1. THERMOREGULATION IN THE NEONATE
Mary
DeBarbieris, RNC
October, 2008

2. Why Worry About Thermoregulation?
Body temperature is one of the primary vital signs. In terms of ABC’s think: A - Airway B - Breathing C - Circulation D - Degrees

3. Goal of Thermoregulation
Maintain correct body temperature range in order to:
maximize metabolic efficiency
reduce oxygen use
protect enzyme function
reduce calorie expenditure

4. Challenges of thermoregulation in Neonatal care
Prior to delivery infants do not maintain temperature independently
Infant’s in-utero temp is generally 0.5˚C higher than mother’s temp
Rapid cooling occurs after delivery

5. Neurologic adaptation: Thermoregulation
Maintenance of body temp is a major task
Skin is thin & blood vessels are close to the surface
Have little subcutaneous fat to serve as barrier to heat loss
Term Infants have 3x the surface to body mass of an adult
Preterm infants and SGA infants have 4x the surface mass to body mass of an adult
Preterm infants are especially susceptible to heat loss due to poor tone,  fat and thinner skin than term infants

6. Definitions To understand the role of thermoregulation in the care of
infants, we need to
understand a few
simple definitions.

7. Neutral Thermal Temperature
A neutral thermal temperature is
the body temperature at which an
individual's oxygen use and energy
expenditure are minimized.
Minimal metabolic rate
Minimal oxygen consumption

8. Body temperature in the newborn infant
Classification of hypothermia is based on core temperature
NORMAL – to 37.3˚C (97.7 –99.2˚F)
Cold Stress to 36.4˚C (96.8 – 97.6 ˚F)
Cause for concern
Moderate hypothermia 32 –35.9˚C ( ˚F)
Danger, warm infant
Severe hypothermia – below 32˚C (89.6 ˚F)
Outlook grave, skilled care urgently needed

9. Neutral Thermal Environment (NTE)
The air temperature
surrounding the baby
supports maintenance
of a neutral thermal
body temperature.

10. Thermoneutrality When the air temperature is in the correct range and
the infant’s body maintains
a neutral thermal
temperature, we have
achieved thermoneutrality

11. Why Are Infants At Greater Risk for Thermoregulation Problems?

12. Thermoregulation Risk Factors
Premature
SGA
Neuro problems
Endocrine
Cardiac / respiratory problems
Large open areas in the skin
Sedated Infants
Drug exposure

13. Why are they at Risk??? Brown Adipose Tissue Body surface area SQ Fat
Glycogen stores
Body water content
Posture
Hypoxia
Hypoglycemia
Anomalies
CNS
Sedation

14. What Do We Know? Infants have more skin surface per
pound of body weight than older
children or adults
More skin means more radiant heat and more insensible water loss.

15. Risk factors for Preterm Infants
less brown fat and glycogen stores
decreased ability to maintain flexion
increased body surface area compared to weight

16. What Do We Know? The majority of an infant’s
thermal receptors are found
in the face, neck, and shoulder
area.
Stimulation of these
receptors will result in chilling
and calorie expenditure

17. What Do We Know? Shivering, which is the main way in which older
children and adults
generate heat, is
impossible or not
effective in infants.
Neonates and young
infants generate heat by
burning brown fat.

18. What do we know? Physiologic response to hypothermia
Temperature regulation controlled by hypothalamus
Activates norepinephrine release triggering
Pulmonary and peripheral vasoconstriction
Increased pulmonary vascular resistance

19. Production of Heat Metabolic Processes Voluntary Muscle Activity
Peripheral Vasoconstriction
Nonshivering Thermogenesis

20. Metabolic Process Heat Generation by Metabolic Energy
Oxidative metabolism
Glucose
Fats
Protein
Metabolic Energy
Brain
Heart
Adrenal Gland

21. Voluntary Muscle Activity
Postural changes
Restless movements
Limited use to Newborn

22. Peripheral Vasoconstriction
Reduces skin blood flow
Decreases loss of heat from the body

23. Nonshivering Thermogenesis
Metabolism of brown adipose tissue
Initiated in hypothalamus
Sympathetic nervous system
Norepinephrine release at the site of brown fat

