Asphyxia/HIE Flashcards
T/F: there are many reasons for encephalopathy
True
In HIE, encephalopathy is caused by either a lack of _______ or oxygen delivery to the brain.
Perfusion
Encephalopathy is a clinical syndrome w/abnormal _____ function as manifested by: (4 things)
CNS function: Abnormal LOC Seizures Tone Reflexes
HIE is abnormal neurologic behavior following _____ _____ or ischemia.
perinatal hypoxia
What are the 2 ways the brain is deprived of oxygen?
Hypoxia: diminished O2 to the brain
Ischemia: diminished amount of blood perfusing the brain
What 3 types of insults should alert you to possible HIE and which group is the most susceptible?
- Maternal
- Utero-Placental (most susceptible)
- Fetal
During what periods do most HIE events occur? What is the %.
Antepartum and Intrapartum periods just before or during delivery
Accounts for 35% of HIE
HIE incidence in the developed world =
1-2 per 1000 live term births
Is HIE higher/lower in the developing world?
Higher
HIE is the most _______ cause of neurologic dz in the neonatal period.
common
HIE can result in what disorders?
6 things
- Hearing loss
- Learning disability
- Mild motor dysfunction
- CP
- Severe motor dysfunction
- Death
The hypoxic event is followed by what?
Reperfusion injury
What are the 2 phases of injury/damage to the brain?
What phase is in between?
Early/primary: cerebral hypoxia (no oxygen/no blood to brain)
Late/Secondary: Reperfusion injury
Latency phase: our opportunity betwen 6-15 hours to intervene to try to avoid Secondary/reperfusion injury
Which phase is characterized by failure to create ATP as a result of decreased blood flow to the brain?
Primary/early phase
During the early phase, cells are _______ –>lots of necrosis of brain tissue itself.
exploding
When there are low ATP levels, there is ______ in cell integrity and ____ pumps and mechanisms to maintain low intracellular ____.
breakdown
Na/K
Ca++
When _______ pumps fail–>delpolarizes cell membranes—>____________ release—>binds to _____ receptors—>____ influx into cell—>cerebral edema, ischemia, microvascular damange w/resultant necrosis
Na/K
Glutamate release
NMDA
Ca++
T/F: there is normal cerebral metabolism during the Latency phase.
True
Secondary phase is characterized by (4 things)
- Ongoing energy failure (supply can not meet demand)
- Excitotoxicity injury (glutamate-excitatory AA–ok in regulated amts)
- Cytokine injury
- Oxidative stress
_______ is the primary type of cell death in the secondary phase.
Apoptosis
T/F: In the secondary phase during excitotoxicity injury, Glutamate binds w/NMDA receptor which worsens Ca++ influx into cells.
True
Ca++ influx–> inflammatory process in the ______.
brain
Free radicals are formed in the breakdown of the ____ ________.
cell membranes
What are free radicals?
Molecules w/unpaired electrons–they initiate reactions that cause cell damage
T/F: Free radicals can cause breakdown of the BBB?
True
T/F: Free radicals can affect blood cells including platelets so clotting doesn’t work as well. WBC’s accumulate in the brain instead of circulating the site of injury.
True
What 3 things do free radicals do?
- Leakage of BBB
- Change platelet function
- Neutrophil accumulation
WHat 3 proinflammatory cytokines are activated and have nuerotoxic properties?
TNF Alpha
IL1B
IL8
What is Apoptosis?
When does it occur?
Characterized by?
Programmed cell death
Following the injury days-weeks
Cell shrinking, preservation of cell membrane, death w/o inflammation
T/F: when in development HIE occurs matters
True
In term infants with HIE, the _______ (functional cells of the brain) and gray nuclei are most vulnerable.
Neurons
In preterm infants with HIE, the ___________ are vulnerable to hypoxic injury –> white matter dz–>____.
Oligodendrocytes
PVL
If you have HIE at < 20 wks, you can have what?
Abnormal migration of brain tissue
If you have HIE at 26-36 wks GA, you will have what?
PVL
If you have HIE >36 wks, you will have what?
Deep gray matter/watershed areas injured
What area of the brain has the most tenuous blood supply?
Watershed areas—needs the most optimal blood flow to be perfused
The _____ ______ along with ____ _____ controls motor
Basal ganglia
Motor Cortex
Communication run via the ______________
Thalamus
There is a ____ hr window for initiating hypothermia.
6
Cooling tx of HIE works to: 4 things
- decrease tissue metabolic demand
- Decrease calcium influx into neuronal cells
- Reduce free radicals
- Attenuates pro-inflammatory cascade
You can see what VS change in a baby with increasingly severe HIE
Bradycardia
What is important to assess in a baby w/HIE?
Primitive reflexes (they are preserved even in the presence of severe injury)
The optimal Rectal/core temp during cooling=?
33-34 degrees C
What is the minimum age for cooling?
36 wks GA
How do you decide who to cool?
- > 36 wks
- APGAR <5 at 10 min
- Continued need for resuscitation: ETT/PPV at 10 min
- Acidosis (pH <7, Base def >16 w/in 60 min birth)
- Mod-severe HIE w/altered LOC (lethargy/stupor/coma) AND 1 of: Hypotonia, abnormal reflexes, weak/absent suck, clinical seizures
- EEG for 20 min shows abnormal background or seizures
What are contraindications to cooling? 6 things
- <36 wks GA
- > 6 hrs life
- coagulopathy w/ACTIVE bleeding
- Prenatal dx of syndrome/do not compatible w/life
- head trauma/ICH
- BW <1800 gms
What labs to obtain pre-cooling:
- ABG and cord gas
- BMP (follow lytes and renal fxn)
- Troponin (heart)
- AST/ALT (liver)
- PT/PTT (coags)
- CBC
- Ammonia (r/o underlying metabolic dz)
What is very common and a Hallmark of HIE?
End organ dysfunction
-up to 70% have renal impairment
What imaging would you want pre-cooling
- HUS (critical to r/o big bleed 1st)
2. CXR
What would you want during cooling?
EEG to monitor for subclinical seizures (entire 72 hrs so you can tx if needed)
Neurology consult
Medication metabolism (may be altered)
Hyperglycemia
QT prolongation (w/bradycardia, check this out)
Coagulation abnormalities
How fast do you re-warm?
0.5 degrees/hr
Why do you want slow vs. fast re-warm?
Fast is not good for cellular functioning
What imaging do you want 1 wk after cooling?
MRI
