Noninvasive detection of changes in cerebral blood flow by near-infrared spectroscopy in a piglet model of hydrocephalus

Formulation of rational interventions in infantile hydrocephalus is limited by the inability to monitor cerebral hemodynamics quantitatively, continuo usly, and noninvasively. Near-infrared spectroscopy (NIRS) measures changes in cerebral concentration of oxygenated and deoxygenated hemoglobin (HbO(2 ) and Hb); HbD is the derived difference between HbO(2) and Hb. Our previou s work showed that HbD reflected cerebral blood flow (CBF) measured by radi oactive microspheres in a piglet model of systemic hypotension. This study was designed to determine whether NIRS detected important changes in cerebr al perfusion and oxygenation in a piglet model of hydrocephalus and whether changes in HbD accurately reflected changes in CBF. Acute hydrocephalus wa s produced in neonatal piglets by intraventricular infusion of "mock cerebr ospinal fluid." Intracranial pressure (ICP) was maintained for several minu tes at approximately 10, 20, and 30 mm Hg above the baseline ICP. CBF was m easured in cerebral cortex, white matter, and basal ganglia at each ICP by radioactive microspheres. Changes in HbO(2) and Hb were measured continuous ly by NIRS. Cerebral perfusion pressure declined with increasing ICP, and t his decline was accompanied by significant decreases in HbD measured by NIR S and CBF measured by radioactive microspheres. There was a strong correlat ion between changes in HbD and individual changes in CBF in cerebral cortex , white matter, and basal ganglia tall p < 0.0001). This study demonstrates that changes in HbD reflect changes in CBF over a wide range of ICP in a m odel of acute hydrocephalus. This reproducible and easily obtained measurem ent by NIRS could facilitate considerably decisions concerning therapeutic interventions.