Extracorporeal membrane oxygenation (ECMO) is an important therapy for critically ill children but survivors have neurodevelopmental impairments. Cerebral inflammatory response resulting in brain edema is observed on ECMO. This pathologic response may adversely impact the quantitative accuracy of diffuse optical spectroscopy (DOS) neuromonitoring (including commercial NIRS) which commonly assumes a 75% water fraction. Using fresh brain tissue desiccation, we directly quantified the severity of cerebral edema in pediatric swine following cardiac arrest, CPR and 22-24 hours of ECMO therapy. The fractional error in DOS quantification of cerebral hemodynamics from assuming 75% water fraction was determined to be <5%.
Hydrocephalus is a disorder of cerebral spinal fluid (CSF) physiology that results in increased intracranial pressure (ICP). It is commonly treated via surgical placement of a shunt in the ventricles to divert CSF. Diffuse optical measurements of cerebral perfusion and oxygen extraction were acquired before and after surgical shunt placement in neonates with hydrocephalus. An invasive ICP measurement was made at the time of shunt placement. Shunting increased cerebral perfusion and decreased oxygen extraction only in infants with elevated ICP. This suggests abnormally low perfusion in patients with elevated ICP, and normal perfusion in patients without elevated ICP.
We examine the correlation of non-invasive, frequency-domain diffuse optical spectroscopy (FD-DOS) and diffuse correlation spectroscopy (DCS) measurements of cerebral tissue oxygen extraction fraction (OEF) and relative cerebral blood flow (rCBF) with invasive cerebral microdialysis measurement of the cerebral lactate-pyruvate ratio (LPR), a biomarker of metabolic stress, during extracorporeal membrane oxygenation (ECMO) in a pediatric swine model of ECMO assisted cardiopulmonary resuscitation (n=15). During 22-24 hours of ECMO, non-invasive FD-DOS/DCS neuromonitoring of OEF and rCBF demonstrated significant correlations with cerebral LPR. Non-invasive detection of critical neurometabolic stress at the bedside may facilitate brain-targeted ECMO management after cardiac arrest.
Mild hypothermic cardiopulmonary bypass (CPB) is used during neonatal cardiac surgery. To elucidate potential risk factors for brain injury, diffuse optical spectroscopy, diffuse correlation spectroscopy, and cerebral microdialysis techniques were employed to monitor cerebral hemodynamics during mild hypothermic CPB in a swine model. Optical metrics were further compared with microdialysis metrics. Stable microdialysis metabolite levels, a significant decrease in CMRO2, and trending (but not significant) decreases in CBF and increases in OEF were observed. This suggests that the optical metrics may be more sensitive to neurologic injury during CPB than microdialysis.
Evaluation of the brain’s resting-state is an important window into neuronal function, connectivity, and health. Resting-state brain activity is reflected via neurovascular coupling in low frequency (0.01-0.1 Hz) hemodynamics, and low frequency power (LFP) can be a proxy for regional neuronal activity. In this exploratory study, we measured LFP in cerebral blood flow using diffuse correlation spectroscopy (LFP-DCS) during the course of an asphyxial cardiac arrest model in pediatric swine. The data demonstrate that LFP-DCS has distinct temporal information to blood flow index and may provide an additional biomarker to predict successful recovery after neurologic insults.
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