Hypoxic Ischaemic Encephalopathy Flashcards
What is HIE?
An acquired syndrome of acute brain injury characterized by neonatal encephalopathy and evidence of intrapartum hypoxia
What is the prognosis for infants with moderate or severe HIE?
25-90% chance of developmental delay and/or CP, depending on severity and treatment
What is neonatal encephalopathy?
Abnormal level of consciousness and abnormal tone and reflexes, often with abnormal breathing, abnormal feeding and seizures
What are the causes of neonatal encephalopathy? (6)
- Sepsis
- Brain malformation/damage
- Metabolic abnormality (e.g. Hypoglycaemia)
- Drug withdrawal (neonatal abstinence)
- Abnormal brain perfusion (shock, cardiac failure, trauma)
- Intrapartum hypoxia and ischaemia
What is birth asphyxia?
Failure to initiate and sustain spontaneous breathing after birth. Shown by low apgars
What causes birth asphyxia? (5)
Sedation via maternal medication/drug abuse Fetal infection Fetal congenital anomaly Trauma/ haemorrhage Intrapartum hypoxia and ischaemia
What is intrapartum hypoxia?
Impaired gas exchange leading to progressive fetal hypoxaemia and hypercapnea with a significant metabolic acidosis
What is the normal base deficit at birth
Base excess -0.3 to -6.3 (base deficit of 0.3- 6.3)
What 2 parameters on cord gas/early blood gas show hypoxia/asphyxia severe enough to cause CP?
BE and pH. Indicate metabolic acidosis. BE >12mmol/l and art cord pH
What signs are suggestive of intrapartum hypoxia or fetal asphyxia severe enough to cause CP?
Sentinel hypoxic event Sudden deterioration of FHR pattern Multisystem involvement Imaging evidence Apgars of 0-6 for >5 min
At what point is base deficit abnormal? What does this suggest?
Base deficit of >10mmol/l is abnormal and suggests intrapartum hypoxia
How does the fetus respond to hypoxia and ischaemia in utero?
Response: fetal bradycardia ms diving reflex (blood is diverted to the brain)
What occurs in prolonged hypoxia?
Cardiac failure
Anaerobic metabolism –> accumulation of lactic acid –> metabolic acidosis
What brain regions are affected by hypoxia? What is the pattern of injury!
Basal ganglia and subcortical white matter
Injury follows in phases
What ratio represents failed oxidative metabolism?
A decreasing PCr/Pi ratio
What does a decreasing PCr/Pi ratio represent?
Failure of oxidative metabolism
What are the 6 parameters used to stage HIE?
Level of consciousness Activity Neuromuscular control Primitive reflexes Autonomic function Seizures
How many stages of HIE are there?
3
What are the 9 parameters used in the Thompson HIE score?
Limb tone Level of consciousness Visible fits Posture Moro Grasp Suck Respiratory effort Fontanel
What are the Grade 3 signs according to the Thompson score?
Flaccid (limb tone)
Comatose or stuporose (level of consciousness)
Decerebrate (posture)
Apnoeic (respiratory effort)
What are the 6 types of subtle neonatal seizures?
Ocular (tonic deviation+/- jerking, staring, fixed blinking)
Oral-Buccal-Lingual (chewing, facial wincing, cry-grimace)
Limb movements (boxing, cycling, stepping)
Autonomic (Brady/tachycardia, tachypnoea)
Apnea
What are the 3 classes of neonatal seizures?
Subtle
Tonic
Clonic
What causes neonatal seizures?
Hypoglycaemia Hypoxia HIE Brain damage, haemorrhage, trauma Meningitis Electrolyte/ metabolic abnormalities Drug withdrawal Abnormal brain perfusion
How is CNS function assessed and monitored in infants with HIE?
Amplitude integrated EEG (aEEG)
Cerebral ultrasound
MRI
What is the most useful prognostic tool and what is a good prognostic sign?
aEEG
Normal aEEG at age 6 hours correlates with normal outcome
What is cerebral ultrasound used for and what can it show?
It is used to exclude congenital cerebral anomalies
It can show oedema, infarction, haemorrhage acutely and later cystic changes
What can be seen on MRI and how is this helpful?
