Flashcards in Thermoregulation Deck (62)
What is the neutral thermal environment?
an environment that is able to regulate heat production using minimal amounts of oxygen and glucose; the maintenance of a delicate balance between heat production and heat loss
What is the risk to the NTE at delivery?
an infant's temp can drop 2-3degrees, putting the babe at risk for hypothermia with resultant hypoglycemia, neurologic sequelae and death
What is a neonate's normal core temperature?
What are the classifications of hypothermia?
mild, moderate and severe
How is mild hypothermia defined?
How is moderate hypothermia defined?
How is severe hypothermia defined?
In 1995, Beeram et al reported what consequences were a/w hypothermia?
an 11 fold increase in infant mortality when infants were born; hypothermia found in 60% of non-surviving infants
In 1999, Hulsey reported what neurologic implications a/w hypothermia?
surviving hypothermic infants had significantly more CNS disorders and rates of IVH
What are risk factors for temperature instability?
SGA, preterm, CNS abnormalities/damage, endocrine problems, hypoglycemia, cardiorespiratory abnormalities, abdominal wall defects, neuromuscular abnormalities, sepsis and spinal defects
How developed is shivering thermogenesis in the newborn?
very poorly developed
What is non-shivering thermogenesis?
metabolic pathway that is the main method of heat production for the newborn- utilizes brown fat metabolism
What is the only fx of brown fat?
to produce heat
What is required in the process of non-shivering thermogenesis?
O2 and glucose- this is why thermoregulation, a normal glucose level and adequate oxygenation are so closely linked
What is thermostability?
in an optimal situation, the newborn will maintain their core temp WNL within a wide range of ambient temp variation without increased O2 consumption or increased metabolic rate
Where is brown fat located?
axilla, nape of the neck, between the scapulas, mediastinum and around the kidneys
When do brown fat stores increase postnatally?
increase until 3-5 weeks postnatal life
What is the mechanism for non-shivering thermogenesis?
with the onset of cold stress, the hypothalamus detects this state and secretes epinephrine to produce vasoconstriction and to signal brown fat metabolism
What is responsible for temperature control?
What is the body's method for regulating against hyperthermia?
peripheral vasodilation to allow heat to reach the skin's surface, also results in insensible water losses that allows for the dissipation of heat; respiratory center is stimulated to increase RR to release heat via the lungs
What are the mechanisms for heat transfer?
conduction, convection, evaporation and radiation
What is conduction?
heat transfer by direct contact; degree of heat loss varies with exposed surface area
What factors increase an infant's risk to heat loss via conduction?
decreased ability to flex extremities, decreased subQ fat and limited ability to vasoconstrictor peripheral blood vessels
How can heat loss via conduction be minimized?
swaddling, skin to skin, prewar all equipment before contact with infant's skin
What is convection?
heat loss from air current that move heat away from the body; affected by ambient temperature, air flow velocity and relative humidity
How can heat loss via convection be accelerated?
when the environmental temperature is cooler and/or air flow velocity is higher
What are common ways that neonates loose heat via convection?
heat is swept away by drafts, air currents, AC, doors, windows, fans, open incubator portholes or "traffic" around the baby's bed
How can heat loss via convection be minimized?
keep warmer sides up, cover with plastic, tx in preheated warmers, warm and humidify O2 prior to use, use incubator, move beds away from drafts or vents, dress and swaddle baby in pre warmed linens
What is evaporation?
liquid in converted into vapor, major source of heat loss at delivery and with bathing; heat is lost through the skin and respiratory tract (insensible water loss)