Thermoregulation Flashcards
Neutral Thermal Environment (NTE)
Infants are in a neutral thermal environment when they do not need to use energy to maintain their body temperatures
Non-Shivering Thermogenesis (NST)
The primary way term neonates respond to cold stress is through the oxidation of brown fat to create heat (NST)
When does brown fat production begin in the fetus?
26-28 weeks gestation
Where is brown fat found?
Babies have a patch of brown fat between their shoulder blades, around their head and neck, in their axilla, and around their adrenal glands
What hormone is released in response to cold stress?
Norepinephrine; the release of norepinephrine directs brown fat cells to generate energy and produce heat in the body’s core regions
What are the 4 mechanisms of heat transfer?
Conduction, Convection, Evaporation, Radiation
Conduction
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)
Convection
The transfer of heat to the air moving around and across the body (avoid drafts/vents with an isolette, use humidified oxygen)
Evaporation
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)
Radiation
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)
Why is an immature stratum corneum a risk for ELBW neonates?
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
What is the appropriate humidity level for ELBW neonates to eliminate evaporative heat loss?
70-90% for the first 7 days, then 40% to allow for skin barrier development
Signs and symptoms of hypothermia
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
What temperature does NRP recommend having the delivery room at for the birth of an ELBW neonate?
23-25C, 74-77F
What does NRP recommend for use in all neonates born <32 weeks to maintain heat?
Plastic wrap and heated mattress
How quickly should you rewarm a hypothermic neonate?
0.5-1 degree C or 0.9-1.4 degree F per hour until normal temperature is reached
What are important ways to manage hypothermia in the preterm neonate?
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
What are the 3 methods to heat production in the ELBW neonate?
- Activity/Tone
- Involuntary Activity
- Non-Shivering Thermogenesis (NST)
List 7 factors that contribute to an ELBW neonate’s vulnerability to thermal stress
- Limited stores of metabolic substrates
- Vasomotor immaturity (vessels don’t constrict when cold to retain heat)
- Greater surface area-to-weight ratio
- Immature skin integrity
- Immature CNS delays response to cold stress
- Heat production requires oxygen consumption
- Behavioral factors
What part of the brain controls thermoregulation?
Hypothalamus (controls body temperature, hunger, fatigue, sleep, and circadian rhythm)
What type of heat loss are you preventing if you rapidly dry the baby after birth and apply plastic wrap?
Evaporation
What type of heat loss are you preventing if you make sure the isolette is warmer than the baby’s temperature?
Radiation
What type of heat loss are you preventing if you pre-warm the stethoscope before touching it to the baby’s skin?
Conduction
What type of heat loss are you preventing if you use humidified oxygen in ELBW neonates?
Convection
List some common symptoms related to each body system of cold stress hypothermia
CV: acrocyanosis, mottling, poor perfusion
Respiratory: apnea, oxygen needs
CNS: lethargy, hypotonia, seizures
GI: increased residuals/poor feeding
List some common symptoms of hyperthermia
Tachycardia Tachypnea Hypotension Dehydration Seizure activity Apnea Poor feeding/weight gain Increased oxygen needs
What effect on metabolic rate and subsequent oxygen consumption do both hypo- and hyperthermia have?
Both can increase metabolic rate, which increases oxygen consumption
List 4 advantages to using an isolette
Provides a controlled thermal environment, minimizes evaporative and convective heat loss, available in air and servo modes, offers neuroprotective environment
