Background: Cerebral damage is a major problem after reconstructive surgery of the aortic arch and the descending aorta. Current protective strategies, including deep hypothermia and antegrade cerebral perfusion (ACP), are used to prolong the tolerated duration of circulatory arrest. The aim of the study was to observe the influence of deep hypothermic circulatory arrest (DHCA) and ACP on neuronal apoptosis in the hippocampus. To further elucidate the mechanisms of neurologic injury and protection, we assessed the expression of the antiapoptotic protein Bcl-2 and the proapoptotic protein Bax.
Methods: We randomly divided 18 pigs into 3 groups: The control group (n = 6) received normal-temperature cardiopulmonary bypass (CPB), the DHCA group (core temperature, 18 degrees C; n = 6) received DHCA for 90 minutes, and the third group (DHCA + ACP) (core temperature, 18 degrees C; ACP, flow rate of 30 mL/kg per minute at a pressure of 15-25 mm Hg; n = 6) received DHCA for 90 minutes. Hippocampal tissue was sampled 2 hours after CPB was finished. Bcl-2 and Bax expression was examined by immunohistochemistry. Morphologic changes in hippocampal tissue were measured with transmission electron microscopy.
Results: Bax protein levels were significantly higher in the DHCA group than in the other 2 groups (P < .05), whereas Bcl-2 protein levels were significantly higher in the DHCA + ACP group than in the other 2 groups (P < .05). Obvious neuronal apoptosis was observed in the DHCA group but not in the controls, and few apoptotic neurons were seen in the DHCA + ACP group.
Conclusions: DHCA can induce neuronal apoptosis in the hippocampus. ACP during the DHCA period protects cerebral tissue by suppressing apoptosis through decreasing Bax expression and increasing Bcl-2 expression.