Twelve hours in vitro biocompatibility testing of membrane oxygenators

In vitro test systems for extracorporeal membrane oxygenation (mock loop) represent an interesting alternative to complex and expensive in vivo test systems to analyze the pathomechanisms leading to insufficient biocompatibility. Data on mock loop systems are limited, and operation times are constricted to a maximum duration of 6 hr. This study aims at a 12 hr operation time and frequent monitoring of markers for insufficient biocompatibility in two experimental settings. Porcine blood circulated in a mock loop without any modifications, or the circuit was operated with a CO ₂ -enhanced gas (5% CO ₂ /21% O ₂ /74% N ₂ ) in combination with a nutrient solution (phosphate-adenine-glucose-guanosine-saline-mannitol). Coagulation parameters changed over time without differences between the two groups. In the unmodified test setting, a pH increase was detected after 1 hr, followed by significantly increased levels of free hemoglobin as a marker for hemolysis and elevated numbers of activated platelets, which correlate with detected von Willebrand factor, microparticles, and interleukin-β. Proinflammatory cytokine levels were significantly increased after 12 hr. In contrast, these parameters remained constant in the modified test setting providing proof of a stable operating in vitro mock loop system with an extended/prolonged operation time.