Listen to this informative and stimulating webinar to receive continuing education credits from your respective European and American associations (see final paragraph). 

In a Transonic-hosted webinar “ECMO Management of Oxygenator Clotting”  held recently, three ECMO therapy experts discussed management of COVID-19 patients at their respective institutions. Dr. Professor Philipp M. Lepper discussed treatment of COVID-19 patients in the ICU and ECMO units at his Saarland University Hospital in Homburg, Germany. Two perfusionists Rik Hendrix, MSc, from Maastricht University Medical Center, Maastricht in the Netherlands, and Kenny van Zwam, European certified clinical perfusionist from UZ Leuven, Belgium also discussed their experiences with COVID-19 patients on ECMO. 

The webinar was moderated by the Clinical Specialist for Transonic cardiopulmonary and ECMO products Sierra Coyle, MS, RRT-NPS, who led off the discussion with a brief introduction of Transonic’s history, the evolution of its biomedical products to improve the lives of patients worldwide, and the company’s long-standing focus on education stemming from its roots at Cornell University. Sierra noted that Transonic’s latest product, the ELSA Monitor, provides measurements of recirculation and true delivered flow during VV ECMO, and also measures oxygenator clot volume in all ECMO circuits. 

Saarland University Hospital Experience

Then Professor Dr. Lepper, senior physician, pulmonologist and intensivist at Saarland University Hospital presented his topic, “The Management of Ventilation and Hemodynamic Monitoring of COVID-19 Patients” in his hospital’s 16-bed ECMO unit. To date, their ICU unit has treated a total of 50 COVID-19 patients including seven brought to the hospital from nearby France. Eleven severely ill COVID patients have been placed on ECMO. 

Dr. Lepper first addressed the question of whether COVID-19 acute respiratory syndrome (ARDS) patients should be managed differently from patients with community-based (pneumonia) ARDS. He advised that all patients should be managed according to best practices and what is necessary according to their individual physiology. Using a case example of a 60-year-old man, he delineated each of the parameters used to assess state-of-the-art, protective mechanical ventilation and compared COVID-19 patient measurement parameters versus parameters (CO, PVR, D-Dimers, PEEP, fibrinogen etc.) used to assess usual ARDS patients. He concluded that pulmonary hemodynamics are not profoundly altered in COVID-19 ARDS patients compared to other ARDS patients.

Citing various studies Dr. Lepper then addressed a plethora of subjects including the relevance of driving pressure, the survivor benefits of prone positioning, the use of pulmonary artery catheters (PAC) at his hospital to monitor for right heart failure, early tracheotomies to reduce the use of opioids, and the difficulty with neuromuscular blockers.

After listing the guidelines of Extracorporeal Life Support Organization (ELSO), the European Network of Mechanical Ventilation, and the results of the CESAR and EOLIA trials, and despite a contrary early report by Henry in a Critical Care Journal¹, Dr. Lepper asserted, “I’m a believer. I find that ECMO works in these patients.” He offered the following easily achievable not COVID-19 specific recommendations for managing COVID-19 patients on ECMO: 

• Reduce respiratory rate on ventilator to < 12 minutes
• Reduce patients’ breathing efforts
• Reduce plateau Pressure to reduce ∆P to < 14
• Reduce F1O2 to 0.6 or less; maintain SpO2 < 88% (DO2)
• Adjust PEEP and monitor right heart failure
• Increase inspiratory T to increase mean airway pressure
• Consider prone position on ECMO good thing
• Wean the patient from ECMO as soon as possible

He concluded his talk by stating that COVID-19 seems to be a slowly resolving problem and, in contrast to early reports, ECMO might be a good treatment for COVID-19 patients. ECMO can facilitate ultra-protective ventilation in patients with severe ARDS, especially by reducing the need for ventilation, but this advantage must be protected against the adverse effects of ECMO (thrombosis in both patients and ECMO circuit, bleeding etc.). Finally, hemodynamic monitoring might help guide decisions in patients with severe ARDS.

