Hypoxic Ischemic Encephalopathy Flashcards
What is hypoxic-ischaemic encephalopathy (HIE)?
Hypoxic-ischaemic encephalopathy (HIE) is neonatal encephalopathy (NE) that occurs in the first two days of life and is caused by intrapartum hypoxia and cerebral ischemia.
How is neonatal encephalopathy (NE) characterized?
Neonatal encephalopathy is characterized by an abnormal level of consciousness, abnormal tone, and abnormal primitive reflexes.
What are some common manifestations of neonatal encephalopathy (NE)?
Seizures and feeding difficulties commonly occur in moderately or severely affected infants with neonatal encephalopathy.
Besides intrapartum hypoxia, what are some other causes of neonatal encephalopathy (NE)?
Other causes of neonatal encephalopathy include
-hypoglycemia,
-electrolyte disturbances,
-sepsis,
-drug effects,
-haemodynamic disturbances,
-brain malformations,
-inborn errors of metabolism, and
-neonatal epileptic syndromes.
How common are the causes of neonatal encephalopathy (NE) compared to intrapartum hypoxia?
While intrapartum hypoxia is the most common cause of neonatal encephalopathy, the other mentioned causes are less common but must be considered during the assessment of NE.
What physiological changes occur during intrapartum fetal hypoxia?
Initially, there is fetal bradycardia, and blood flow is shunted towards the brain. However, this shunting compromises the perfusion of other organs.
What happens if hypoxia continues during intrapartum fetal hypoxia?
If hypoxia continues, the myocardium becomes critically hypoxic, leading to a decrease in cardiac output and subsequent cerebral ischemia.
Which areas of the brain are most affected by cerebral ischemia during intrapartum fetal hypoxia?
In term infants, the basal ganglia (due to their high metabolic rate) and subcortical white matter (due to being in the “water-shed” zone) are most affected by cerebral ischemia.
What are the expected neurological outcomes in cases of moderate and severe intrapartum fetal hypoxia?
In some cases of moderate and most cases of severe intrapartum fetal hypoxia, spastic quadriplegic or dyskinetic cerebral palsy is the expected neurological outcome.
Why is it important to diagnose hypoxic-ischaemic encephalopathy (HIE) promptly?
It is crucial to diagnose HIE promptly so that appropriate supportive care can be provided and interventions such as therapeutic hypothermia can be considered for moderately or severely affected infants.
What is the time frame for initiating therapeutic hypothermia in infants with HIE?
Therapeutic hypothermia must be started within 6 hours of life in infants with hypoxic-ischaemic encephalopathy (HIE).
The following findings suggest that the intrapartum hypoxia and ischaemia were of
sufficient severity to potentially cause brain damage:
- Metabolic acidosis with base deficit ≥ 10mmol/l in umbilical arterial blood or the
infant’s arterial blood within the first hour of life or the ongoing need for assisted
ventilation 10 minutes after birth. - Intrapartum signs or events suggesting fetal compromise or Arterial Cord pH < 7.0.
- Severe or moderate encephalopathy during the first 48 hours of life.
How do the clinical signs in infants with hypoxic-ischaemic encephalopathy (HIE) typically evolve over time?
The clinical signs in infants with moderate or severe HIE typically become increasingly obvious or severe during the first 48 to 72 hours of life.
What are common manifestations of seizures in infants with HIE?
eizures in infants with HIE are often clinically silent, but they may also present as rhythmic clonic movements. More frequently, seizures manifest as subtle signs including buccal-lingual movements, abnormal eye movements, cycling movements of limbs, abnormal tonic posturing, or grimacing.
How can cycling, posturing, and myoclonus in infants with HIE be differentiated from seizures?
Cycling, posturing, and myoclonus may alternatively represent a lack of inhibition/control at a brainstem level. EEG confirmation is required to distinguish the etiology of these movements from seizures.
Stage 1 of encephalopathy
Irritability, increased tone, poor sucking but an exaggerated moro reflex.
Stage 2 of encephalopathy
Lethargy, decreased tone and primitive reflexes. Seizures are common.
Stage 3 of encephalopathy
Stupor or Coma, flaccid tone and seizures often clinically less apparent.
Why is EEG confirmation necessary in infants with hypoxic-ischaemic encephalopathy (HIE)?
EEG confirmation is required to distinguish the etiology of certain clinical signs, such as cycling, posturing, and myoclonus, from seizures in infants with HIE.
What does progression through the stages of hypoxic-ischaemic encephalopathy (HIE) represent?
Progression through the stages of HIE represents continuing damage occurring after birth due to reperfusion injury and oxidant damage caused by an excitotoxic cascade at a cellular level.
Why might some infants not manifest a typical progression through the stages of HIE?
Some infants are born with established damage and may not exhibit a typical progression through the stages of HIE.
How might the severity and prognosis of HIE be more reliably assessed?
The severity and prognosis of HIE may be more reliably assessed using a detailed HIE score known as the Thompson HIE Score, as there is much overlap between the signs within the stages.
What is aEEG and what is its significance in cerebral function monitoring?
aEEG is a time-compressed, processed EEG used for diagnosing subclinical seizures and providing prognostic value in cerebral function monitoring.
How does aEEG compare to clinical examination in assessing cerebral function?
aEEG is more objective than clinical examination, making it valuable for diagnosing subclinical seizures.
When should aEEG be applied in cerebral function monitoring?
aEEG should be applied as soon as possible where available for optimal diagnosis and prognosis.
What can cranial ultrasound reveal in cerebral function monitoring?
Cranial ultrasound may show established damage at birth such as oedema, infarction, ischemia, or hemorrhage, as well as evolving focal or global injury.
What is the primary aim of assessing and managing infants with HIE?
The primary aim is to minimize further organ damage.
What key aspects should be documented in the assessment of infants with HIE?
Document antenatal history, intrapartum events, and management at delivery.
Why is medicolegal investigation becoming more common in cases of HIE?
Medicolegal investigation is increasing due to the need for accountability and understanding the circumstances surrounding HIE cases.
How does documenting intrapartum events help in managing infants with HIE?
Documenting intrapartum events assists in understanding potential causes and guiding appropriate management strategies for infants with HIE.
What precautions should be taken during resuscitation at birth for infants with HIE?
Avoid over-heating and hyperoxia during resuscitation.