24. What is Brown Fat? Brown fat is an energy source for infants
It can be found:
Near Kidneys and adrenals
Neck, mediastinum, scapular,
and the axilla areas.
Can not be replaced once used

26. Brown Fat
In full term infants brown fat is 4 % -10% of adipose deposits.
In preterm infants, brown fat will not be found until weeks gestation, and then only in small amounts.
Brown fat generally disappears 3-6 months after birth, except in cold stressed infants (where it will disappear sooner.)
Hypoxia causes impairment of brown fat metabolism

27. So What? When the air temperature around the baby is cool,
thermoreceptors in the
skin are stimulated. Non-
shivering thermogenesis
is initiated and brown fat is
burned for energy to keep
the body temperature stable.
This is the infant’s initial response.

28. What Next? Conversion of brown fat uses oxygen and glucose,
therefore, the cold stressed
infant will become hypoxic
and hypoglycemic.
Blood gas and glucose levels
are affected.
Growth is affected as calories
are used to stay warm
rather than grow.

29. What are the Signs and Symptoms of Thermal Instability?

30. Methods of heat loss Peripheral Vasodilatation Sweating  blood flow
facilitates heat transfer from periphery
to environment
Sweating
 evaporative heat loss
 postnatal age increases the ability to sweat
Appears first on term newborn head

31. Healthy Vs. Sick Neonate
Healthy Newborn
Brown adipose tissue
Produces heat and loses heat as needed
Sick or Low birth wt infants
Increased energy demand
Decreased energy store
Vulnerable to heat stress

32. Hypothermia – Signs/symptoms
Body cool to touch
Mottling or pallor
Central cyanosis
Acrocyanosis
Poor Feeding
Abdominal distension
Hypotonia
Hypoglycemia
gastric residuals
Bradycardia
Tachypnea
Restlessness
Shallow or Irregular Respirations
Apnea
Lethargy

33. Signs and Symptoms of Hypothermia in Infants
Vasoconstriction
Peripheral vasoconstriction occurs in an effort to limit heat loss via blood vessels close to the skin surface.
Pallor and cool skin may be noted, due to poor peripheral perfusion

34. Signs and Symptoms of Hypothermia in Infants
Increased Respiratory Rate
Pulmonary vasoconstriction occurs secondary to metabolic acidosis.
Increasing Respiratory Distress
Related to decreased surfactant
production, hypoxia, & acidosis

35. Signs and Symptoms of Hypothermia in Infants
Restlessness
Restlessness may be a type of behavioral thermoregulation used to generate heat through muscle movement.
The first sign may be an alteration in sleep patterns.
Restlessness also indicates a change in
mental status as cerebral blood flow
diminishes, due to vasoconstriction.

36. Signs and Symptoms of Hypothermia in Infants
Lethargy
If thermo-instability goes unrecognized, the infant will become more lethargic, as cerebral blood flow continues to diminish and hypoxemia and hypoglycemia become more pronounced.

37. Signs and Symptoms of Hypothermia cont.
Metabolic Disturbances
Metabolic acidosis
Hypoxemia
Hypoglycemia
progress due to continued metabolism of brown fat, release of fatty acids and anaerobic metabolism (lactic acid)

38. Signs and Symptoms of Hypothermia
Cardiac
As central blood volume increases, initially the heart rate and blood pressure increase
Arrhythmias
May result from depressed myocardial contractility and irritability caused by hypothermia

39. Signs and Symptoms of Hypothermia
Poor Feeding/Weight Loss
Poor weight gain occurs
when:
calories consumed
brown fat stores are used to make body heat.

40. Even the smallest
weight loss may take days or even weeks to recover, as infants
are limited in the
volume of food they
can eat and number
of calories they can
tolerate.

