Effect of methylprednisolone on complement activation during heparin neutralization

Area of Science:

• Cardiovascular Surgery
• Immunology
• Pharmacology

Background:

• Steroids are commonly used before cardiopulmonary bypass (CPB) to mitigate "first phase" complement activation.
• The impact of steroid pretreatment on "second phase" complement activation during protamine administration remains unclear.
• Heparin-protamine interaction is known to trigger complement activation post-CPB.

Purpose of the Study:

• To investigate the effect of high-dose methylprednisolone pretreatment on complement activation during heparin-protamine interaction.
• To determine if steroid pretreatment influences "second phase" complement activation after CPB termination.

Main Methods:

• A randomized, placebo-controlled study involving 16 patients undergoing coronary artery bypass graft surgery.
• Eight patients received methylprednisolone (30 mg/kg) pre-CPB (group MP), while eight received placebo (group C).
• Complement components (C3a, C4a, C5a) were measured using radioimmunoassay before and after protamine administration.

Main Results:

• Both groups showed increased C3a and C4a levels post-protamine, indicating complement activation.
• Methylprednisolone-treated patients exhibited significantly lower C3a and C4a levels compared to placebo.
• No significant C5a levels were detected in either group.

Conclusions:

• Methylprednisolone pretreatment effectively inhibits "second phase" complement activation during heparin-protamine interaction.
• The anti-complementary effect of steroid pretreatment extends beyond the CPB period.
• Findings suggest potential benefits for patients at risk of severe anaphylactoid reactions to protamine.