3D porous structure imaging of membranes for medical devices using scanning probe microscopy and electron microscopy: from membrane science points of view

The evolution of hemodialysis membranes (dialyzer, artificial kidney) was remarkable, since Dow Chemical began manufacturing hollow fiber hemodialyzers in 1968, especially because it involved industrial chemistry, including polymer synthesis and membrane manufacturing process. The development of hemodialysis membranes has brought about the field of medical devices as a major industry. In addition to conventional electron microscopy, scanning probe microscopy (SPM), represented by atomic force microscopy (AFM), has been used in membrane science research on porous membranes for hemodialysis, and membrane science contributes greatly to the hemodialyzer industry. Practical studies of membrane porous structure-function relationship have evolved, and methods for analyzing membrane cross-sectional morphology were developed, such as the ion milling method, which was capable of cutting membrane cross sections on the order of molecular size to obtain smooth surface structures. Recently, following the global pandemic of SARS-CoV-2 infection, many studies on new membranes for extracorporeal membrane oxygenator have been promptly reported, which also utilize membrane science researches. Membrane science is playing a prominent role in membrane-based technologies such as separation and fabrication, for hemodialysis, membrane oxygenator, lithium ion battery separators, lithium recycling, and seawater desalination. These practical studies contribute to the global medical devices industry.

Long-term ECMO, efficiency and performance of EUROSETS adult A.L.ONE ECMO oxygenator

BACKGROUND

The management of the oxygenator can be prolonged in the long-term procedures especially during extracorporeal membrane oxygenation (ECMO) for bridge to transplant or bridge to recovery. Long-term use often involves an overrun of the time of use with respect to certification of the oxygenating module of 14 days, for the maintenance of performance and efficiency of the oxygenator. The evaluation of the long-term oxygenator efficiency is complex and depends on the: patient pathology, ECMO configuration, the management of coagulation and anticoagulation, materials selection and circuit components, the structure, design and performance of the oxygenator. In this context we investgated the long-term performance of the A.L.ONE Eurosets ECMO oxygenator in relation to the parameters prodromal to replacement.

METHODS

We retrospectively collected eight years data from Anthea Hospital GVM Care & Research, Bari, Italy on the long-term use exceeding 14 days of Eurosets A.L.ONE ECMO Adult oxygenator in Polymetylpentene fiber, for ECMO procedures, including the procedures: Veno Arterial (VA) ECMO post-cardiotomy or not, veno-venous (VV) ECMO. The primary end points were the evaluation of Gas Transfer: oxygen partial pressure (PO₂) post oxygenator, Carbon dioxide partial pressure (PCO₂) post oxygenator, the oxygen transfer across the oxygenator membrane V'O₂, differential CO₂ content across oxygenator; Pressure monitoring: oxygenator pressure Drop in relation to Blood flow rate (BFR) (ΔP); Hematologic values: Hemoglobin, Fibrinogen, Platelets, aPTT, D-Dimer, LDH.

RESULTS

Nine VA ECMO patients who used the oxygenator for 18.5 days and two VV ECMO patients who used the oxygenators for 17.2 days on the seventeenth days reported average values PaO₂ (267 ± 29 mmHg); PaCO₂ (34 ± 4 mmHg) with gas blender values set to 3.8 ± 0.6 L/min of air and a FiO₂ of 78 ± 5%; the transfer across the oxygenator membrane V'O₂ was 189 ± 43 (ml/min/m²). The mean peak of partial pressure of carbon dioxide from the gas exhaust of oxygenator (P_ECO₂) was 38 ± 4 mmHg; differential CO₂ across the oxygenator "pre-oxygenator PCO₂-post-oxygenator PCO₂" (18 ± 6 mmHg); the mean blood flow rate (BFR) 4.5 ± 0.6 (L/minute); the pump revolution per minutes mean maximum rate was 4254 ± 345 (RPM); the mean pressure drop (ΔP) was 76 ± 12 mmHg; the mean peak of d-dimers (DDs) was 23.6 ± 0.8 mg / dL; the mean peak of LDH was 230 ± 55 (mg/dl); fibrinogen mean peak 223 ± 40 (mg/dl).

