circuit until clot formation occurred. Four LEDs and four photodiodes were placed along the sidewall of the test chamber in different positions for FSL measurements. The pressure monitor was connected to the inlet and the outlet to detect changes in ΔP across the test chamber. Despite several modifications in the LED positions on the test chamber, the FSL measurements could not reliably detect a blood clot within the in vitro test circuit, although the pressure measurements used as the current clinical gold standard detected fulminant clot formation in 11 independent experiments.

Clot formation inside a membrane oxygenator (MO) due to blood-to-foreign surface interaction represents a frequent complication during extracorporeal membrane oxygenation. Since current standard monitoring methods of coagulation status inside the MO fail to detect clot formation at an early stage, reliable sensors for early clot detection are in demand to reduce associated complications and adverse events. Bioimpedance analysis offers a monitoring concept by integrating sensor fibers into the MO. Herein, the feasibility of clot detection via bioimpedance analysis is evaluated. A custom-made test chamber with integrated titanium fibers acting as sensors was perfused with heparinized human whole blood in an in vitro test circuit until clot formation occurred. The clot detection capability of bioimpedance analysis was directly compared to the pressure difference across the test chamber (ΔP-TC), analogous to the measurement across MOs (ΔP-MO), the clinical gold standard for clot detection. We found that bioimpedance measurement increased significantly 8 min prior to a significant increase in ΔP-TC, indicating fulminant clot formation. Experiments without clot formation resulted in a lack of increase in bioimpedance or ΔP-TC. This study shows that clot detection via bioimpedance analysis under flow conditions in a blood-perfused test chamber is generally feasible, thus paving the way for further investigation.

Extracorporeal lung assist technology is one of the last options in critical care medicine to treat patients suffering from severe oxygenation and decarboxylation disorders. Platelet activation along with the consequent thrombus formation is a potentially life-threatening complication of this technique. To avoid platelet-dependent clot formation, this study aims at developing a microfluidic cell sorting chip that can bypass platelets prior to the membrane oxygenator of the extracorporeal lung assist device. The cell sorting chips were produced by maskless dip-in laser lithography, followed by soft lithography replication using PDMS. Citrated porcine whole blood with a clinically relevant haematocrit of 17% was used for the cell sorting experiments involving three different blood flow rates. The joint effects of flow focusing and hydrodynamic lifting forces within the cell sorting chip resulted in a reduction of up to 57% of the baseline platelet count. This cell sorting strategy is suitable for the continuous and label-free separation of red blood cells and platelets and is potentially applicable for increasing the biocompatibility and lifetime of current extracorporeal lung assist devices.

Objectives: For patients with a severe acute respiratory distress syndrome (ARDS), extracorporeal membrane oxygenation (ECMO) represents a life-saving measure. Frequently, patients with severe ARDS also show signs of severe sepsis. As blood contact with the membrane oxygenator surface leads to adverse effects due to insufficient biocompatibility partly caused by activation of platelets, coagulation factors and leucocytes, we hypothesized that these adverse effects would be amplified if septic blood in a preactivated state came into contact with the membrane oxygenator., Methods: In a previously established in vitro 12-h ECMO test system (mock loop), we used septic or healthy domestic pig blood to analyse coagulation and inflammatory parameters. Sepsis was induced by a caecal ligation and puncture model in pigs., Results: At the beginning of the mock loop experiments, the septic blood showed significantly increased thrombin-antithrombin complexes (76.9 vs 27.7 µg/l), D-dimers (1.2 vs 0.3 mg/l) and fibrinogen concentration (1.8 vs 1.5 g/l), as well as elevated extrinsic coagulation activity (shorter EXTEM-CT: 44.2 vs 57 s) and higher lactate (3.4 vs 1.5 mmol/l) and cytokine levels (interleukin-6: 827 vs 31 pg/ml) when compared with the blood from healthy animals. Despite the preactivated status of the septic blood, no further increase of coagulation activity, inflammatory response or increased oxygenator resistance was observed in comparison to the control experiments., Conclusion: Septic porcine blood was not further activated due to the contact with an oxygenator, and no increased clot formation or biocompatibility problems were observed., (© The Author 2016. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved.)