It shows cerebral injury
Can help prognosticate
What is therapeutic hypothermia?
Whole body cooling to 33-34, or selective head cooling to 34-35.
How is therapeutic hypothermia administered?
Consistent with clearly defined protocols
In NICU (IPPV, sats, BP monitors, inotropes available)
Started within 6 hours of birth for 72 hours
Rewarmed slowly over at least 4 hours
Monitor for adverse effects
Follow up
What are the mechanisms of therapeutic hypothermia?
Metabolic depression allowing energy conservation. Specific inhibition of apoptosis
Improved protein synthesis
Inhibition of glutamate release
Decreased intracellular acidosis and free radical generation
Reduced NO production and BBB breakdown
Decreases inflammatory response
What are the cooling criteria in HIE?
A. All of the following: >=35/52 and >=1.8 kg; 10; or 5min Apgar
What is the Shankaran definition of moderate encephalopathy?
One or more of the following: Lethargic (level of consciousness), decreased spontaneous activity, distal flexion with complete extension (posture), hypotonia (focal/general), weak suck/ incomplete Moro, constricted pupils/ bradycardia/ periodic breathing.
What is the Shankaran definition of severe encephalopathy?
One or more of the following: Stupor/coma, no spontaneous activity, decerebrate posture, flaccid (tone), absent suck/Moro, deviated/dilated/nonreactive pupils/ variable heart rate/ apnoeic.
What else can go wrong in HIE?
Lungs- surfactant depletion and delayed lung fluid clearance; pulmonary hypertension
CVS- cardiac dysfunction
Renal- failure, hyponatraemia, hypokalaemia
SIADH (hyponatraemia)
Hepatic- hypoglycaemia, low albumin, coagulopathy, jaundice
GIT- ileus/’NEC
Bone marrow- thrombocytopenia
What is the fluid management in an HIE baby with renal failure?
Fluids restricted to 40ml/Ig maintenance Avoid boluses unless hypovolaemic Use K-free fluids Monitor glucose (12.5-15% dextrose if low)
What are the paO2 and paCO2 goals in an HIE baby?
O2- 8-10.6 kPa, 60-80mmHg
CO2- 4.4-6 kPa, 33-52.5 mmHg
What is the primary care (systems approach) of HIE babies?
Brain- treat seizures: airways, breathing, glucose, phenobarbital
Lungs- monitor O2 sats, treat resp failure
CVS- monitor pulse and perfusion
Renal- monitor urine outputs, avoid too much fluid
Hepatic- monitor blood glucose
GIT- avoid feeds unless signs are mild, IV fluids preferable
Bone marrow/immunity- monitor colour and signs of bleeding
What is the management of infants with low Apgar scores?
If ongoing ventilation or signs of mod/severe HIE- admit to ICU/HC, aEEG, cool
CPR or BD>10 but good response to resus, no signs mod/severe HIE-bad it to observation area, feed cautiously, routine obs, early glucose check, watch for HIE signs or seizures
Some resus (no CPR) but normal by 10mins normal blood gas and normal glucose- stay with mum
What are the signs of stage 1 HIE?
Irritability, increased tone, poor sucking, exaggerated Moro with jitteriness and fisting
What are signs of stage 2 HIE?
Lethargy, decreased tone and primitive reflexes, often with seizures
What are signs of stage 3 HIE?
Stupor or coma, flaccid, apnoeic
What is the aim of management of HIE babies?
To treat the signs and reduce further organ damage
How is an HIE a baby managed?
Prevent fetal hypoxia. Prompt resus. Document and record neurological signs daily. Routine monitoring of vital signs and manage complications. Record HC at birth and daily. Document cerebral sonography during adm and at dc. Treat convulsions. Restrict fluid intake. Supplementary O2 and resp support if needed. Counsel parents.
An abnormal Thompson score on day 7 indicates what?.
Poor neurological development
What does a Thompson score of >15 indicate?
Increased mortality
When is follow up performed?
At 20 corrected weeks
What brain damage is commonly seen in survivors of severe HIE?
Microcephaly, CP and mental retardation
What sign is seen on cranial sonography indicating persistent damage and in what regions is it prevalent?
Leucomalacia- densities or cystic change
Seen in the subcortex, cortex or basal ganglia
