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Hypoxic Ischemic Encephalopathty E h l hOsama Naga, M.D. PGY2 7/21/09
HIE
BackgroundClinical and laboratory evidence of acute or subacute brain injury due to asphyxia Asphyxia means absence of pulse literally Underlying cause remains unknown The exact time of brain injury often remains uncertain
HIE
Pathophysiology
The primary physiological processes that lead to hypoxichypoxic-ischemic encephalopathySystemic hypoxemia Reduced cerebral blood flow (CBF) ( ) Both
HIE
Pathophysiology Early compensatory adjustments
Hypoxia and hypercapnia
Increase in the CBF
Increase cardiac output BP increase
Early compensatory adjustments fail
BP falls
CBF falls below critical levels
Brain suffers from diminished blood supply Lack of sufficient oxygen to meet its needs. needs
Pathophysiology
HIE
Pathophysiology
During the early phases of brain injury, brain temperature drops
Local release of neurotransmitters, such as (GABA) increase
Reduce cerebral oxygen demand, transiently minimizing the impact of asphyxia
HIE
Pathophysiology
The magnitude of the final neuronal damage dependsInitial insult Damage due to energy failure g gy Reperfusion injury Apoptosis
HIE
HIE
Incidence
2-4 cases per 1000 births
Mortality t M t lit rateSevere HIE the mortality rate has been reported to be 50b 50-75% Most deaths (55%) occur in the first week of life due to multiple organ failure
HIE
History
AAP CriteriaProfound metabolic acidosis Mixed acidemia (pH
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