Purpose To evaluate and quantify microvascular perfusion changes with contrast enhanced ultrasound (CEUS) in the brain during and after hypoxic injury. Can CEUS be used in early detection of brain injury after hypoxia?

Material and Methods Anaesthetized newborn piglets (n = 11) were exposed to 30 min hypoxia followed by resuscitation with 21% or 100% O₂ and reoxygenation for seven hours. Transcranial CEUS was performed in midline coronal plane prior to, during and repeatedly up to seven hours after the hypoxia. CEUS perfusion analyses were performed by tracing regions of interest (ROI); in the ICA, basal ganglia (BG) and parasagittal cortex and one large ROI of the whole brain. Time intensity curves were analyzed for time to peak (TTP), peak intensity (PI) and the rate parameter (β). Ratios of between the BG/ICA, cortex/ICA, cortex/BG and whole brain/ICA for these parameters were calculated and compared for different time points. p<0.05 was considered statistically significant.

Results CEUS performed during hypoxia showed perfusion changes with increased ratios for TTP, slightly increased for PI and reduced for β compared to baseline values. During the resuscitation/early reoxygenation there was a short phase of hyperperfusion with development towards reduced perfusion at the endpoint with increasing ratios for TTP and decreasing for PI and β. There was 40% increase in TTP during hypoxia for the whole brain/ICA (p<0.05). Correlation to histological findings and more detailed and extensive results will be reported.

Conclusion Quantification of cerebral perfusion changes in the piglet brain is feasible with transcranial CEUS. During and after hypoxia, CEUS revealed perfusion changes with marked decreased perfusion seven hours after hypoxia.