CONCLUSIONS

The performance of the Eurosets A.L.ONE ECMO Adult polymethylpentene fiber oxygenator in our experience has proven efficiency in terms of O₂ uptake and CO₂ removal, blood fluid dynamics, metabolic compensation and heat exchange in the long-term treatment. The device was safe without iatrogenic problems over a period of 14 days in the patients undergoing ECMO VA and in all patients undergoing VV ECMO with continuous administration of anticoagulation therapy.

Mortality rate in patients with SAR-COV-2 infection treated with extracorporeal membrane oxygenator: A systematic review and meta-analysis

BACKGROUND

Extracorporeal membrane oxygenator (ECMO) is one of the life-saving modalities for the treatment of multiple organs dysfunction, particularly the heart and the lungs.

OBJECTIVE

To evaluate the benefit of ECMO for the treatment of SAR-COV-2 infection and its outcomes, complications, and mortality rate.

METHODS

A comprehensive search for articles was performed using MEDLINE and SCOPUS from December 2019 to December 2020. Two independent reviewers selected eligible studies, extracted the data, assessed the quality of the studies, reviewed the full study protocols, and reported the findings according to the PRISMA protocol. The meta-analyses were performed using the Comprehensive Meta-Analysis software version 2.0.

RESULTS

Pooled data from 57 studies was analyzed. There were 7,035 patients with SAR-COV-2 infection with event rate of ECMO treatment was 58.10% (95%CI: 43.70-71.20). The mortality rate was 16.66% (95%CI: 11.49-23.53). The mean mortality rate of ECMO supported patients was 35.60% (95%CI: 30.60 to 41.00). Thirty-one percent (95%CI: 24.50-38.40) of the patients had venous thromboembolic events, 30.90% (95%CI: 17.90-47.80) of the patients had ECMO circuit thrombosis, and 24.50% (95%CI: 12.50-42.40) of the patients had bleeding. In the subgroup analysis, the mortality rate was higher among patients who were treated with ECMO, the pooled odds ratio was 4.47 (95%CI: 2.39-8.35, p < 0.001), and was significantly higher in Asia with an odds ratio of 7.88 (95%CI: 2.40-25.85, p = 0.001).

CONCLUSION

Mortality rate among patients who received ECMO therapy was high. A system of care, including patient selection, resource management and referral system, can impact the outcomes of ECMO therapy.

Decellularization and Recellularization Methods for Avian Lungs: An Alternative Approach for Use in Pulmonary Therapeutics

The shortage of compatible allogeneic organs and an increase in the number of patients requiring long-term lung assist devices while waiting for lung transplantation have motivated scientists to explore alternatives to bioengineer new lungs, including through decellularization and recellularization processes. A novel approach for bioengineering an extracorporeal membrane oxygenator is based on the parenchymal structure of avian lungs which utilizes a cross-current unidirectional flow of air and blood rather than bidirectional airflow, and thus eliminates dead-space ventilation. This provides more efficient gas exchange than mammalian lungs. The novel approach utilized is to decellularize avian lungs and then to recellularize with patient-derived human lung epithelial and vascular endothelial cells with the goal of creating a fully functional structure that can be used as a gas-exchange device. Here, we present avian lung decellularization and recellularization methods for chicken and emu lungs, in order to study both small- and large-scale avian lung models. For decellularization, a detergent-based protocol is utilized, and different techniques are used to validate the de- and recellularization of those lungs, including microscopy, mass spectrometry, and immunohistochemical analyses. For recellularization, techniques for seeding different human lung cell types into the decellularized scaffolds are presented.

What we learned in the past year in managing our COVID-19 patients in intensive care units?

