Cardiopulmonary bypass: studies on its damaging effects

Area of Science:

• Cardiovascular Surgery
• Physiology
• Biomedical Engineering

Background:

• Cardiopulmonary bypass (CPB) is essential for cardiac surgery but induces a pathologic inflammatory state.
• CPB activates complement, coagulation, kallikrein, and fibrinolytic cascades, causing systemic inflammation.
• Significant changes in organ perfusion and metabolism occur during CPB, influenced by flow rates.

Purpose of the Study:

• To investigate the effects of CPB on microcirculation and inflammatory responses.
• To understand how perfusion flow rates impact organ perfusion during CPB.
• To identify strategies for improving the safety of CPB.

Main Methods:

• Review of existing literature on CPB-induced inflammation and microcirculatory changes.
• Analysis of experimental studies on hypothermic and normothermic CPB effects.
• Examination of ultrafiltration data regarding microvascular permeability.

Main Results:

• Hypothermic CPB (20°C) at flow rates <1.2 L/min/m² reduces microcirculatory perfusion.
• Brain oxygen consumption and resistance remain stable with reduced flow during hypothermia, increasing relative brain blood flow.
• Normothermic CPB for 2 hours increases microvascular permeability to proteins, leading to interstitial fluid accumulation.

Conclusions:

• CPB triggers a generalized inflammatory response and alters microcirculation.
• Perfusion flow rate critically affects organ perfusion, particularly microcirculation, during CPB.
• Enhancing CPB safety requires preventing microcirculatory dysfunction and mitigating inflammatory mediator effects.