Hybrid diffuse optical monitoring of hemodynamic changes following acute cerebral ischemia in a porcine model

Rapid screening for stroke in pre-hospital settings may improve patient outcomes by allowing early deployment of thrombolytic therapies. Near-infrared hybrid diffuse optical screening devices may fill this need. This study seeks to determine whether hybrid diffuse optical measurements can measure hemodynamic changes associated with cerebral ischemia within the first few hours of the onset of acute ischemia in a large animal model. A hybrid diffuse optical device combining of near-infrared spectroscopy (NIRS) and diffuse correlation spectroscopy (DCS) was fabricated to measure total hemoglobin concentration (HbT), tissue oxygen saturation (StO2) and blood flow index (BFI). Cerebral ischemia was induced by ligation of the bilateral common carotid arteries (CCA) in five miniature pigs. Additionally, a fatal stroke was induced in two pigs by injecting 5ml air emboli into both CCA. Cerebral hemodynamic parameters were monitored continuously throughout the study with the hybrid optical device. Relative changes BFI showed the good repeatability both of the ligation and fatal stroke experiments. During bilateral CCA ligation, the BFI decreased by up to about 66% of baseline values; during the fatal stroke experiment, the BFI decreased by up to about 95%, with a temporal resolution of 20 seconds. To the best of our knowledge, there are not existing methods which can measure the cerebral ischemia within the first few hours of the onset noninvasively. The MRI scanning was conducted at 24 h post injury. However, the images showed no abnormality. The results show the hybrid diffuse optical method can immediately measure the hemodynamic changes of miniature pigs in the first few hours of each single cerebral ischemia onset, and the BFI may be the promising biomarker to distinguish the cerebral ischemia and cerebral death.