HIE Flashcards
What is the incidence of HIE?
1/1000-1/6000 live births
What is the mechanism of brain injury in HIE?
Impaired perfusion in the setting of hypoxia
What is the mechanism of protection of cooling in HIE?
- Broad inhibitory activity against harmful cell processes
- Amelioration of apoptosis
- Decreased loss of high energy [hotphates
- Reduced oxygen consumption
- Reduced release of nitric oxide, glutamae, free radicals, excitatory amino acids
- Induction of genes that reduce neuronal death
What is the evidence for cooling in HIE?
Cochrane review analyzed 8 studies of cooling and showed hypothermia reduced the combined outcome of mortality or major neurodevelopmental disability at 18 months (RR 0.76), reduced mortality (RR 0.74) and reduced neurodevelopmental disability (RR 0.68)
Should hypothermia be routinely offered to infants with HIE?
- Only available neuroprotective treatment for HIE and considered the standard of care for mod-severe HIE
- Less beneficial for babies with severe encephalopathy - Use may delay end of life decision making for babies with an extremely poor prognosis
Which infants should be treated with hypothermia?
- > 36 weeks GA
- < 6 hours old
- Meet both criteria A and B:
- Criteria A - any 2 of the following:
- Apgar < 5 at 10 min
- Continued need for ventilation and resuscitation at 10 mins
- Metabolic acidosis with pH < 7 or base deficit > 16mmol/L in cord or arterial blood gases measured within 1h of birth
- Criteria B
- Moderate (Sarnat stage II) or severe (Sarnat stage III) encephalopathy demonstrated by seizures or at least one sign in at least 3/6 categories
- Criteria A - any 2 of the following:
What are the characteristics of mild HIE?
LOC
Spontaneous activity
Neuromuscular control: tone, posture, stretch reflexes, segmental myoclonus
Primary reflexes: suck, moro, oculovestibular
ANS: pupils, HR, RR, secretions
Seizures
EEG
- LOC: hyperalert
- Spontaneous activity: normal
- Tone: normal
- Posture: mild distal flexion
- Stretch reflexes: overactive
- Segmental myoclonus: present
- Suck: weak
- Moro: strong
- Oculovestibular: normal
- ANS: sympathetic
- Pupils: mydriasis
- HR: tachycardic
- RR: normal
- Secretions: sparse
- Seizures: none
- EEG: mild depression
What are the characteristics of moderate HIE?
LOC
Spontaneous activity
Neuromuscular control: tone, posture, stretch reflexes, segmental myoclonus
Primary reflexes: suck, moro, oculovestibular
ANS: pupils, HR, RR, secretions
Seizures
EEG
LOC: lethargic
Spontaneous activity: decreased
Tone: mild hypotonia
Posture: strong distal flexion
Stretch reflexes: overactive
Segmental myoclonus: present
Suck: weak/absent
Moro: weak
Oculovestibular: overactive
ANS: parasympathetic
Pupils: miosis
HR: bradycardic
RR: periodic
Secretions: profuse
Seizures: common
EEG: moderate depression
What are the characteristics of severe HIE?
LOC
Spontaneous activity
Neuromuscular control: tone, posture, stretch reflexes, segmental myoclonus
Primary reflexes: suck, moro, oculovestibular
ANS: pupils, HR, RR, secretions
Seizures
EEG
LOC: stupor/coma
Spontaneous activity: none
Tone: flaccid
Posture: decerebrate
Stretch reflexes: absent
Segmental myoclonus: absent
Suck: absent
Moro: absent
Oculovestibular: absent
ANS: both ANS and PNS absent
Pupils: nonreactive
HR: variable
RR: apnea
Secretions: variable
Seizures: uncommon
EEG: severe depression
Where should hypothermia be provided and why?
- Level III NICU
- To treat multiorgan dysfcuntion associated with cooling and possible complications of cooling
What are possible complications of cooling?
- Cardiac arrythmias
- Bleeding diathesis
Which infants should not be routinely cooled?
- Severe head trauma
- Intracranial bleeding
- Infants < 36 weeks
- Infants > 6 hours
- Careful with: severe encaphalopathy, congenital anomalies, abnormal chromosomes
What are the drawbacks of selective head cooling?
- Expensive and labour intensive
- Can produce scalp edema or skin breakdown
- More difficult to maintain rectal temps
- Limites access foe EEGs
What are the advantages of total body cooling?
- Easier to use
- Less expensive
- Access to EEG
- More likely to be available in the hospital
- Used in 65% of cases in one survey
What is the optimal temperature?
- 34 +/- 0.5 degrees C
