Thermoregulation

Question 1

Neutral Thermal Environment (NTE)

Answer 1

Infants are in a neutral thermal environment when they do not need to use energy to maintain their body temperatures

Question 2

Non-Shivering Thermogenesis (NST)

Answer 2

The primary way term neonates respond to cold stress is through the oxidation of brown fat to create heat (NST)

Question 3

When does brown fat production begin in the fetus?

Answer 3

26-28 weeks gestation

Question 4

Where is brown fat found?

Answer 4

Babies have a patch of brown fat between their shoulder blades, around their head and neck, in their axilla, and around their adrenal glands

Question 5

What hormone is released in response to cold stress?

Answer 5

Norepinephrine; the release of norepinephrine directs brown fat cells to generate energy and produce heat in the body’s core regions

Question 6

What are the 4 mechanisms of heat transfer?

Answer 6

Conduction, Convection, Evaporation, Radiation

Question 7

Conduction

Answer 7

The transfer of heat between two solid objects in contact with each other whereby the hotter object gives heat to the cooler object (laying baby directly on a scale, touching skin with stethoscope)

Question 8

Convection

Answer 8

The transfer of heat to the air moving around and across the body (avoid drafts/vents with an isolette, use humidified oxygen)

Question 9

Evaporation

Answer 9

The transfer of body heat from the conversion of liquid to vapor (major losses in ELBW neonates through respiratory tract and immature skin - use humidity protocols)

Question 10

Radiation

Answer 10

The transfer of heat between two solid objects not in direct contact with each other (cooler nearby objects may absorb heat from the neonate even when not in direct contact - neonate “radiates” heat to the cooler object)

Question 11

Why is an immature stratum corneum a risk for ELBW neonates?

Answer 11

This becomes a portal for infection and increases risk of toxicity from environmental toxins due to the immature barrier function of the fragile SC with high risk of fluid and electrolyte imbalances and increased TEWL

Question 12

What is the appropriate humidity level for ELBW neonates to eliminate evaporative heat loss?

Answer 12

70-90% for the first 7 days, then 40% to allow for skin barrier development

Question 13

Signs and symptoms of hypothermia

Answer 13

Hypoxia (tachypnea, grunting, flaring, retracting)
- Increased demand for oxygen to maintain temperature may decrease oxygen delivery to tissues and vital organs
Hypoglycemia (lethargy, bradycardia, irritability, apnea, seizures)
- Metabolic rate increases to produce heat and glucose stores are rapidly depleted
Respiratory/Metabolic Acidosis (apnea, seizures, pulmonary hemorrhage)
- Ongoing hypoxia leads to acid-base abnormalities
CV Compromise (tachycardia followed by bradycardia and hypotension)
- Low HR, BP and perfusion with impaired heart contractility and function
Neurologic Compromise (irritability, lethargy)
- Decreased circulation, increased risk of IVH with alterations in cerebral perfusion

Question 14

What temperature does NRP recommend having the delivery room at for the birth of an ELBW neonate?

Answer 14

23-25C, 74-77F

Question 15

What does NRP recommend for use in all neonates born <32 weeks to maintain heat?

Answer 15

Plastic wrap and heated mattress

Question 16

How quickly should you rewarm a hypothermic neonate?

Answer 16

0.5-1 degree C or 0.9-1.4 degree F per hour until normal temperature is reached

Question 17

What are important ways to manage hypothermia in the preterm neonate?

Answer 17

Keep ambient temperature warmer than neonate’s temperature (to avoid heat loss by radiation), use warm IV fluids, pre-warm double-walled isolettes for transport, use plastic and/or thermal mattresses

Question 18

What are the 3 methods to heat production in the ELBW neonate?

Answer 18

1. Activity/Tone
2. Involuntary Activity
3. Non-Shivering Thermogenesis (NST)

Question 19

List 7 factors that contribute to an ELBW neonate’s vulnerability to thermal stress

Answer 19

1. Limited stores of metabolic substrates
2. Vasomotor immaturity (vessels don’t constrict when cold to retain heat)
3. Greater surface area-to-weight ratio
4. Immature skin integrity
5. Immature CNS delays response to cold stress
6. Heat production requires oxygen consumption
7. Behavioral factors

Question 20

What part of the brain controls thermoregulation?

Answer 20

Hypothalamus (controls body temperature, hunger, fatigue, sleep, and circadian rhythm)

Question 21

What type of heat loss are you preventing if you rapidly dry the baby after birth and apply plastic wrap?

Answer 21

Evaporation

Question 22

What type of heat loss are you preventing if you make sure the isolette is warmer than the baby’s temperature?

Answer 22

Radiation

Question 23

What type of heat loss are you preventing if you pre-warm the stethoscope before touching it to the baby’s skin?

Answer 23

Conduction

Question 24

What type of heat loss are you preventing if you use humidified oxygen in ELBW neonates?

Answer 24

Convection

Question 25

List some common symptoms related to each body system of cold stress hypothermia

Answer 25

CV: acrocyanosis, mottling, poor perfusion
Respiratory: apnea, oxygen needs
CNS: lethargy, hypotonia, seizures
GI: increased residuals/poor feeding

Question 26

List some common symptoms of hyperthermia

Answer 26

Tachycardia
Tachypnea
Hypotension
Dehydration
Seizure activity
Apnea
Poor feeding/weight gain
Increased oxygen needs

Question 27

What effect on metabolic rate and subsequent oxygen consumption do both hypo- and hyperthermia have?

Answer 27

Both can increase metabolic rate, which increases oxygen consumption

Question 28

List 4 advantages to using an isolette

Answer 28

Provides a controlled thermal environment, minimizes evaporative and convective heat loss, available in air and servo modes, offers neuroprotective environment