Update on extracorporeal carbon dioxide removal: a comprehensive review on principles, indications, efficiency, and complications

Abstract

Technology: Extracorporeal carbon dioxide removal means the removal of carbon dioxide from the blood across a gas exchange membrane without substantially improving oxygenation. Carbon dioxide removal is possible with substantially less extracorporeal blood flow than needed for oxygenation. Techniques for extracorporeal carbon dioxide removal include (1) pumpless arterio-venous circuits, (2) low-flow venovenous circuits based on the technology of continuous renal replacement therapy, and (3) venovenous circuits based on extracorporeal membrane oxygenation technology. Indications: Extracorporeal carbon dioxide removal has been shown to enable more protective ventilation in acute respiratory distress syndrome patients, even beyond the so-called “protective” level. Although experimental data suggest a benefit on ventilator induced lung injury, no hard clinical evidence with respect to improved outcome exists. In addition, extracorporeal carbon dioxide removal is a tool to avoid intubation and mechanical ventilation in patients with acute exacerbated chronic obstructive pulmonary disease failing non-invasive ventilation. This concept has been shown to be effective in 56-90% of patients. Extracorporeal carbon dioxide removal has also been used in ventilated patients with hypercapnic respiratory failure to correct acidosis, unload respiratory muscle burden, and facilitate weaning. In patients suffering from terminal fibrosis awaiting lung transplantation, extracorporeal carbon dioxide removal is able to correct acidosis and enable spontaneous breathing during bridging. Keeping these patients awake, ambulatory, and breathing spontaneously is associated with favorable outcome. Complications: Complications of extracorporeal carbon dioxide removal are mostly associated with vascular access and deranged hemostasis leading to bleeding. Although the spectrum of complications may differ, no technology offers advantages with respect to rate and severity of complications. So called “high-extraction systems” working with higher blood flows and larger membranes may be more effective with respect to clinical goals.

A bi‐centric experience of extracorporeal carbon dioxide removal (ECCO2R) for acute hypercapnic respiratory failure following allogeneic hematopoietic stem cell transplantation

“…Complications attributable to ECCO 2 R may vary between different carbon dioxide removers, configurations, and devices. 6 Due to substantial heterogeneity in these aspects and the small sample size, our study could not specifically address this critical issue. When interpreting the complications observed in our cohort and other reports, the used devices and methodology should be considered before making broad interferences about the risks and benefits of ECCO 2 R other than those related to the patient type.…”

Extracorporeal CO2 removal and renal replacement therapy in acute severe respiratory failure in COVID‐19 pneumonia: Case report

“…CO 2 extracorporeal removal systems, both the extracorporeal membrane oxygenation (ECMO) and ECCO 2 R, are useful in multiple clinical scenarios, but in ARDS the ECCO 2 R should be considered in cases of pH<7.25, PaCO 2 >65 mmHg, and PaO 2 /FiO 2 >80 4 . The decision of ECCO 2 R coupled with CVVHD depends on the need renal support and the availability of trained nursing staff.…”

“…The ECCO 2 R are partial low‐flow respiratory support systems that can be implemented with membranes of different surfaces (0.33 to 1.81 m 2 ) and allows extraction of 25% of the CO 2 content in the blood, reducing ventilatory requirements 4,13 . The CO 2 diffusion capacity is 20 times greater than oxygen, which allows the system to purify CO 2 at low flows of blood (Qb <500 ml/min).…”

“…The ECCO 2 R allows to reduce the ventilatory demand, decrease Vt to 3–4 ml/kg of ideal weight and to keep plateau pressures less than 25 cmH 2 O and driving pressures of less than 15 cmH 2 O allowing ultra protective MV in a safe way, with less risk of hemorrhagic complications related to the vascular access, lower costs, less technical difficulties with less need of trained staff. ECMO system is a more complex technique, requires greater blood flows and bigger vascular cannulas (21 to 31 Fr) 4 …”

“…That clinical practice has demonstrated to improve survival in patients with respiratory distress syndrome (ARDS) 1,2 . However, an undesirable consequence of protective MV is hypoventilation and hypercapnia, 3 acute pulmonary hypertension, diminished myocardial contractility, reduced renal blood flow, and release of endogenous catecholamins 4 . Hypercapnic acidosis associates to increase hospital mortality, prolonged hospital stay, and a reduction in survival with PaCO 2 greater than 65 mmHg 5 .…”