Selective cerebral perfusion: real-time evidence of brain oxygen and energy metabolism preservation

Abstract

Background: Deep hypothermic circulatory arrest (DHCA) is commonly used for complex cardiac operations in children, often with selective cerebral perfusion (SCP). Little data exist concerning the real-time effects of DHCA with or without SCP on cerebral metabolism. Our objective was to better define these effects, focusing on brain oxygenation and energy metabolism.

Methods: Piglets undergoing cardiopulmonary bypass were assigned to either 60 minutes of DHCA at 18 degrees C (n = 9) or DHCA with SCP at 18 degrees C (n = 8), using pH-stat management. SCP was administered at 10 mL/kg/min. A cerebral microdialysis catheter was implanted into the cortex for monitoring of cellular ischemia and energy stores. Cerebral oxygen tension and intracranial pressure also were monitored. After DHCA with or without SCP, animals were recovered for 4 hours off cardiopulmonary bypass.

Results: With SCP, brain oxygen tension was preserved in contrast to DHCA alone (p < 0.01). Deep hypothermic circulatory arrest was associated with marked elevations of lactate (p < 0.01), glycerol (p < 0.01), and the lactate to pyruvate ratio (p < 0.001), as well as profound depletion of the energy substrates glucose (p < 0.001) and pyruvate (p < 0.001). These changes persisted well into recovery. With SCP, no significant cerebral microdialysis changes were observed. A strong correlation was demonstrated between cerebral oxygen levels and cerebral microdialysis markers (p < 0.001).

Conclusions: Selective cerebral perfusion preserves cerebral oxygenation and attenuates derangements in cerebral metabolism associated with DHCA. Cerebral microdialysis provides real-time metabolic feedback that correlates with changes in brain tissue oxygenation. This model enables further study and refinement of strategies aiming to limit brain injury in children requiring complex cardiac operations.