Hypothermia For HIE

Question 1

Provide an overview of the pathophysiology of HIE

Answer 1

2 phases of energy failure:
1. Primary phase: decreased cerebral blood flow ➡️ hypoxia.
⏩⏩ calcium enters cell, cell edema and necrosis

Resuscitation. Reperfusion.

Latent period with normalisation of oxidative metabolism

2. Secondary phase: develops at 12-36 hours. Can last 14 days!
   Failure of intercellular energy processes
   ⏩⏩free radicals and cell death

Question 2

How long is the latent phase

Answer 2

6-12 hours

Question 3

What are the details of the primary phase?

Answer 3

Primary phase: decreased cerebral blood flow ➡️ hypoxia.

• decrease ATP available
• Na/K pumps fail

➡️ cellular depolarisation, lactic acid, release of excitatory amino acids

➡️➡️ calcium enters cell, cell edema and necrosis

Question 4

Describe the secondary phase in detail

How long does it last?

Answer 4

Secondary phase: develops at 12-36 hours. Can last 14 days!

Failure of intercellular energy processes:
-mitochondrial failure

AND

Accumulation of bad shit:

• free radicals
• excitatory amino acids
• cytotoxic edema

⏩⏩ initiation of apoptosis and cell death

Question 5

How does therapeutic hypothermia work?

Answer 5

WORKS ON SECONDARY PHASE

• amelioration of apoptosis
• decrease loss of high energy phosphates
• decrease oxygen consumption
• reduces NO, glutamate, free radicals and excitatory amino acids
• induces genes that inhibit cell death

Question 6

What are the different ways of achieving therapeutic hypothermia?

(2)

Answer 6

Selective head cooling with mild systemic cooling

Whole body cooling

Question 7

Does therapeutic hypothermia work?

Answer 7

Yes

Decreases death and disability

Question 8

Who do you not cool?

5-6

Answer 8

Preterm 
Trauma 
Intracranial bleeds 
> 6 hours
Very severe encephalopathy 
Genetic or congenial anomalies

Question 9

Who do you cool?

Answer 9

Must be term

AND

Evidence of stress: APGAR 5 at 10 min, resus ongoing at 10 min or cord gas with BE >16 or PH

Question 10

What investigation can help you decide re cooling?

Answer 10

EEG

Question 11

Risks of hypothermia, in general (5) and with head cooling (2)

Answer 11

Arrhythmias
Bradycardia
Hypotension 
Thrombocytopenia 
Bleeding diathesis

Scalp oedema
Skin breakdown

Question 12

How low do you go

Answer 12

34 +- 0.5

Question 13

How long do you cool for?

Answer 13

48-72 hours

Question 14

How fast do you rewarm

Answer 14

0.5 every 1-4 hours

Question 15

What follow up do these kids need?

Answer 15

At 18 and 24 months
MDT
motor, psychoeducational, auditory and cognitive

Question 16

What are the SARNAT criteria?

Answer 16

S -  SEIZURES+ EEG
o	Seizures: none, common, uncommon 
o	EEG: Mild, moderate and severe depression 
A - ACTIVITY(spontaneous)
o	normal, decreased or none
R - REFLEXES (primitive)
o	Suck: weak, absent, absent
o	Moro: strong, weak, absent
o	oculovestibular: normal, overactive, absent
N - NEURO
o	Tone: normal, hypotonia, flacid
o	Posture: distal flexion, strong distal flexion, decerebrate
o	DTR: overactive, overactive, absent
o	Myoclonus
A - AUTOMATIC
o	Pupils: mydriais, miosis, nonreactive
o	HR: tachy, brady, variable
o	Respiration: normal, periodic, apnea
o	Secretions: sparse: profuse, variable
T - TALKCATIVE: level of conscious 
o	Hyper alert, lethargic, coma

Question 17

What is the incidence of HIE

Answer 17

1/1000 - 6/1000