Optimal brain temperature for retrograde cerebral perfusion in dogs

Abstract

We investigated the optimal brain temperature during the period of retrograde cerebral perfusion (RCP). Eighteen mongrel dogs were divided into three groups according to brain temperatures during the period of RCP: L (15°C), M (20°C), and H (25°C). Following hypothermia using cardiopulmonary bypass (CPB), RCP was performed for 60 minutes via the bilateral internal maxillary veins with a perfusion pressure of 25 mmHg. The animals were then rewarmed for 60 minutes. Cerebral blood flow (CBF) was measured by laser Doppler flowmetry. The cerebral metabolic rate for oxygen (CMRO₂) and glucose (CMRGlu), excretion of carbon dioxide (ExCO₂), and lactate/pyruvate (L/P) ratio were calculated. During the period of RCP, brain temperature significantly (p < 0.05) increased in Group L. CBF, CMRO₂, ExCO₂, and CMRGlu significantly (p < 0.05) decreased to less than 20% of the baseline levels during the period of RCP in all groups. After RCP, CBF recovered noticeably beyond the baseline levels in Group M (130%). CMRO₂ and ExCO₂ levels in Groups M and H tended to be higher than those in Group L during the rewarming phase. Increase of CMRGlu immediately after RCP was higher in Group M compared with other groups. The L/P ratio in Group M was lower than that in the other two groups during RCP. In conclusion, the brain temperature in the range 20°C may be suitable for maintaining optimal cerebral metabolic activity for RCP.