The effect of air exposure on leucocyte and cytokine activation in an in-vitro model of cardiotomy suction

Cardiopulmonary bypass (CPB) is known to cause a systemic inflammatory and immune response.

An in-vitro model of cardiotomy suction was designed to quantify the effects of incrementally increased air-blood exposure on leucocyte marker CD11b and cytokine activation in two common anticoagulants, heparin and citrate.

Fresh human blood was exposed to increasing amounts of air flow for ten minutes. Leucocyte and cytokine levels were measured prior to and after ten minutes of air flow. Cytokine levels were also measured after air exposure when incubated for 24 hours at 37^oC.

Leucocyte activation, measured by CD11b, was elevated between baseline and air flow rates up to 50 mL/min. After 10 minutes of air exposure, no measured cytokine levels were elevated. After 24 hours of incubation, cytokine levels of TNFα, IL-10, IL-6, and IL-8 were elevated. However, only IL-8 was significantly elevated in citrated blood, but not in heparinized blood, when compared to baseline samples that were also incubated for 24 hours.

This study investigates CD11b levels in response to an air stimulus in blood that was anticoagulated with citrate or heparin. Exposure to an air stimulus activates leucocytes. Activation of CD11b was less when using heparin as an anticoagulant compared to citrate. Cytokine activation occurs with air stimulation, but levels do not immediately rise, indicating that time is required to generate free cytokines.