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Complement activation before, during and after cardiopulmonary bypass
1Department of Surgery, Brompton Hospital, London, UK.
Insights
Heparin administration before cardiopulmonary bypass may activate the complement cascade. This study found complement activation during bypass, suggesting both classical and alternative pathway involvement.
Area of Science:
- Immunology
- Cardiovascular Surgery
Background:
- The complement system plays a crucial role in innate immunity.
- Cardiopulmonary bypass (CPB) is known to activate the complement system.
- Understanding complement activation during CPB is vital for patient outcomes.
Purpose of the Study:
- To investigate complement activation pathways during CPB for coronary artery surgery.
- To determine the role of heparin in initiating complement activation.
Main Methods:
- Measured plasma levels of complement components (C3, C4, factor B) and split products (C3d, C4d, Ba) in 12 patients.
- Analyzed complement pathway activation through component levels and ratios before and during CPB.
Main Results:
- Significant increases in Ba and C3d levels and Ba:B and C3d:C3 ratios were observed after heparin administration, preceding CPB.
- During CPB, significant depletion of complement components and elevation of split products indicated activation of both classical and alternative pathways.
- Statistical significance was noted for key markers (P < 0.05 and P < 0.01).
Conclusions:
- Heparin administration may initiate alternative complement pathway activation.
- Both classical and alternative complement pathways are activated during CPB.
- This study elucidates complement activation during CPB and highlights heparin's potential role.
Abstract:
Plasma levels of the complement parent molecules C3, C4, and factor B and their split products, C3d, C4d, and Ba were measured in 12 patients undergoing cardiopulmonary bypass for coronary artery surgery. Alternative and common complement pathway activation, demonstrated by statistically significant rising levels of Ba (P less than 0.05), and C3d (P less than 0.05) and by elevated Ba:B (P less than 0.05) and C3d:C3 (P less than 0.05) ratios were found before the institution of cardiopulmonary bypass but following heparin administration suggesting that heparin may itself initiate alternative pathway activation. In addition, significant depletion of parent complement components and elevation of split product concentrations was seen during bypass suggesting classical and alternate pathway activation (P less than 0.01). This study clarifies the pathways of complement activation during bypass and presents evidence that heparin administration may initially activate the complement cascade.