Neonates With Hypoxic Ischemic Encephalopathy (HIE)

Encephalopathy in neonates is broadly defined as brain dysfunction in a newborn manifesting as alteration in mental status and abnormal neurologic examination. Neonatal encephalopathy (NE) may result from acute or chronic hypoxic-ischemic injury, brain malformations, vascular injuries (including stroke), inborn errors of metabolism, and other causes. Hypoxic-ischemic encephalopathy (HIE) is a specific diagnosis and applies only when a neonate has encephalopathy that is known or highly suspected to be due to a hypoxic-ischemic event.

Perinatal asphyxia is a condition where hypoxaemia and acidosis are present in the fetus or the newborn infants. It is a failure newborn to initiate spontaneous, sustained, and vigorous respiration effort at birth. It is also defined as a failure to initiate spontaneous respirations and/or a 5-minute Apgar score of less than 7: the most commonly used indicator in the identification of birth asphyxia in resource limited settings . About 20% - 30% of asphyxiated newborns who develop hypoxic ischemic encephalopathy (HIE) die during the neonatal period, and one third to one half of survivors are left with cerebral palsy and mental retardation . Survivors present with several short and long term morbidities, including: seizure disorders, tone abnormalities, feeding difficulties, delayed developmental milestones, learning difficulties, cerebral palsy and mental retardation. The frequency of severe perinatal asphyxia complications, hypoxic ischemic encephalopathy (HIE) and incidence of up to 26.5/1000 live births is unacceptably high despite advances in perinatal care . Encephalopathy occurs in 50% to 60% of patients with severe perinatal asphyxia. Among patients with moderate HIE, 10% to 20% die, and 30% to 40% develop neurodevelopmental disorders, whereas 50% of patients with severe HIE die and almost all survivors develop neurodevelopmental deficits Neuro-science research has revealed our understanding of the mechanisms by perinatal asphyxia neuronal damage and adverse consequences. Asphyxia leads to two types of cerebral injuries: the primary neuronal injury that occurs at the time of hypoxic-ischemic insults and the secondary cerebral injury that occurs over hours to days after accumulation of excessive intra-neuronal calcium through stimulation of the excitatory N-methyl-D-aspartate (NMDA) glutamate receptors, which triggers apoptosis of the affected neurons . Magnesium is a naturally occurring NMDA receptor antagonist that blocks neuronal influx of calcium within the ion channels. This block is voltage-dependent and is overcome during axonal depolarization that occurs in hypoxic-ischemic insults. If the extra-cellular magnesium concentration is increased, this blockade can be restored. Magnesium sulphate may also have direct actions on mitochondrial activity, anticonvulsant properties and hemodynamic effects by increasing cerebral blood flow. Some data also suggest that MgSO4 may serve an anti-apoptotic role and prevent neuronal cell loss .

Clinical studies have shown that caffeine also has neuroprotective effects in premature infants by alleviating hypoxia induced white matter damage, and improving ventilation function and brain self-regulation In addition, caffeine has been shown to reduce the apoptosis of developing brain neurons, ventricular enlargement, and white matter loss caused by hypoxia.