Optimized retrograde cerebral perfusion reduces ischemic energy depletion

Area of Science:

• Neuroscience
• Cardiovascular Science
• Biochemistry

Background:

• Retrograde cerebral perfusion (RCP) is known to provide minimal capillary flow, but its capacity for aerobic metabolic support remains unclear.
• Hypothermic circulatory arrest (HCA) is used in clinical settings, necessitating strategies to protect brain metabolism during reduced blood flow.

Purpose of the Study:

• To evaluate if optimizing perfusate composition for RCP can preserve brain energy metabolism during HCA at 20°C in a rat model.
• To compare the efficacy of different perfusates in maintaining brain energy levels and preventing edema.

Main Methods:

• Wistar rats underwent surface cooling to 20°C followed by 20 minutes of HCA.
• Three perfusates were tested during RCP: hemoglobin-free saline, rat red blood cells, and liposome-encapsulated hemoglobin, all made hypertonic and oxygenated under pH-stat management.
• Brain tissue was analyzed for high-energy phosphates, adenosine, and water content.

Main Results:

• Liposome-encapsulated hemoglobin and rat red blood cell perfusates significantly preserved brain adenosine triphosphate (ATP) levels and energy charge compared to saline or HCA alone.
• Both optimized perfusates maintained significantly higher energy levels (P = 0.0419-0.0001).
• RCP with hypertonic solutions effectively prevented brain edema.

Conclusions:

• Optimized perfusate composition, particularly with rat red blood cells or liposome-encapsulated hemoglobin, significantly reduces ischemic energy depletion during HCA.
• These findings suggest that optimized RCP can provide beneficial aerobic metabolic support to the brain during HCA.