41. Consequences of Hypothermia
Hypoxemia from  Oxygen consumption
Hypoglycemia from  glucose metabolism
Respiratory & metabolic acidosis secondary to anaerobic metabolism
Inhibition of surfactant production related to  acidosis

42. Consequences of Hypothermia
 pulmonary blood flow related to pulmonary vasoconstriction in response to  body temperature
 pulmonary vascular resistance compromises the delivery of oxygen at the cell level
 risk of developing PPHN in the near term, term or post term infant

43. Prevention of Hypothermia
Hypothermia can be prevented by maintaining a neutral thermal environment and reducing heat loss.
A neonate is in a neutral thermal environment when the axillary temperature remains at 36.5° ° (97.7° ° F) with minimal oxygen and calorie consumption

44. Prevention of Hypothermia
Reduction of heat loss
Consider the four ways by which the neonate experiences heat loss and intervene appropriately.

45. Prevention of Hypothermia
Prevention of hypothermia is the best treatment but if it occurs anyway, the following is a list of what you can do to relieve the cold stress.
Increase ambient air temperature
Apply external heat sources
Warm hat
Warm blankets or diapers
Chemical mattress

46. Prevention of Hypothermia
Avoid stressing the baby
Monitor skin temperature carefully and when it normalizes remove the external heat sources one at a time to prevent rebound hypothermia

47. Hyperthermia

48. Hyperthermia
HYPERTHERMIA also has negative consequences for the neonate.
Defined as a rectal / axillary temperature greater than 37.3°c (99.2°F)

49. Risk factors for Hyperthermia
Excessive environmental temp
Sepsis
Dehydration
Alterations in the hypothalamic control mechanism
Birth Trauma
Anomalies
Drugs

50. Signs of Hyperthermia Tachypnea Apnea Tachycardia Flushing Hypotension
Irritability
Poor Feeding
Skin Temp > Core Temp

51. Consequences of Hyperthermia
 in Metabolic rate
 oxygen consumption
Dehydration from  insensible water loss
Peripheral vasodilatation/ hypotension
Fluid, electrolyte abnormalities
seizures

52. There Are a Lot of Factors to Consider
There Are a Lot of Factors to Consider. How Can I Be Sure My Patient Maintains Thermoneutrality?

53. It Is Important to Review and Understand the Four Methods of Heat Transfer

55. Convection and Radiation
Occurs when air flow
carries heat to or
away from the body
Radiation
Radiant energy
exchange occurs
between two objects
that are not in direct
contact with
each other.

56. Conduction and Evaporation
Occurs when liquid
is turned to vapor,
as with
amniotic
fluid on a
newly delivered
infant.
Conduction
Heat exchange that
occurs between
objects that are in
direct contact
with one
another

57. Possible Sources of Heat Loss

59. Strategies to prevent heat loss:
CONVECTIVE HEAT LOSS can be prevented by:
Providing warm ambient air temperature
Placing infants less than 1500 grams in incubators
Keeping portholes of the incubator closed
Warming all inspired oxygen
On open warmers keeping sides up and covering infant if possible
Using Infant Servo Temperature Control

60. Strategies to prevent heat loss:
RADIANT HEAT LOSS can be prevented by:
Avoiding placement of incubators, warming tables and bassinets near cold windows, walls, air conditioners, etc..
Placing a knit hat on the infant’s head
Wrapping tiny babies in saran or “bubble” wrap
 environmental temperature

61. Strategies to prevent heat loss:
CONDUCTIVE HEAT LOSS can be prevented by:
Placing a warm diaper or blanket between the neonate and cold surfaces
Placing infant on pre-warmed table at time of delivery
Warming all objects that come in contact with the neonate
Admitting infant to a pre-warmed
Skin to skin contact

62. Strategies to prevent heat loss:
EVAPORATIVE HEAT LOSS can be prevented by:
Keeping the neonate and his/her environment dry.
Drying the baby immediately after delivery.
Placing preterm or SGA infant in occlusive wrap/bag at delivery
Delay bath until temperature is stable

