Diagnosis of perinatal hypoxic-ischemic encephalopathy using near-infrared spectroscopy to measure cerebral metabolism

Birth is associated with a risk for asphyxia-induced hypoxic-ischemic brain damage, principally due to complications during delivery. An important hallmark of hypoxic-ischemic encephalopathy is that it often requires hours to days to manifest after resuscitation: the result is that early prognosis and treatment could potentially improve outcomes. Unfortunately, conventional methods for predicting outcome suffer from poor specificity. Consequently, neonatal intensive care would benefit greatly from the development of a safe and portable method for the early prognosis of brain injury at the bedside. The purpose of this thesis was to validate and assess the diagnostic capabilities of a novel near-infrared spectroscopy (NIRS) technique designed to measure cerebral metabolic rate of oxygen (CMRO2) in-vivo.;The validation of the NIRS technique is described in Chapter 2. Measurements of CMRO2 were calculated from NIRS and from a gold standard blood-sampling technique, simultaneously, over a range of cerebral metabolic states in piglets. Five different metabolic states were created by changing the dose and type of anesthetic agent. It was found that the NIRS CMRO2 measurement had a strong correlation with the gold standard technique, with a 95%-confidence interval of 13%.;Chapter 3 describes the response of cerebral hemodynamics and metabolism to hypoxia-ischemia as assessed by the measure of cerebral blood flow and CMRO2, calculated using NIRS. No significant response of blood flow to injury was observed, while CMRO2 presented an immediate and persistent 25%-reduction. The retained accuracy of the LAIRS CMRO 2 measurement following hypoxia-ischemia is also demonstrated.;Chapter 4 summarizes an investigation of the prognostic value of the LAIRS CMRO2 measurements following hypoxia-ischemia. A significant correlation was found between insult duration and CMRO2 after 8 hours of reperfusion: prior to 8 hours, a similar depression of CMRO 2 was observed for all injuries regardless of severity.;The results of this thesis establish the LAIRS technique---which has been designed as the first apparatus capable of rapidly and safely measuring CMRO2 at the bedside---as a promising tool for prognosis and treatment planning of hypoxic-ischemic encephalopathy in the critically ill newborn.;Keywords: Near-infrared Spectroscopy, cerebral metabolic rate of oxygen, cerebral blood flow, hypoxic-ischemic encephalopathy, neonate, piglets...