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