64. Interventions for at Risk Infants
Pre-warmed radiant warmer bed
Pre-warmed incubator
Do not leave a warmer bed or incubator in the manual mode
Servo mode allows the baby to control the heat output of the warmer units
Heated water pad
Heat lamp
Warm and humidify inspired gases
Occlusive wrap/bag at delivery

65. Interventions for at Risk Infants
Open incubator portholes and doors only when necessary
Blanket over incubator
Cluster care

66. Use of Skin Servo Monitoring
Incubators and radiant warmers are designed to work using skin temperature to regulate the thermal environment
As temperature is higher in brown fat areas, avoid placing the temperature probe over brown fat deposit areas, such as the axilla, neck, or back.

67. Skin servo control
If the temperature probe is placed over brown fat deposit areas, the probe will be reading a core body temperature and not a skin temperature.
As the core temperature will be higher than the skin temp., the warming
device will cool the environment.
The infant will then need to burn
fat and calories to stay warm

68. Temperature Probe Placement
Secure the temperature probe at/or about
the costal margin of the chest, midway
between the xiphoid and the navel. This
placement should assure accurate skin
temperature measurement.
Never lay infants on the probe, as this will also cause a falsely high temperature to be registered.

69. Skin temperature Probes
Do Not lay infant on skin probe
Do not place over:
Bony prominences
Areas of brown fat deposits
Poorly vascular areas
Excoriated areas
Keep probe exposed to heat source
Keep probe securely attached

70. Safety Considerations
Make sure the sides of radiant warmers are up, unless medically unable.
This protects the infant from air currents in the room that might stimulate thermal receptors.

71. Interventions to Consider
Cover thermoreceptor-rich areas, such as the head.
Dry well after baths, especially the head and neck area.
Dress and cover infants, when in cribs, to prevent them from chilling.
Warm fluids prior to dressing changes
Rewarm slowly to prevent a potential subsequent drop in blood pressure.

72. Rewarming the Hypothermic Infant
Always be prepared to intervene
Rewarm slowly (0.5˚C per hour)
Monitor closely (vital signs every 15 – 30min)
Core temp
Skin temp will be higher than axillary
Blood pressure
Rewarming may lead to vasodilation - hypotension
Heart rate and rhythm
Bradycardia & arrhythmias common with hypothermia

73. Rewarming Monitor Respiratory rate and effort Oxygen saturations
Increased distress
Apnea
Oxygen saturations
Hypoxemia / desaturations
Be prepared for  need for respiratory support
Monitor acid/base status
Blood glucose
Monitor- infant at increase risk for hypoglycemia

74. Guidelines for Rewarming
Incubator better control than warmer
Set temp 1 – 1.5˚C above core temp
Assess infant temp every minutes
As infants core temp reaches set temp and infant is not showing signs of deterioration increase set temp again.
Continue process until temp within normal range

75. Signs of Deterioration during rewarming
Tachycardia – due to in cardiac output
Cardiac arrhythmia
Hypotension
Hypoxemia / Desaturations
Worsening respiratory distress
Worsening acidosis

76. Cooling the overheated neonate
Extended position- not flexed
Expose skin- remove clothing
Keep active temp reduction methods to a minimum to prevent dramatic heat loss
Monitor temperature and VS every 15 – 30minutes
Be prepared to intervene

77. Preparing bag for delivery

80. Key Points to Know in Preventing Hypothermia
Infant most vulnerable
Premature and SGA infants
Neonates requiring prolonged resuscitation
Acutely ill
Open skin defects (abdomen, spine)
Remember the basics
Warm, humidified oxygen ASAP
Warm objects before contact with infant
Pre warmed Radiant warmer/incubator – utilize servo control
Rewarm cautiously- Be prepared to resuscitate

81. Conclusions
Hypothermia in the newborn is due more to a lack of knowledge than to lack of equipment.
Hypothermia is a preventable condition that has well documented impact on morbidity and mortality.
Therefore, assisting the infant to maintain a normal body temperature and preventing hypothermia during stabilization is critical

82. Thank you.