Kidney Dialysis Circuit Doubles as Lung Support in Children With Severe ARDS

When a child’s lungs fail so severely that even a breathing machine set to gentlest settings cannot keep carbon dioxide levels safe, intensive care doctors face a grim dilemma. Push the ventilator harder and risk tearing already inflamed lung tissue; hold back and let acid build up in the blood. A team at the Medical Center – University of Freiburg in Germany has now reported an approach that sidesteps this trade-off by borrowing capacity from a machine many of these children already need anyway: the dialysis circuit used for continuous renal replacement therapy, or CRRT.

The new report, published in BMC Pediatrics, describes a retrospective single-center case series of seven children with pediatric acute respiratory distress syndrome, or PARDS, who also had acute kidney injury. In each case, the clinicians integrated extracorporeal carbon dioxide removal, known as ECCO₂R, into a CRRT circuit that had already been indicated for kidney support. Rather than adding a second large-bore extracorporeal circuit dedicated solely to lung support, the team adapted the existing blood purification circuit so that it could also strip carbon dioxide from the bloodstream. The study was retrospectively registered in the German Clinical Trials Register as DRKS00038799.

The physiological logic behind the technique is straightforward but demanding in practice. ECCO₂R works by passing blood through a gas exchanger, essentially an artificial membrane lung, where a controlled flow of oxygen sweeps carbon dioxide across the membrane and out of the blood. The removed CO₂ is then vented away, and the blood returns to the patient with a lower carbon dioxide tension. Because carbon dioxide diffuses through membranes far more readily than oxygen does, meaningful CO₂ clearance can be achieved at blood flows far lower than those required for full extracorporeal membrane oxygenation, or ECMO. In adults, this has made ECCO₂R attractive as a way to permit ultra-lung-protective ventilation, in which tidal volumes and airway pressures are driven down to minimize ventilator-induced lung injury while the artificial circuit takes over the burden of CO₂ elimination.

In children, however, the technique has remained largely unexplored territory. Pediatric patients have smaller blood volumes, lower cardiac outputs, and narrower vascular access, all of which complicate the extracorporeal circuits designed primarily for adults. The Freiburg team’s insight was that children who need both lung support and kidney support could, in principle, have both delivered through a single circuit. CRRT machines already circulate blood continuously through an extracorporeal loop; adding a gas exchanger in that loop converts the circuit into a dual-purpose organ support system without the need for additional large-bore cannulation.

To assess how this played out in practice, the researchers analyzed the first treatment episode for each of seven patients treated between November 2023 and November 2025, restricting the principal analysis to one episode per patient to avoid the statistical problems that arise when repeated observations from the same child are treated as independent. The children had a median age of 12 years, with an interquartile range of 6 to 14 years. ECCO₂R was delivered at a median blood flow of 270 milliliters per minute, with an interquartile range of 100 to 300 milliliters per minute. That flow corresponds to roughly 9 percent of the estimated cardiac output, with an interquartile range of 6 to 20 percent, a strikingly modest fraction compared with the much higher flows typical of ECMO.

The physiological results, analyzed with Friedman tests for longitudinal change, showed statistically significant improvements across all predefined principal outcomes. Median arterial carbon dioxide tension, or PaCO₂, fell by 10 millimeters of mercury within the first 24 hours, with an interquartile range of −27 to −3 millimeters of mercury. Peak inspiratory pressure dropped by a median of 11 millibars, driving pressure by 9 millibars, and tidal volume by 1.6 milliliters per kilogram of body weight. Each of these shifts points in the direction that lung-protective ventilation strategies aim for: less pressure, less stretch, less stress on injured lung tissue, achieved while carbon dioxide was being cleared extracorporeally rather than by aggressive ventilator settings.

On the safety front, the picture was cautiously reassuring but not unblemished. The investigators found no predefined major bleeding events, no clinically apparent hemolysis, no thromboembolic complications, and no device-related infections attributable to the integrated ECCO₂R-CRRT approach. The main complication observed was circuit clotting requiring circuit exchange, which occurred in two of the seven patients. Four of the seven children were successfully weaned from ECCO₂R during their treatment course. For a first-in-children application of an adapted circuit, these figures suggest that the approach can be delivered without an outsized burden of extracorporeal complications, though the small sample size and retrospective design make it impossible to draw firm conclusions about true event rates.

The authors are careful to frame their findings as hypothesis-generating rather than as evidence of treatment efficacy or device safety. This is a retrospective, uncontrolled, single-center case series with seven patients in the principal analysis, and the observed improvements in PaCO₂ and ventilatory pressures are temporally associated with ECCO₂R initiation rather than causally attributable to it. Children with PARDS and AKI are a heterogeneous group, and natural disease evolution, changes in sedation, adjustments in ventilator strategy, and concurrent therapies could all contribute to the measured changes. Still, the consistency of the physiological signal across multiple outcomes, and the fact that it emerged in a real-world pediatric intensive care setting rather than a highly controlled research protocol, gives the findings practical weight.

The study also highlights the interdisciplinary machinery required to make such an approach work. The authors specifically acknowledge the dialysis nursing team, the Division of Pediatric Nephrology, and the nursing staff of the Pediatric Intensive Care Unit at the Medical Center – University of Freiburg, noting that their expertise and dedication were essential to successful implementation. They also thank the family of the first child treated with integrated ECCO₂R-CRRT at the institution for supporting publication of the experience. The research received no dedicated financial support, with open access funding organized through Projekt DEAL, and the authors declare no competing interests.

Looking ahead, the Freiburg team argues that prospective multicenter studies are needed to define patient selection criteria, anticoagulation strategies, weaning protocols, and the broader role of integrated ECCO₂R-CRRT within pediatric extracorporeal respiratory support. If those questions can be answered, the approach could offer a pragmatic middle ground for carefully selected children who need both kidney and lung support, avoiding the cannulation burden and complexity of full ECMO while still relieving the ventilator of some of its most dangerous demands. For now, the message is one of cautious optimism: a technique borrowed from adult critical care, adapted to the constraints of pediatric physiology and existing dialysis infrastructure, appears technically feasible and physiologically promising in a small, carefully selected cohort.

Subject of Research: Extracorporeal carbon dioxide removal integrated into continuous renal replacement therapy for pediatric acute respiratory distress syndrome

Article Title: Extracorporeal carbon dioxide removal integrated into continuous renal replacement therapy in pediatric patients with ARDS: a retrospective single-center case series

Article References: Kuntz, M., Matheisl, D., Schüle, I., Klotz, D., Fuchs, H., & Schneider, H. (2026). Extracorporeal carbon dioxide removal integrated into continuous renal replacement therapy in pediatric patients with ARDS: a retrospective single-center case series. BMC Pediatrics, 26(1), Article 860. https://doi.org/10.1186/s12887-026-07656-y

Image Credits: AI Generated

DOI: 10.1186/s12887-026-07656-y

Keywords: ECCO2R, continuous renal replacement therapy, pediatric ARDS, acute kidney injury, lung-protective ventilation, pediatric critical care, extracorporeal membrane oxygenation, carbon dioxide removal, case series, pediatric intensive care, ventilator pressures, BMC Pediatrics