Thermoregulation

Question 1

What is the neutral thermal environment?

Answer 1

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

Question 2

What is the risk to the NTE at delivery?

Answer 2

an infant’s temp can drop 2-3degrees, putting the babe at risk for hypothermia with resultant hypoglycemia, neurologic sequelae and death

Question 3

What is a neonate’s normal core temperature?

Answer 3

97.7-99.5

Question 4

What are the classifications of hypothermia?

Answer 4

mild, moderate and severe

Question 5

How is mild hypothermia defined?

Answer 5

96.8-97.6

Question 6

How is moderate hypothermia defined?

Answer 6

89.6-96.6

Question 7

How is severe hypothermia defined?

Answer 7

<89.6

Question 8

In 1995, Beeram et al reported what consequences were a/w hypothermia?

Answer 8

an 11 fold increase in infant mortality when infants were born; hypothermia found in 60% of non-surviving infants

Question 9

In 1999, Hulsey reported what neurologic implications a/w hypothermia?

Answer 9

surviving hypothermic infants had significantly more CNS disorders and rates of IVH

Question 10

What are risk factors for temperature instability?

Answer 10

SGA, preterm, CNS abnormalities/damage, endocrine problems, hypoglycemia, cardiorespiratory abnormalities, abdominal wall defects, neuromuscular abnormalities, sepsis and spinal defects

Question 11

How developed is shivering thermogenesis in the newborn?

Answer 11

very poorly developed

Question 12

What is non-shivering thermogenesis?

Answer 12

metabolic pathway that is the main method of heat production for the newborn- utilizes brown fat metabolism

Question 13

What is the only fx of brown fat?

Answer 13

to produce heat

Question 14

What is required in the process of non-shivering thermogenesis?

Answer 14

O2 and glucose- this is why thermoregulation, a normal glucose level and adequate oxygenation are so closely linked

Question 15

What is thermostability?

Answer 15

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

Question 16

Where is brown fat located?

Answer 16

axilla, nape of the neck, between the scapulas, mediastinum and around the kidneys

Question 17

When do brown fat stores increase postnatally?

Answer 17

increase until 3-5 weeks postnatal life

Question 18

What is the mechanism for non-shivering thermogenesis?

Answer 18

with the onset of cold stress, the hypothalamus detects this state and secretes epinephrine to produce vasoconstriction and to signal brown fat metabolism

Question 19

What is responsible for temperature control?

Answer 19

the hypothalamus

Question 20

What is the body’s method for regulating against hyperthermia?

Answer 20

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

Question 21

What are the mechanisms for heat transfer?

Answer 21

conduction, convection, evaporation and radiation

Question 22

What is conduction?

Answer 22

heat transfer by direct contact; degree of heat loss varies with exposed surface area

Question 23

What factors increase an infant’s risk to heat loss via conduction?

Answer 23

decreased ability to flex extremities, decreased subQ fat and limited ability to vasoconstrictor peripheral blood vessels

Question 24

How can heat loss via conduction be minimized?

Answer 24

swaddling, skin to skin, prewar all equipment before contact with infant’s skin

Question 25

What is convection?

Answer 25

heat loss from air current that move heat away from the body; affected by ambient temperature, air flow velocity and relative humidity

Question 26

How can heat loss via convection be accelerated?

Answer 26

when the environmental temperature is cooler and/or air flow velocity is higher

Question 27

What are common ways that neonates loose heat via convection?

Answer 27

heat is swept away by drafts, air currents, AC, doors, windows, fans, open incubator portholes or "traffic" around the baby's bed

Question 28

How can heat loss via convection be minimized?

Answer 28

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

Question 29

What is evaporation?

Answer 29

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)

Question 30

What is heat loss via evaporation dependent upon?

Answer 30

air speed and relative humidity

Question 31

When does heat loss via evaporation occur?

Answer 31

when moisture on the surface of the skin or respiratory tract mucosa is converted into vapor- always accompanied with a cooling effect

Question 32

What facilities heat loss via evaporation?

Answer 32

the cooler the ambient environment, the more rapid the heat loss

Question 33

What is the effect of increasing incubator humidity?

Answer 33

decreases evaporative losses

Question 34

How can heat loss via evaporation be minimized?

Answer 34

drying infant, then removing wet blankets, plastic bags at del, increase room temp, eliminate drafts/vents, heating and humidifying the incubator & O2, warming solutions prior to contact with bb, delay bath until body temp has stabilized

Question 35

What is radiation?

Answer 35

transfer of radiant energy from the body to objects without direct contact

Question 36

How can heat loss via radiation be minimized?

Answer 36

double walled incubators, pre warming the incubator, keeping incubator away from cooler exterior walls and windows, using isolette cover

Question 37

How does radiant warmer heat gain occur?

