Hypothermia for newborns with hypoxic ischemic encephalopathy Flashcards
What is the incidence of HIE?
1-6/1000 live births
What is the mechanism causing brain injury post intrapartum hypoxia-ischemia?
Impaired cerebral blood flow resulting in two phases of energy failure
Primary phase: reduction in blood flow and O2 supply –> fall in ATP, failure of Na/K pump, depolarization of cells, lactic acidosis, release of excitatory amino acids, calcium entry into cell, and cell necrosis
Resuscitation and reperfusion
Latent period (6-12h) with normalization of oxidative metabolism
Secondary phase (12-36h until 7-14d): initiation of apoptosis, mitochondrial failure, cytotoxic edema, accumulation of excitatory amino acids, release of free radicals, cell death
Which infants should be treated with therapeutic hypothermia?
Infants >36 weeks GA who are <6h of age and meet BOTH criteria A and B:
Criteria A: Any two of the following:
- Apgar score <5 @ 10min of life
- Continued need for ventilation and resuscitation @ 10min of life
- Metabolic acidosis pH <7 or BE >16 in cord or ABG measured within 1h of birth
AND Criteria B:
Moderate (Sarnat stage II) or severe (Sarnat stage III) encephalopathy demonstrated by the presence of seizures or at least one sign in at least 3 of 6 categories
Where should hypothermia be provided?
Level III NICU where resources are available to treat multiorgan failure, cardiac arrhythmias, and bleeding diathesis
Must have:
- US
- CT
- MRI
- EEG
- Neurosensory evoked potential recordings
Consider in community hospitals in consultation with a level III NICU
Which infants should not be routinely cooled?
- Severe head trauma
- Intracranial bleeding
- Infants >6h of age
- Infants < 36wks GA
Consider in:
- Very severe encephalopathy
- Congenital anomalies
- Abnormal chromosomes
What method of cooling should be used?
Total body cooling is easier to use, less expensive, provides access to EEGs, and is more available than selective head cooling which can produce scalp edema or skin breakdown and makes it more difficult to maintain rectal temperature
What is the target temperature to be reached?
Rectal or esophageal temperature 34 +/-0.5 degrees Celsius
What are the clinical criteria for mild encephalopathy?
- LOC: hyperalert
- Spontaneous activity: normal
3. Neuromuscular control Tone: normal Posture: mild distal flexion Stretch reflexes: overactive Segmental myoclonus: present
- Primary reflexes
Suck: weak
Moro: strong
Oculovestibular: normal
5. Autonomic system: sympathetic Pupils: mydriasis HR: tachycardia Resp: normal Secretions: sparse
- Seizures: none
- EEG: mild depression
What are the clinical criteria for moderate encephalopathy?
- LOC: lethargic
- Spontaneous activity: decreased
3. Neuromuscular control Tone: mild hypotonia Posture: strong distal flexion Stretch reflexes: overactive Segmental myoclonus: present
- Primary reflexes
Suck: weak or absent
Moro: weak
Oculovestibular: overactive
5. Autonomic system: parasympathetic Pupils: miosis HR: bradycardia Resp: periodic Secretions: profuse
- Seizures: common
- EEG: moderate depression
What are the clinical criteria for severe encephalopathy?
- LOC: stupor or coma
- Spontaneous activity: none
3. Neuromuscular control Tone: flaccid Posture: decerebrate Stretch reflexes: absent Segmental myoclonus: absent
- Primary reflexes
Suck: absent
Moro: absent
Oculovestibular: absent
5. Autonomic system: both absent Pupils: non-reactive HR: variable Resp: apnea Secretions: variable
- Seizures: uncommon
- EEG: severe depression
How long should cooling last?
Optimal duration is unknown, most use 72h
How should the infant be rewarmed?
Slow re-warming, usu. by 0.5 degrees q2h
What are the side effects of hypothermia?
- Mild bradycardia
- Mild hypotension
- Arrhythmias
- Mild thrombocytopenia
- Sclerema/edema
Can cooling be used in premature infants?
No evidence of benefit in infants <36 wks GA
What is the follow-up for cooled infants?
f/u @ 18-24m with long term f/u of motor, psychoeducational, auditory, and cognitive outcomes