Following Dr. Lepper’s presentation, he was asked what he meant by advocating an “early” tracheotomy. He replied that the mean at his institution is day seven on ECMO. To a question about driving pressures, Dr. Lepper noted that recruitment maneuvers can be dangerous in volume-depleted patients. Also, he advocated again for tracheotomies, and for PAC to monitor the increase in thoracic pressure to reflect heart function. Finally, he advised having the patient in a prone position long enough (12-16 hours) allowing time for its effect to work. 

Maastricht Experience

Rick Hendrix, MSc, Maastricht University Medical Center then spoke about his institution’s experience using VV-ECMO. At the outset of his presentation, he reported that the World Health Organization (WHO) and ELSO have found that 15% of COVID-19 patients have severe disease that manifests with ARDS, septic shock, coagulation dysfunction, and multiple organ failure. There is a 60% mortality rate in this critically ill population of COVID-19 patients. 

Rik said that the major concerns for the management of COVID-19 patients on ECMO are its immunologic and inflammatory effects and the combined effects on coagulation that result in more thrombi in patients and clotting in the ECMO system (oxygenator, cannula, pump). He then related the Maastricht experience with eight patients that they have had on VV-ECMO, to date. They check for clots through visual inspection and pressure drops and also use the ELSA Monitor to trend graphs of pressure and OXBV because pressure drop alone is not quantitative. 

Rik concluded that it is good to use ECMO to support patients with severe COVID-19 disease, but one must pay close attention to bleeding complications in patients and clotting problems in the patient and/or ECMO system.

When Rik was asked about the specifics on knowing when to change out the system or the oxygenator, he replied that the decision is currently very subjective, but they hope to use the ELSA Monitor to establish quantitative thresholds.

UZ Leuven Experience

The third and final speaker was Kenny van Zwam, a certified perfusionist from UZ Leuven, Belgium, who spoke about the clinical tools used to detect thrombi formation in oxygenators during ECMO-therapy. He noted that visual inspection of an oxygenator can only partially detect clots and that he had wanted to validate the various clinical tools. To do this, they evaluated five parameters (ultrasound dilution technique [UDT], plasma free hemoglobin [PFHb], Fibrinogen, D-dimers, ∆ P) in six patients and found that UDT and D-dimers would rise slowly over time as clots formed, but the other parameters remained the same. They learned that D-dimers could not distinguish small emboli in the bloodstreams of COVID-19 patients so they focused on the use of ultrasound dilution technique and tried to reproduce Krivitski’s validation² with clinical cases. They compared UDT results with the results of a CT scan sliced into 1200 slides and found only a moderate correlation between the CT scan and UDT because CT was not able to detect all small emboli.³ 

Kenny concluded that detection of thrombi formation inside an oxygenator during ECMO therapy is challenging, but the use of new monitoring techniques such as UDT is promising. He cautioned that data is needed to show its sensitivity and specificity.

Before conclusion of the webinar, the three presenters were questioned about what oxygenators and pumps they use and how they know whether to change out only the oxygenator or the whole system. They replied that during this COVID-19 crisis, they are using everything available in the market and strongly advised that a multi-disciplinary team must make decisions about circuit or oxygenator change-outs.

Certification

The American Board of Cardiovascular Perfusion (ABCP) has agreed to award 1.2 credits for attending this webinar and The European Board of Cardiovascular Perfusion (EBCP) has agreed to award one credit to perfusionists that attend the webinar. For more information, go to:

https://info.transonic.com/webinar/ecmo-oxygenatorclotting-video

References:

1. Henry BM. “COVID-19, ECMO, and lymphopenia: a word of caution,” Lancet Respir Med. 2020 Apr;8(4):e24. 
2. Krivitski N, Galyanov G, Cooper D, Said MM, Rivera O, Mikesell GT, Rais-Bahrami K, “In vitro and in vivo assessment of oxygenator blood volume for the prediction of clot formation in an ECMO circuit (theory and validation),” Perfusion. 2018 May;33(1_suppl):51-56. 

B Beely BM, Campbell JE, Meyer A, Langer T, Negaard K, Chung KK, Cap AP, Cancio LC, Batchinsky AI, “Electron Microscopy as a Tool for Assessment of Anticoagulation Strategies During Extracorporeal Life Support: The Proof Is on the Membrane,” ASAIO J. 2016 Sep-Oct;62(5):525-32.