Coronavirus disease 2019 is a pandemic, was first recognized at Wuhan province, China in December 2019. The disease spread quickly across the globe, spreading stealthily from human to human through both symptomatic and asymptomatic individuals. A multisystem disease which appears to primarily spread via bio aerosols, it has exhibited a wide clinical spectrum involving multiple organ systems with the respiratory system pathology being the prime cause of morbidity and mortality. Initially unleashing a huge destructive trail at Wuhan China, Lombardy Italy and New York City, it has now spread to all parts of the globe and has actively thrived and mutated into new forms. Health care systems and Governments responded initially with panic, with containment measures giving way to mitigation strategies. The global medical and scientific community has come together and responded to this huge challenge. Professional medical societies quickly laid out "expert" guidelines which were conservative in their approach. Many drugs were re formulated and tested quickly with the help of national and international collaborative groups, helping carve out effective treatment strategies and help build a good scientific foundation for evidence-based medicine. Out of the darkness of chaos, we now have an orderly approach to manage this disease both from a public health preventive and therapeutic standpoint. With preventive measures such as masking and social distancing to the development of highly effective and potent vaccines, the public health success of such measures has been tempered by behavioral responses and resource mobilization. From a therapy standpoint, we now have drugs that were promising but now proven ineffective, and those that are effective when given early during viral pathogenesis or later when immune dysregulation has established, and the goal is to help reign in the destructive cascade. It has been a fascinating journey for mankind and our work here recapitulates the evolution of various aspects of critical care and other inpatient practices which continue to evolve.

Enzyme mimetic microgel coating for endogenous nitric oxide mediated inhibition of platelet activation

Nitric oxide (NO) continuously generated by healthy endothelium prevents platelet activation and maintains vascular homeostasis. However, when artificial surfaces, like of extracorporeal membrane oxygenator comes in contact with blood, protein adsorption and thereby platelet activation takes place, which eventually leads to thrombus formation. To overcome this, we present an antifouling microgel coating mimicking the function of enzyme glutathione peroxidase to endogenously generate NO in the blood plasma from endogenous NO-donors and maintain a physiological NO flux. Microgels are synthesized by copolymerization of highly hydrophilic N-(2-hydroxypropyl)methacrylamide (HPMA) and glycidyl methacrylate (GMA) with diselenide crosslinks. For immobilization of the microgels on hydrophobic poly(4-methylpentene) (TPX) membranes bioengineered amphiphilic anchor peptides with free thiols are used. The anchor peptide attaches to the TPX membranes by hydrophobic interactions while the free thiols are presented for crosslinking with the microgels. The hydrophilic nature of the microgel coating prevents protein adsorption while the reversible diselenide bridges make the microgels responsive to the reducing environment and lead to the formation of reactive selenols/selenolates. The generated selenols/selenolates provide an efficient and sustained NO-release from endogenous S-nitrosothiols (RSNOs) mimicking the enzymatic function of glutathione peroxidase. On exposure to the whole blood, the microgel coating inhibited platelet activation and prolonged the blood clotting time.

Combination of polycarboxybetaine coating and factor XII inhibitor reduces clot formation while preserving normal tissue coagulation during extracorporeal life support

Blood contact with high surface area medical devices, such as dialysis and extracorporeal life support (ECLS), induces rapid surface coagulation. Systemic anticoagulation, such as heparin, is thus necessary to slow clot formation, but some patients suffer from bleeding complications. Both problems might be reduced by 1) replacing heparin anticoagulation with artificial surface inhibition of the protein adsorption that initiates coagulation and 2) selective inhibition of the intrinsic branch of the coagulation cascade. This approach was evaluated by comparing clot formation and bleeding times during short-term ECLS using zwitterionic polycarboxybetaine (PCB) surface coatings combined with either a potent, selective, bicyclic peptide inhibitor of activated Factor XII (FXII900) or standard heparin anticoagulation. Rabbits underwent venovenous ECLS with small sham oxygenators for 60 min using three means of anticoagulation (n = 4 ea): (1) PCB coating + FXII900 infusion, (2) PCB coating + heparin infusion with an activated clotting time of 220-300s, and (3) heparin infusion alone. Sham oxygenator blood clot weights in the PCB + FXII900 and PCB + heparin groups were 4% and 25% of that in the heparin group (p < 10^-6 and p < 10^-5), respectively. At the same time, the bleeding time remained normal in the PCB + FXII900 group (2.4 ± 0.2 min) but increased to 4.8 ± 0.5 and 5.1 ± 0.7 min in the PCB + heparin and heparin alone groups (p < 10^-4 and 0.01). Sham oxygenator blood flow resistance was significantly lower in the PCB + FXII900 and PCB + heparin groups than in the heparin only group (p < 10^-6 and 10^-5). These results were confirmed by gross and scanning electron microscopy (SEM) images and fibrinopeptide A (FPA) concentrations. Thus, the combined use of PCB coating and FXII900 markedly reduced sham oxygenator coagulation and tissue bleeding times versus the clinical standard of heparin anticoagulation and is a promising anticoagulation method for clinical ECLS.

