The Clinical Spectrum and Prediction of Outcome in Hypoxic-Ischemic Encephalopathy

Abstract

After completing this article, readers should be able to: 1. List the signs related to problems in labor and immediately following birth used to diagnose hypoxic-ischemic encephalopathy (HIE). 2. Compare and contrast the grade of HIE and Apgar score for predicting outcome. 3. Describe the role of likelihood ratios in altering diagnostic and prognostic probabilities. 4. Compare and contrast the electroencephalogram and newer technologies in assessing outcome early in the course of HIE. The major problem that confronts those caring for infants who have hypoxic-ischemic encephalopathy (HIE) is how to provide families with reliable information about outcome. These infants present few diagnostic problems, and treatments are mostly supportive. The difficulty lies in how long to pursue treatment in infants who may have a very poor prognosis. This review presents a scheme for predicting outcome based on information gathered over the past three decades using a combination of clinical assessment and routine neonatal electroencephalography (EEG). This approach is contrasted with more recent methods of assessing prognosis using evoked potentials, near-infrared spectroscopy, and imaging (see NeoReviews, January 2001), including manipulations of magnetic resonance imaging. After determining whether the newer technologies simply complement or actually improve outcome prediction based on the simpler investigations, the use of higher-tech, and less available, tests can be assessed for specific clinical situations. Birth asphyxia, defined as an Apgar score of less than 7 at 5 minutes, with exclusion of congenital infection, malformation, or opioid-induced respiratory depression, occurred in 5.4 per 1,000 liveborn infants born between 1985 and 1991 in Goteborg, Sweden. Of these “asphyxiated” infants, HIE occurred in one third for an incidence of 1.8 per 1,000. HIE occurred at a rate of 6 per 1,000 in a 4-year English study published in 1985. Thus, the compromised infant who has a significant encephalopathy is seen regularly in active obstetric services. There …