Extracorporeal membrane oxygenation using a centrifugal pump and a servo regulator to prevent negative inlet pressure

Background. We studied whether negative inlet pressure created by a centrifugal pump during extracorporeal membrane oxygenation damages blood. Methods. Fresh, whole human blood and primer were circulated through a test circuit, applying an inlet pressure of 0, −50, or −100 mm Hg. Thereafter, hemolysis and kidney function were compared between 6 patients treated before and 14 patients treated after inclusion in our setup of extracorporeal membrane oxygenation with a servo inlet pressure regulator. Results. In vitro, negative inlet pressure caused substantial hemolysis, leukocyte and platelet destruction, and complement activation. Maximal plasma free hemoglobin concentrations were 199 mg/100 mL before use of the servo inlet pressure regulator and 40 mg/100 mL afterward (p = 0.06), and serum creatinine peaked at 330 and 115 μmol/L, respectively (p = 0.03). The minimal 24-hour diuresis normalized for weight was 4.8 mL/kg before use of the servo inlet pressure regulator and 45.6 mL/kg afterward (p = 0.03). Three of 5 evaluable patients before use of the servo inlet pressure regulator and 1 of 14 patients after inclusion in this setup experienced anuria (p = 0.04). Conclusions. There were strong indications that reduction of negative pump inlet pressure with the servo regulator prevented hemolysis and kidney damage.