An unusual case of fulminant leptospiral myocarditis: a case report

Background

Fulminant myocarditis secondary to leptospirosis is rare and associated with poor outcomes.

Case summary

We describe a 60-year-old gentleman with fulminant leptospiral myocarditis and profound cardiogenic shock requiring veno-arterial extracorporeal membrane oxygenator (VA-ECMO) support. He was given high-dose pulse steroids early on post-VA-ECMO implantation and achieved full recovery. To our knowledge, this is the first reported case of leptospiral myocarditis with multiorgan dysfunction successfully managed by VA-ECMO and high-dose pulse steroids.

Discussion

This case report highlights the potential benefits of steroids in the management of leptospiral myocarditis which requires further validation. Early aggressive supportive management with ECMO should be considered in patients with fulminant leptospiral myocarditis.

Extracorporeal membrane oxygenation in aluminum phosphide poisoning in Nepal: a case report

Background

Aluminum phosphide is a very common suicide agent in developing countries like Nepal. Due to the unavailability of a specific antidote, mortality is very high because the phosphine molecule that is formed leads to inhibition of the cytochrome oxidase enzyme system in mitochondria. Extracorporeal membrane oxygenation provides life-saving support to the cardiovascular and respiratory systems until the deadly poison is eliminated from the body.

Case presentation

We encountered one case of 67-year-old Asian woman, a known case of major depressive disorder, who presented to our center with suicidal ingestion of aluminum phosphide with cardiovascular and respiratory dysfunction. On presentation in our emergency room, she had an ejection fraction of 20% and had to be immediately intubated for respiratory failure. Based on the evidence of almost 100% mortality with aluminum phosphide poisoning, extracorporeal membrane oxygenation was initiated in our intensive care unit. Her general condition and hemodynamics gradually improved over the course of 2 days and she was weaned from extracorporeal membrane oxygenation and ventilator by post-extracorporeal membrane oxygenation days 3 and 4, respectively. After psychiatric evaluation and establishment of normal vital parameters, she was moved out of intensive care unit on post-extracorporeal membrane oxygenation day 6 and discharged to home on post-extracorporeal membrane oxygenation day 10.

Conclusions

Although this seems to be a small step in terms of global perspective, it is a giant stride for a developing country. The management of reversible but severe cardiac and respiratory failure certainly opens up newer scopes where we can ensure a quality health care service being made accessible even to the most underprivileged people.

Silicon Micropore-Based Parallel Plate Membrane Oxygenator

Extracorporeal membrane oxygenation (ECMO) is a life support system that circulates the blood through an oxygenating system to temporarily (days to months) support heart or lung function during cardiopulmonary failure until organ recovery or replacement. Currently, the need for high levels of systemic anticoagulation and the risk for bleeding are main drawbacks of ECMO that can be addressed with a redesigned ECMO system. Our lab has developed an approach using microelectromechanical systems (MEMS) fabrication techniques to create novel gas exchange membranes consisting of a rigid silicon micropore membrane (SμM) support structure bonded to a thin film of gas-permeable polydimethylsiloxane (PDMS). This study details the fabrication process to create silicon membranes with highly uniform micropores that have a high level of pattern fidelity. The oxygen transport across these membranes was tested in a simple water-based bench-top set-up as well in a porcine in vivo model. It was determined that the mass transfer coefficient for the system using SµM-PDMS membranes was 3.03 ± 0.42 mL O₂ min^-1 m^-2 cm Hg^-1 with pure water and 1.71 ± 1.03 mL O₂ min^-1 m^-2 cm Hg^-1 with blood. An analytic model to predict gas transport was developed using data from the bench-top experiments and validated with in vivo testing. This was a proof of concept study showing adequate oxygen transport across a parallel plate SµM-PDMS membrane when used as a membrane oxygenator. This work establishes the tools and the equipoise to develop future generations of silicon micropore membrane oxygenators.