Blood clot formation inside the membrane oxygenator (MO) remains a risk in extracorporeal membrane oxygenation (ECMO). It is associated with thromboembolic complications and normally detectable only at an advanced stage. Established clinical monitoring techniques lack predictive capabilities, emphasizing the need for refinement in MO monitoring towards an early warning system. In this study, an MO was modified by integrating four sensor fibers in the middle of the hollow fiber mat bundle, allowing for bioimpedance measurement within the MO. The modified MO was perfused with human blood in an in vitro test circuit until fulminant clot formation. The optical analysis of clot residues on the extracted hollow fibers showed a clot deposition area of 51.88% ± 14.25%. This was detectable via an increased bioimpedance signal with a significant increase 5 min in advance to fulminant clot formation inside the MO, which was monitored by the clinical gold standard (pressure difference across the MO (dp-MO)). This study demonstrates the feasibility of detecting clot growth early and effectively by measuring bioimpedance within an MO using integrated sensor fibers. Thus, bioimpedance may even outperform the clinical gold standard of dp-MO as a monitoring method by providing earlier clot detection. [ABSTRACT FROM AUTHOR]

Simple Summary: Animal experiments are essential for the development and optimization of innovative biomedical soft- or hardware. These technologies, not least in the field of intensive care, contribute to an enhanced quality of care and chances of survival. One prominent example that gained public attention due to the COVID-19 pandemic is extracorporeal membrane oxygenation, in short ECMO, as it supports the heart and lungs during severe disease. Even though ECMO is already in use, the components, e.g., the oxygenator that acts as an artificial lung, need further improvement. The basic functions of new devices, e.g., the oxygenation performance, do not necessarily require living animals for the evaluation; therefore, the present study aimed to develop a post-mortem rat cadaver perfusion model exclusively using surplus animals, e.g., from in-house breeding, to reduce the number of animals used for these models, according to the animal welfare principle (the 3Rs: Replace, Reduce, Refine). It was shown that the established rat cadaver model allowed organ perfusion for up to eight hours, making it a promising model for testing new biomedical technology and, thus, a welfare-friendly alternative for existing living rat perfusion models. The development of biomedical soft- or hardware frequently includes testing in animals. However, large efforts have been made to reduce the number of animal experiments, according to the 3Rs principle. Simultaneously, a significant number of surplus animals are euthanized without scientific necessity. The primary aim of this study was to establish a post-mortem rat perfusion model using extracorporeal membrane oxygenation (ECMO) in surplus rat cadavers and generate first post vivo results concerning the oxygenation performance of a recently developed ECMO membrane oxygenator. Four rats were euthanized and connected post-mortem to a venous–arterial ECMO circulation for up to eight hours. Angiographic perfusion proofs, blood gas analyses and blood oxygenation calculations were performed. The mean preparation time for the ECMO system was 791 ± 29 s and sufficient organ perfusion could be maintained for 463 ± 26 min, proofed via angiographic imaging and a mean femoral arterial pressure of 43 ± 17 mmHg. A stable partial oxygen pressure, a 73% rise in arterial oxygen concentration and an exponentially increasing oxygen extraction ratio up to 4.75 times were shown. Considering the 3Rs, the established post-mortal ECMO perfusion rat model using surplus animals represents a promising alternative to models using live animals. Given the preserved organ perfusion, its use could be conceivable for various biomedical device testing. [ABSTRACT FROM AUTHOR]

Introduction: Due to improved technology and increased application the mortality during extracorporeal membrane oxygenation (ECMO) is constantly declining. Nevertheless, complications including haemorrhage or thrombus formation remain frequent. Local mitigation of coagulation within an ECMO system to prevent thrombus formation on ECMO components and optimizing systemic anticoagulation is an approach to reduce clotting and bleeding complications at once. Foreign surfaces of ECMO systems, activate platelets (PLTs), which besides their major role in coagulation, can trigger the formation of neutrophil extracellular traps (NETs) contributing to robust thrombus formation. The impact of a reduced PLT count on PLT activation and NET formation is of paramount importance and worth investigating. Methods: In this study platelet poor (PLT–) and native (PLT+) heparinized human blood was circulated in two identical in vitro test circuits for ECMO devices for 6 hours. PLT reduction was achieved by a centrifugation protocol prior to the experiments. To achieve native coagulation characteristics within the test circuits, the initial heparin dose was antagonized by continuous protamine administration. Results: The PLT– group showed significantly lower platelet activation, basal NET formation and limited clot stability measured via thromboelastometry. Fluorescent and scanning electron microscope imaging showed differences in clot composition. Both groups showed equal clot formation within the circuit. Conclusions: This study demonstrated that the reduction of PLTs within an ECMO system is associated with limited PLT activation and NET formation, which reduces clot stability but is not sufficient to inhibit clot formation per se. [ABSTRACT FROM AUTHOR]