Hypothermia for newborns with hypoxic ischemic encephalopathy Flashcards Preview

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Flashcards in Hypothermia for newborns with hypoxic ischemic encephalopathy Deck (15):
1

What is the incidence of HIE?

1-6/1000 live births

2

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

3

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:
1. Apgar score <5 @ 10min of life
2. Continued need for ventilation and resuscitation @ 10min of life
3. 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

4

Where should hypothermia be provided?

Level III NICU where resources are available to treat multiorgan failure, cardiac arrhythmias, and bleeding diathesis

Must have:
1. US
2. CT
3. MRI
4. EEG
5. Neurosensory evoked potential recordings

Consider in community hospitals in consultation with a level III NICU

5

Which infants should not be routinely cooled?

1. Severe head trauma
2. Intracranial bleeding
3. Infants >6h of age
4. Infants < 36wks GA

Consider in:
5. Very severe encephalopathy
6. Congenital anomalies
7. Abnormal chromosomes

6

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

7

What is the target temperature to be reached?

Rectal or esophageal temperature 34 +/-0.5 degrees Celsius

8

What are the clinical criteria for mild encephalopathy?

1. LOC: hyperalert

2. Spontaneous activity: normal

3. Neuromuscular control
Tone: normal
Posture: mild distal flexion
Stretch reflexes: overactive
Segmental myoclonus: present

4. Primary reflexes
Suck: weak
Moro: strong
Oculovestibular: normal

5. Autonomic system: sympathetic
Pupils: mydriasis
HR: tachycardia
Resp: normal
Secretions: sparse

6. Seizures: none

7. EEG: mild depression

9

What are the clinical criteria for moderate encephalopathy?

1. LOC: lethargic

2. Spontaneous activity: decreased

3. Neuromuscular control
Tone: mild hypotonia
Posture: strong distal flexion
Stretch reflexes: overactive
Segmental myoclonus: present

4. Primary reflexes
Suck: weak or absent
Moro: weak
Oculovestibular: overactive

5. Autonomic system: parasympathetic
Pupils: miosis
HR: bradycardia
Resp: periodic
Secretions: profuse

6. Seizures: common

7. EEG: moderate depression

10

What are the clinical criteria for severe encephalopathy?

1. LOC: stupor or coma

2. Spontaneous activity: none

3. Neuromuscular control
Tone: flaccid
Posture: decerebrate
Stretch reflexes: absent
Segmental myoclonus: absent

4. Primary reflexes
Suck: absent
Moro: absent
Oculovestibular: absent

5. Autonomic system: both absent
Pupils: non-reactive
HR: variable
Resp: apnea
Secretions: variable

6. Seizures: uncommon

7. EEG: severe depression

11

How long should cooling last?

Optimal duration is unknown, most use 72h

12

How should the infant be rewarmed?

Slow re-warming, usu. by 0.5 degrees q2h

13

What are the side effects of hypothermia?

1. Mild bradycardia
2. Mild hypotension
3. Arrhythmias
4. Mild thrombocytopenia
5. Sclerema/edema

14

Can cooling be used in premature infants?

No evidence of benefit in infants <36 wks GA

15

What is the follow-up for cooled infants?

f/u @ 18-24m with long term f/u of motor, psychoeducational, auditory, and cognitive outcomes

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