A new type of low blood flow ECCO2R using a hemodialysis system in apneic states

To perform low blood flow extracorporeal CO2 removal (ECCO2R), the authors developed a device for extracorporeal circulation (ECC) equipped with a dialyzer for the elimination of CO2 as bicarbonate. The major problem with this method was the decrease in blood pH. To control blood pH and clarify the limit of CO2 elimination using this method, a study with apneic dogs was performed. Six anesthetized mongrel dogs were intubated and paralyzed with a muscle relaxant. Vascular access was achieved with a venovenous bypass. ECC was initiated under apneic oxygenation (100% O2, 10 cm H2O continuous airway pressure), and the CO2 concentration in the airway outlet was measured. The CO2 was converted to bicarbonate using systemic infusion of trihydroxy-methylamino methane (THAM), and the generated bicarbonate was removed by hemodialysis. Blood flow rate in the ECC was 15 ml/kg/min, and the duration of ECC was 5 hr. During ECC, the hemodynamic parameters of the dogs were stable, and the PaCO2 remained at about 90 mmHg with a PaO2 above 350 mmHg; CO2 elimination from the airway was negligible.