Defining Features and Aetiology of Hypoxic‐Ischaemic Encephalopathy

This thesis seeks to set out the background, methods, results and discussion and conclusion of an observational study of the defining features and aetiology of moderate-severe hypoxic-ischaemic encephalopathy (HIE). Firstly, the epidemiology, pathophysiology and treatment of HIE are outlined. A number of existing epidemiological definitions are described, compared and contrasted. The difficulties of defining HIE clearly and consistently for epidemiological purposes are discussed. The role of intrapartum hypoxia and other aetiological factors in HIE is introduced. The challenges of exploring the aetiology of HIE are discussed. The consideration of potential methodologies to study this topic is described. The aims and objectives of the study are presented. The design of the study and study components are each then described in turn. These include the pilot study, retrospective cohort study, development of a reference standard by expert consensus, observational study of possible aetiological factors, and measurement of validity of epidemiological definitions are each described in turn. The results of the study are described in turn. 168 infants with symptoms of neonatal encephalopathy were identified and notes were obtained for 153 of these infants. The observed maternal, neonatal and paediatric features of these infants and the development of a reference standard by expert consensus are described. The application of the reference standard to the study population leading to the identification of 54 infants with neonatal encephalopathy (NE) of whom 29 (53.7%) infants had moderate-severe HIE, is described. The prevalence of possible aetiological factors in infants with NE and the HIE and non-HIE subgroups are described. Finally, the study findings, strengths and limitations are discussed. The defining features of HIE and the prevalence of risk factors in this population compared to similar studies where available, are presented. The implications of these findings for future clinical practice and research are discussed.