[A study on complement activation in cardiopulmonary bypass--experimental and clinical evaluations]

Area of Science:

• Immunology
• Cardiovascular Surgery
• Biomaterials

Background:

• Complement activation is a significant concern during cardiopulmonary bypass (CPB).
• Different oxygenator types may influence the degree of complement activation.
• Anaphylatoxins are key indicators of complement system activation.

Purpose of the Study:

• To compare complement activation, specifically anaphylatoxins, between bubble and membrane oxygenators during CPB.
• To investigate the role of primed homologous blood and blood trauma in complement activation.
• To elucidate the pathways (classical vs. alternative) involved in complement activation during CPB.

Main Methods:

• Measured complement levels (C4a, C3a, C5a) in patients undergoing CPB with bubble (BOG) versus membrane (MOG) oxygenators.
• Evaluated the influence of the homologous to autologous blood volume ratio (H/A ratio).
• Conducted experiments in monkeys (Macaca fascicularis) with extracorporeal blood exposure to oxygen, nylon, or microbubbles.

Main Results:

• Bubble oxygenator group (BOG) showed increased C4a and C3a levels compared to the membrane oxygenator group (MOG).
• Higher H/A ratios in the BOG correlated with a marked initial rise in C4a levels.
• Monkey studies indicated elevated C4a and C3a with bubbled blood, and C3a with nylon contact, but not with microbubbles.

Conclusions:

• CPB via bubble oxygenators triggers more complement activation, potentially via the classical pathway, than membrane oxygenators.
• Blood trauma and plasma denaturation appear to contribute to higher anaphylatoxin levels in the BOG.
• The H/A ratio is a significant factor modulating complement activation during CPB.