Cardiac 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]fluorodeoxyglucose (FDG)-Positron emission tomography (PET) to study in vivo cerebral glucose metabolism 72 h following CA in a murine CA model.
Anesthetized and ventilated adult C57BL/6 mice underwent 12-min KCl-induced CA followed by CPR. Seventy-two hours following CA, surviving mice were intraperitoneally injected with [18F]FDG (~ 186 µCi/200 µL) and imaged on Molecubes preclinical micro-PET/computed tomography (CT) imaging systems after a 30-min 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 Positron emission tomography (PET) imaging, remaining [18F]FDG radioactivity in the brain, heart, and liver was determined using a gamma counter.
Global increases in brain [18F]FDG uptake in post-CA mice were observed compared to shams and controls. The median standardized uptake value of [18F]FDG for CA animals was 1.79 versus sham 1.25 (p < 0.05) and control animals 0.78 (p < 0.01). This increased uptake was consistent throughout the 60-min 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 was 7.04%ID/g tissue for CA mice versus 5.537%ID/g tissue for sham animals, p < 0.05).
This 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 h following CA, suggesting increased metabolic demand in the case of severe neurological injury. Further study is warranted to determine the etiology of these changes.