In the ASAIO Journal this year, Dr. Seiler et al.1 from Saarland University Medical Center, Homburg, Germany, present their series of patients from more than a 2-year period that underwent extracorporeal carbon dioxide removal (ECCO2R) via a miniaturized veno-venous blood circuit. Their findings are exciting for the advancement of the field and yield many points of discussion, in support and question.
Extracorporeal life support (ECLS) has been evolving since the late 1970s2 and has gone from bulky, somewhat dangerous diffusion oxygenators and roller pumps to our current state of centrifugal blood pumps and hollow fiber, polymethylpentene oxygenators. The smaller profile pumps with a more favorable impact on the erythrocyte and the coagulation system have enabled further expansion. As the technology continues to improve, and the adverse events lessen, the role of ECLS will continue to expand and further enhance our patients’ lives.3
Seiler et al.1 use a single-site veno-venous ECCO2R circuit via a right internal jugular vein approach. This single site approach4,5 has benefits of improved ambulation and has shown promise in the setting of hypercapnic respiratory failure.5
The Homburg lung employs a pediatric hollow-fiber oxygenator (Quadrox-iD pediatric, Maquet, Rastatt, Germany). These oxygenators have a robust clinical history with minimal pressure drop and allow for a favorable anticoagulation profile. The amount of priming volume is minimal, and for the purposes of ECCO2R, the blood flow rate for effective CO2 removal is relatively minimal. This is advantageous because the blood trauma is minimized and enables the use of a smaller caliber cannula. The access that is able to be used in this series is a 19Fr/21 cm bilumen cannula (Avalon Elite, Maquet, Rastatt, Germany). The 19Fr system is ≈6 mm in diameter and is only slightly larger than a typical hemodialysis catheter. The authors only place the cannula in the superior vena cava/upper right atrium, which minimized the concern for needing to place the Avalon in the inferior vena cava and the potential risk of perforation. With this “high” placement, which is only needed for the ECCO2R, the need for echocardiographic or fluoroscopy guidance during introduction is removed.
The circuit is small and modular, commercially available. This is advantageous in allowing for early mobilization of the hypercapnic patient. The ability to ambulate the patient allows for less debilitation during the critical illness period and may facilitate recovery. The authors advocate a low partial thromboplastin time goal of 50–60 seconds. Their data would support favorable outcomes in terms of catastrophic thrombosis, although the incidence of hemolysis was high.
The approach to the ECCO2R allows for effective CO2 removal in a very ill and complex patient population. As they are able to demonstrate, the use of a miniaturized ECCO2R circuit for hypercapnic respiratory failure, particularly chronic obstructive pulmonary disease (COPD), is effective.
Although the Homburg group has presented compelling data, the widespread application of the ECCO2R approach to hypercapnic respiratory failure is not completely ready for “prime-time.” In the majority of cases, particularly in the COPD patient,6 ventilator management is sufficient to address the disease, and noninvasive ventilation and even home ventilators are becoming routine. The management of these patients long term is the key. Although the current data is compelling for an acute setting of hypercapnic respiratory failure in COPD patients, the long-term impact on their outcomes is unknown, although that question is beyond the scope of the current manuscript.
The venous access is small, the introduction of an ≈6 mm cannula is not a completely benign event. In their small series of 24 patients, there were 2 significant access issues (arrhythmia and air embolism). The acuity of the patients that the group describes is quite high, and they are commended for their high quality, and the invasive nature of any procedure such as this cannot be minimized too much.
The circuit is miniaturized and does have a small priming volume, and the overall footprint is not small. The cart, pump head controller, and the heater–cooler are the typical size for an ECLS circuit. Although it is mobile and smaller than the version in the preceding decades, it is not to the point where it could be patient mounted/carried and enable complete ease of access.
The anticoagulation goal used was reasonable, although the need for anticoagulation cannot be removed. The incidence of hemolysis was extremely high at 87.5%, and the “pathologic” hemolysis was 37.5%. The “pathologic” hemolysis was not well defined, and the name would imply that this was a significant adverse event to the patients. This elevated lactate dehydrogenase and hemolysis does demonstrate that although the bleeding complications may be low, the impact on the erythrocyte and the clotting cascade is not minimal. The goal flow rates of up to 1.5 liters per minute may be too high for minimal impact on the blood.
The ECCO2R system and approach used had very favorable outcomes in terms of the COPD patient; the overall outcomes also need to be put in context. There were 8/24 (33.3%) in-hospital deaths and 8/24 (33.3%) of patients who needed secondary full ECLS. Of those patients who needed additional support with the ECLS, 6/8 (75%) died in the hospital. We do not have the data on the 30 day mortality. The ECCO2R approach did have favorable results in the COPD patients, but the mortality in the non-COPD patients and the high mortality rate in the patients who progress to needing full ECLS should give a moment of pause. No doubt these patients are extremely ill and without many additional therapies available, but their high morbidity and mortality could cause one to reflect on the overall benefit of a resource-intensive therapy in these settings especially if there is progression to needing full ECLS.
Seiler et al.1 demonstrate that a miniaturized ECCO2R circuit is effective in removing carbon dioxide in hypercapnic respiratory failure. The impact on those patients with COPD appears to be quite favorable. The overall patient population is quite ill with multiple comorbidities, and the severity of their illnesses does not have many effective treatment options. The single-site approach to ECCO2R with a mobile circuit allows for enhanced mobility with minimal access complications and will undoubtedly have an expanding role in the treatment of selected patients with respiratory collapse.
1. Seiler F, Trudzinski R, Hennemann K, et al. The Homburg lung - efficacy and safety of a minimally-invasive pump-driven device for veno-venous extracorporeal carbon dioxide removal. ASAIO J 2017.63:659–665.
2. Gattinoni L, Kolobow T, Tomlinson T, White D, Pierce J. Control of intermittent positive pressure breathing (IPPB) by extracorporeal removal of carbon dioxide. Br J Anaesth 1978.50: 753–758.
3. Agerstrand CL, Bacchetta MD, Brodie D. ECMO for adult respiratory failure: current use and evolving applications. ASAIO J 2014.60: 255–262.
4. Redwan B, Ziegeler S, Semik M, Fichter J, Dickgreber N, Vieth V, et al. Single-site cannulation venovenous extracorporeal CO2 removal as bridge to lung volume reduction surgery in end-stage lung emphysema. ASAIO J. 2016.62(6): 743–746.
5. Malik M, Kilic A, Whitson BA. Percutaneous single-site cannulation for acute right sided support. ASAIO J 2017. doi: 10.1097/MAT.0000000000000556. [Epub ahead of print].
6. Bergin SP, Rackley CR. Managing respiratory failure in obstructive lung disease. Clin Chest Med 2016.37: 659–667.