Toward Understanding Cerebral Blood Flow during Cardiopulmonary Bypass: Implications for the Central Nervous System

Area of Science:

• Cardiovascular Surgery
• Neuroscience
• Physiology

Background:

• Cardiopulmonary bypass (CPB) is a critical procedure in cardiac surgery.
• Understanding factors affecting cerebral blood flow (CBF) during CPB is vital for patient outcomes.
• Hypothermic CPB is commonly employed, but its effects on cerebral perfusion require investigation.

Purpose of the Study:

• To investigate the relationship between regional cerebral blood flow (CBF) and various physiological parameters during nonpulsatile hypothermic cardiopulmonary bypass (CPB).
• To identify the significant factors influencing CBF during CPB.
• To assess the integrity of cerebral autoregulation under CPB conditions.

Main Methods:

• Regional CBF was measured using xenon 133 clearance in 67 patients undergoing coronary bypass grafting.
• Data were collected on mean arterial pressure, systemic blood flow, PaCO2, nasopharyngeal temperature, and hemoglobin.
• A subgroup analysis examined the effect of varying pump flow rates (1.0–2.0 L/min/m²).

Main Results:

• A significant 55% decrease in regional CBF was observed during CPB.
• Nasopharyngeal temperature and PaCO2 were identified as the only statistically significant factors affecting CBF (p < 0.05).
• Variations in pump flow within the tested range did not significantly impact regional CBF in a subgroup of patients.

Conclusions:

• Cerebral autoregulation is preserved during hypothermic nonpulsatile CPB.
• Under typical CPB conditions, fluctuations in blood flow and pressure do not appear to cause significant physiological or clinical adverse effects.
• Maintaining appropriate nasopharyngeal temperature and PaCO2 are crucial for optimizing CBF during CPB.