Answer 37

when the surrounding surfaces are warmer than the infant's skin temperature

Question 38

What is the greenhouse effect?

Answer 38

heat is trapped bc plexiglass walls allow short wave radiation to penetrate the interior, baby will absorb all this short wave heat, but readmits heat as long wave radiation heat which cannot pass through the incubator wall. Long wave heat radiation can be reabsorbed by the infant, and if the cycle is not interrupted, the baby will become hyperthermic (c no incubator temp ∆)

Question 39

What are the advantages of the radiant warmer?

Answer 39

quickly rewarm, allows direct access for procedures

Question 40

What are the disadvantages of the radiant warmer?

Answer 40

risk for thermal burns and hyperthermia- ALWAYS USE ON SERVO MODE

Question 41

What are the advantages of the incubator?

Answer 41

can be used on skin or servo mode, quieter environment, decreases insensible water losses

Question 42

What are the disadvantages of the incubator?

Answer 42

limited access

Question 43

What is the process of weaning an infant to the crib?

Answer 43

based on GA and/or weight; a baby hasn't successfully weaned to the crib if they are wearing excessive amt of clothes

Question 44

What are the benefits of skin to skin?

Answer 44

can be close to the breast for feeding, stabilize VS and oxygenation, improve sleeping patterns and direct social eye contact

Question 45

What are contraindications for skin to skin?

Answer 45

physiologic instability

Question 46

What is the clinical presentation of hypothermia?

Answer 46

pale, cool to the touch, acrocyanosis, respiratory distress, apnea, bradycardia, central cyanosis, irritability progressing into lethargy, progressive or chronic cold stress

Question 47

What is the clinical progression of hypothermia?

Answer 47

progressive, peripheral vasoconstriction is the first response, then O2 consumption will increase, then progresses into A/B/central cyanosis

Question 48

How does an infant present with chronic cold stress?

Answer 48

a weak cry, hypotonia, increased gastric residuals, abdominal dissension, poor feeding and poor weight gain

Question 49

What is the physiologic response to cold stress?

Answer 49

vasoconstriction, brown fat metabolism and increased muscle activity and flexion

Question 50

How will a term infant utilize muscle activity and flexion in a hypothermic state?

Answer 50

a term babe can increase muscles activity to increase heat and flex to decrease the surface area exposed to cooler environmental temperatures

Question 51

How does vasoconstriction affect core body temperature?

Answer 51

shunting blood away from the skin surface into the body core, even with mild hypothermia

Question 52

What happens to the metabolic rate in an infant with hypothermia?

Answer 52

metabolic rate increases in an effort to produce heat and conserve heat which in turn increases O2 consumption and glucose utilization; significant risk of conversion to anaerobic metabolism which will increase lactic acid built up

Question 53

How is the respiratory system affected by hypothermia?

Answer 53

if already experiencing RDS, an increase in O2 demand may worsen distress and lead to hypoxemia

Question 54

What conditions should be included in your differential diagnosis of temperature instability?

Answer 54

sepsis, hypothermia r/t prematurity and inappropriate environment, use of equipment, misuse of equipment

Question 55

What is the recommended rate of rewarming an infant?

Answer 55

rate should be specific to each individual infant- depending on their tolerance; no evidence to give a specific rate; don't exceed 0.5 degrees/hr

Question 56

What should be monitored while rewarming an infant?

Answer 56

vital signs, level of consciousness, acid/base status

Question 57

If utilizing a radiant warmer to rewarm an infant, what should be remembered?

Answer 57

with exposed skin, blood vessels are sensitive to heat (skin warms quicker than core), risk is warmer in response to cold baby temp will operate on full heat output

Question 58

What is the risk of warming an infant too quickly?

Answer 58

rapid heating can cause vasodilation and a rapid drop in BP- if infant's status begins to deteriorate, then the rate of warming needs to be ∆

Question 59

What is the clinical presentation of hyperthermia?

Answer 59

warm to the touch, pink/ruddy (r/t vasodilation), tachypnea, apnea, tachycardia, weak cry, hypotonia, irritable, lethargic, poor feeding, sz, may have perspiration, hypotension

Question 60

What is the etiology of hyperthermia in neonates?

Answer 60

equipment use/misuse, remove iatrogenic etiology- bundling, direct sunlight, phototx, etc; sepsis, CNS abnormalities or dehyradtion

Question 61

What are common complications a/w hyperthermia?

Answer 61

increased insensible water losses, dehyradtion, hypotension and apnea

Question 62

What is the infant's response to hyperthemia?

Answer 62

thermal receptors sense overheating causing peripheral vasodilation and sweating occurs, which increases the evaporative losses