New non-invasive methods for the investigation of cerebral oxidative metabolism and haemodynamics in newborn infants.

Magnetic resonance spectroscopy and near infrared spectroscopy provide complimentary information about cerebral oxidative metabolism and haemodynamics and are valuable methods for investigating normal brain development and the pathogenesis of perinatal brain injury. Magnetic resonance spectroscopy can be used to measure in brain tissue the concentrations of important phosphorus compounds that are involved in oxidative metabolism, notably adenosine triphosphate, phosphocreatine and inorganic orthophosphate: intracellular pH can also be estimated. Abnormalities indicating impaired oxidative phosphorylation have been detected in a range of situations where hypoxic-ischaemic brain injury was known or suspected to have occurred, such as birth asphyxia and periventricular leucomalacia. Following acute cerebral injury a latent period of many hours has frequently been found before evidence of impaired oxidative phosphorylation developed, suggesting the possibility of effective early treatment. The extent of the metabolic impairment was related to long term outcome. Near infrared spectroscopy provides cotside information about cerebral oxygenation and haemodynamics. Quantitative information can be obtained about oxyhaemoglobin, deoxyhaemoglobin and the redox state of cytochrome aa3. Methods have been described for calculating cerebral blood flow, oxygen delivery, blood volume and carbon dioxide reactivity; and maturational changes are being defined. In birth-asphyxiated babies, abnormalities are detectable well before oxidative phosphorylation becomes impaired.