Minimal-flow ECCO₂R in patients needing CRRT does not facilitate lung-protective ventilation

Extracorporeal CO₂ removal (ECCO₂R) is intended to facilitate lung protective ventilation in patients with hypercarbia. The combination of continuous renal replacement therapy (CRRT) and minimal-flow ECCO₂R offers a promising concept for patients in need of both. We hypothecated that this system is able to remove enough CO₂ to facilitate lung protective ventilation in mechanically ventilated patients. In 11 ventilated patients with acute renal failure who received either pre- or postdilution CRRT, minimal-flow ECCO₂R was added to the circuit. During 6 h of combined therapy, CO₂ removal and its effect on facilitation of lung-protective mechanical ventilation were assessed. Ventilatory settings were kept in assisted or pressure-controlled mode allowing spontaneous breathing. With minimal-flow ECCO₂R significant decreases in minute ventilation, tidal volume and paCO₂ were found after one and three but not after 6 h of therapy. Nevertheless, no significant reduction in applied force was found at any time during combined therapy. CO₂ removal was 20.73 ml CO₂/min and comparable between pre- and postdilution CRRT. Minimal-flow ECCO₂R in combination with CRRT is sufficient to reduce surrogates for lung-protective mechanical ventilation but was not sufficient to significantly reduce force applied to the lung. Causative might be the absolute amount of CO₂ removal of only about 10% of resting CO₂ production in an adult as we found. The benefit of applying minimal flow ECCO₂R in an uncontrolled setting of mechanical ventilation might be limited.