Is using an open-reservoir cardiopulmonary bypass circuit after 6 days on standby safe?

OBJECTIVES

To investigate the sterility and biocompatibility of a stored open-reservoir cardiopulmonary bypass circuit maintained on standby.

METHODS

A total of four cardiopulmonary bypass circuits were assembled, primed and left to recirculate. One unit was placed in a positive-pressure operating room and the other three were placed in the intensive care unit. The primed solutions, which employed Ringer's acetate, hydroxyethylated starch and hydrate steroid, were sampled after 0, 24, 48, 72, 96, 120 and 144 h in all cardiopulmonary bypass circuits to measure the bacteria count, endotoxin count and chemical substances within the primed solution. Chemical substances were detected by assessing the following: the total organic carbon by the combustion oxidation infrared spectrometry, and molecular weight spread by gel permeation chromatography. The environments were left unattended and were uncovered during the storage period to mimic the clinical scenario.

RESULTS

There were no bacteria in any of the primed solutions, and only very minute concentrations of endotoxins were detected, both in the operating room and in the intensive care unit. The total organic carbon concentration was slightly more concentrated in the 144-h samples when compared with that in the 0-h samples. However, the molecular weight spread of the 0-h sample was identical to that in the 144-h sample.

DISCUSSION

With regard to the presence of bacteria and endotoxins, we noted that the hardshell reservoirs in the cardiopulmonary bypass circuit were effectively sealed and not invaded by bacteria. With regard to the presence of chemical substances, we noted that an increase in total organic carbon concentration was caused by bedewing, and that there was no release of chemical substances such as a polymer-coating agent, or other molecular materials in the primed solution.

CONCLUSIONS

There was no contamination or release of chemical substances in 6-day old cardiopulmonary bypass circuits maintained on standby, confirming that they are safe to use in terms of sterility and biocompatibility.

Fulminant myocarditis

Myocarditis is most often caused by a viral infection. Less common causes include other infectious agents and autoimmune diseases. Fulminant myocarditis is an unusual complication with a rapidly progressive course resulting in severe heart failure and cardiogenic shock. Fulminant myocarditis should be treated with full supportive care, using aggressive pharmacologic therapy and mechanical circulatory support, because significant improvement in left ventricular function will often occur. Cardiac transplantation is required in a small minority of patients. Cardiac magnetic resonance imaging is becoming a frequently used modality to aid in the diagnosis of myocarditis.

[Extracorporeal membrane oxygenation in primary graft dysfunction in a paediatric double lung transplant: presentation of a case]

Primary graft dysfunction is a leading cause of morbimortality in the immediate postoperative period of patients undergoing lung transplantation. Among the treatment options are: lung protective ventilatory strategies, nitric oxide, lung surfactant therapy, and supportive treatment with extracorporeal membrane oxygenation (ECMO) as a bridge to recovery of lung function or re-transplant. We report the case of a 9-year-old girl affected by cystic fibrosis who underwent double-lung transplantation complicated with a severe primary graft dysfunction in the immediate postoperative period and refractory to standard therapies. Due to development of multiple organ failure, it was decided to insert arteriovenous ECMO catheters (pulmonary artery-right atrium). The postoperative course was satisfactory, allowing withdrawal of ECMO on the 5th post-surgical day. Currently the patient survives free of rejection and with an excellent quality of life after 600 days of follow up.