Assessment of Brain Glucose Metabolism Following Cardiac Arrest by FDG Positron Emission Tomography

BackgroundCardiac arrest (CA) patients who survived by cardiopulmonary resuscitation (CPR) can present different levels of neurological deficits ranging from minor cognitive impairments to persistent vegetative state and brain death. The pathophysiology of the resulting brain injury is poorly understood and whether changes in post-CA brain metabolism contribute to the injury are unknown. Here we utilized [18F]FDG-PET to study in vivo cerebral glucose metabolism 72 hours following CA in a murine cardiac arrest model. MethodsAnesthetized and ventilated adult C57BL/6 mice underwent 12-minute KCl-induced CA followed by CPR. Seventy-two hours following cardiac arrest, surviving mice were intraperitoneally injected with [18F]FDG (~186 Ci/200 L) and imaged on Molecubes preclinical micro PET/CT imaging systems after a 30-minute awake uptake period. Brain [18F]FDG uptake was determined by the VivoQuant software on fused PET/CT images with the 3D brain atlas. Upon completion of PET imaging, remaining [18F]FDG radioactivity in the brain, heart, and liver was determined using a gamma counter. ResultsGlobal increases in brain [18F]FDG uptake in post-CA mice were observed compared to shams and controls. The median standardized uptake value (SUV) of [18F]FDG for CA animals was 1.79 vs. sham 1.25 (p<0.05) and control animals 0.78 (p<0.01). This increased uptake was consistent throughout the 60-minute imaging period and across all brain regions reaching statistical significance in the midbrain, pons, and medulla. Biodistribution analyses of various key organs yielded similar observations that the median [18F]FDG uptake for brain were 7.04%ID/g tissue for CA mice vs 5.537%ID/g tissue for sham animals, p<0.05). ConclusionsThis study has successfully applied [18F]FDG-PET/CT to measure changes in brain metabolism in a murine model of asystolic CA. Our results demonstrate increased [18F]FDG uptake in the brain 72 hours following CA, suggesting increased metabolic demand in the case of severe neurological injury. Further study is warranted to determine the etiology of these changes.