Extracorporeal carbon dioxide removal with continuous renal replacement therapy. Case description and literature review

[Recent research on extracorporeal carbon dioxide removal]

Extracorporeal carbon dioxide removal is an artificial lung auxiliary technique based on extrapulmonary gas exchange and can effectively remove carbon dioxide and provide oxygenation to a certain extent, and it is one of the effective treatment techniques for hypercapnia developed after mechanical ventilation and extracorporeal membrane oxygenation in recent years and has wide application prospect. This article elaborates on the development, working principle, advantages, classification, complications, and clinical application of extracorporeal carbon dioxide removal, so as to provide a new choice for extracorporeal carbon dioxide removal in clinical practice.

Trends, Advantages and Disadvantages in Combined Extracorporeal Lung and Kidney Support From a Technical Point of View

Extracorporeal membrane oxygenation (ECMO) provides pulmonary and/or cardiac support for critically ill patients. Due to their diseases, they are at high risk of developing acute kidney injury. In that case, continuous renal replacement therapy (CRRT) is applied to provide renal support and fluid management. The ECMO and CRRT circuits can be combined by an integrated or parallel approach. So far, all methods used for combined extracorporeal lung and kidney support present serious drawbacks. This includes not only high risks of circuit related complications such as bleeding, thrombus formation, and hemolysis, but also increase in technical workload and health care costs. In this sense, the development of a novel optimized artificial lung device with integrated renal support could offer important treatment benefits. Therefore, we conducted a review to provide technical background on existing techniques for extracorporeal lung and kidney support and give insight on important aspects to be addressed in the development of this novel highly integrated artificial lung device.

Modeling acid-base balance for in-series extracorporeal carbon dioxide removal and continuous venovenous hemofiltration devices

Patients with acute respiratory distress syndrome and acute kidney injury (AKI) treated by kidney replacement therapy may also require treatment with extracorporeal carbon dioxide removal (ECCO₂ R) devices to permit protective or ultraprotective mechanical ventilation. We developed a mathematical model of acid-base balance during extracorporeal therapy using ECCO₂ R and continuous venovenous hemofiltration (CVVH) devices applied in series for the treatment of mechanically ventilated AKI patients. Published data from clinical studies of mechanically ventilated AKI patients treated by CVVH at known infusion rates of substitution fluid without ECCO₂ R were used to adjust the model parameters to fit plasma levels of arterial partial pressure of carbon dioxide (PaCO₂ ), arterial plasma bicarbonate concentration ([HCO₃ ]), and plasma pH (as well as certain other unmeasured physiological variables). The effects of applying ECCO₂ R at an unchanged and a reduced tidal volume on PaCO₂ , [HCO₃ ] and plasma pH were then simulated assuming carbon dioxide removal rates from the ECCO₂ R device measured in the clinical studies. Agreement of such model predictions with clinical data was good whether the ECCO₂ R device was positioned proximal or distal to the CVVH device in the extracorporeal circuit. Although carbon dioxide removal rates from the ECCO₂ R device measured in one previous clinical study were higher when it was placed proximal to the CVVH device, suggesting that such in-series positioning was optimal, the current mathematical model demonstrates that proximal positioning of the ECCO₂ R device also results in lower bicarbonate (and, therefore, total carbon dioxide) removal from the distal CVVH device. Thus, the removal of total carbon dioxide by such extracorporeal circuits is relatively independent of the position of the in-series devices. It is concluded that the described mathematical model has quantitative accuracy; these results suggest that the overall acid-base balance when using ECCO₂ R and CVVH devices in a single extracorporeal circuit will be similar, independent of their in-series position.

Continuous renal replacement therapy and extended indications

Extracorporeal blood purification (EBP) techniques provide support for critically ill patients with single or multiple organ dysfunction. Continuous renal replacement therapy (CRRT) is the modality of choice for kidney support for those patients and orchestrates the interactions between the different artificial organ support systems. Intensive care teams should be familiar with the concept of sequential extracorporeal therapy and plan on how to incorporate new treatment modalities into their daily practices. Importantly, scientific evidence should guide the decision-making process at the bedside and provide robust arguments to justify the costs of implementing new EBP treatments. In this narrative review, we explore the extended indications for CRRT as an adjunctive treatment to provide support for the heart, lung, liver, and immune system. We detail practicalities on how to run the treatments and how to tackle the most frequent complications regarding each of the therapies, whether applied alone or integrated. The physicochemical processes and technologies involved at the molecular level encompassing the interactions between the molecules, membranes, and resins are spotlighted. A clinical case will illustrate the timing for the initiation, maintenance, and discontinuation of EBP techniques.