This document summarizes thermoregulation in newborns. It defines the thermo neutral environment for babies and discusses factors that increase heat loss such as large surface area. It also outlines the major mechanisms of heat production and loss in newborns, including evaporation, conduction, convection, and radiation. Signs and risks of hypothermia and hyperthermia are provided. Prevention of hypothermia is discussed, including steps in the warm chain and use of incubators. Kangaroo mother care is also summarized as an approach to thermoregulation.

1. THERMOREGULATION IN
NEWBORN
Dr. Priyanka (PNB)

2. Thermo neutral environment :
• This is defined as the range of ambient temperature within which the
baby can maintain normal core temperature with minimal metabolic
rate and oxygen consumption by vasomotor activity alone.
• Above and below this temperature, compensatory mechanisms are
necessary to maintain normal temperature.
• In clinical setting, this temperature is regarded as the core
temperature between 36.5°C – 37.5°C and the skin temperature does
not change >0.3°C/hr while measured continuously.

3. • Hyperthermia: Axillary temperature >37.5°C
• Hypothermia: Axillary temperature is <36.5°C
• Cold stress 36.0-36.4°C
• Moderate hypothermia 32-35.9°C
• Severe hypothermia <32°C

4. Frequency of measurement
• Once daily in a term baby
• 2-3 times daily for a small baby (2.4-1.5 kg)
• Four times daily for very small babies (<1.5 kg)
• Every 2 hours for a sick baby
• Frequent assessment by mother using touch should be encouraged.

5. Factors that leads to increase heat losses in
newborn
• large surface area
• transdermal water loss
• limited capacity to change body position
• Incapable of effective shivering
• Environmental temperature
• Using unheated nonhumidified oxygen sources during resuscitation

6. Sources of heat loss
• There are four ways in which a newborn loses body heat:
1.Evaporation.
2.Conduction.
3.Convection.
4.Radiation.

7. EVAPORATION
• When amniotic fluid evaporates from the skin. Evaporative losses
may be insensible (from skin and breathing) or sensible (sweating).
• Other factors that contribute to evaporative loss are the newborn’s
surface areas and air velocity. This is greatest source of heat loss at
birth.

8. CONDUCTION
• When the newborn is placed naked on a cooler surface, such as
table, scale, cold bed.
• The transfer of heat between two solid objects that are touching, is
influenced by the size of the surface area in contact and the
temperature between surfaces.

9. CONVECTION
• When the newborn is exposed to cool surrounding air or liquid is
affected by the newborn’s large surface area, air flow (drafts,
ventilation systems etc.), and temperature gradient.

10. RADIATION
• When the newborn is near cool objects, walls, tables, cabinets,
without actually being in contact with them.
• The transfer of heat between solid surfaces that are not touching.
Factors that affect change due to radiation are temperature gradient
between the two surfaces, surface area of the solid surfaces and
distance between solid surfaces.
• This is the greatest source of heat loss after birth.

11. MECHANISM OF HEAT PRODUCTION
• Metabolic process :
Source:
a) The brain, heart, and liver produce the most metabolic energy by
oxidative metabolism of glucose, fat and protein.
b) The amount of heat produced varies with activity, state, health status,
environment temperature.
• Voluntary muscle activity:
Sources:
a) Increased muscle activity during restless and crying generate heat.
b) Conservation of heat by assuming a flexed position to decrease exposed
surface area.

12. • Peripheral vasoconstriction:
Sources: In response to cooling, peripheral vasoconstriction reduces
blood flow to the skin and therefore decrease loss of heat from skin
surfaces.
• Non-shivering thermogenesis:
Sources: Heat is produced by metabolism of brown fat

13. • Thermal receptors transmit impulses to the hypothalamus, which
stimulate the sympathetic nervous system and causes norepinephrine
release in brown fat (found around the scapulae, kidney, adrenal
glands, head, neck, heart, great vessels, and axillary regions.
• Norepinephrine in brown fat activates lipase, which results in lipolysis
and fatty acid oxidation.
• This chemical process generates heat by releasing the energy
produced instead of storing it as Adenosine-5-Triphosphate

16. HYPOTEHRMIA
• Hypothermia occurs when the newborn’s axillary temperature drops
below the 36.5 degree centigrade.
• The following characteristics put newborns at a greater risk of heat
loss:
a) A large surface area-to-body mass ratio.
b) Decreased subcutaneous fat
c) Greater body water content.
d) Immature skin leading to increased evaporative water and heat
losses.
e) Poorly developed metabolic mechanism for responding to thermal
stress (e.g. no shivering)
f) Altered skin blood-flow (e.g. peripheral cyanosis)

17. Response to hypothermia
• Babies attempt to conserve heat by peripheral vasoconstriction→
increased anaerobic metabolism with acidosis → pulmonary
vasoconstriction → raised pulmonary arterial pressure → further
hypoxia with anaerobic metabolism → a vicious cycle.
• With continued hypothermia, usually when the temperature drops to
32°C, oxygen can not be released from the hemoglobin, resulting in
the blood having a bright red color, which should not be mistaken for
good perfusion.
• Free fatty acids released binds to albumin displacing bilirubin →
jaundice.

18. 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

19. Signs and Symptoms of Hypothermia in Infants

20. 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
Increased Respiratory Rate
• Pulmonary vasoconstriction occurs secondary to metabolic acidosis.
• Increasing Respiratory Distress related to decreased surfactant
production, hypoxia, & acidosis

21. 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

22. 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.

23. Metabolic Disturbances
• Metabolic acidosis
• Hypoxemia
• Hypoglycemia
• Progress due to continued metabolism of brown fat, release of fatty
acids and anaerobic metabolism (lactic acid)

24. Cold stress
• Infants lack shivering response
• Nonepinephrine (SNS) stimulates fat metabolism to produce internal
heat---blood---surface tissue
• Increased in metabolism---increased oxygen consumption
• Norepinephrine---vasoconstriction---decrease oxygen---decreased
glucose metabolism
• Result: hypoxia, metabolic acidosis, hypoglycemia

26. conclusion
• Attentiveness to temperature in a sick newborn is extremely
important
• Minimizing O2 consumption is the goal
• Recognition and treatment of infants with cold injury can be life
saving

27. Prevention of hypothermia

28. • Steps of warm chain
1. Warm delivery room
2. Warm resuscitation
3. Immediate drying
4. Skin to skin contact – kangaroo mother care.
5. Breastfeeding
6. Bathing postponed- during summer term babies can be sponged after first
24 hours. During winter, for the sick or LBW babies this can be postponed
by several days usually until the umbilical cord falls off, often by the end of
first week.
7. Appropriate clothing – dressing the baby in layers of warm light garments
gives better insulation than single layer of heavy clothing
8. Mother and baby together
9. Professional alertness
10. Warm transportation – weakest link in the warm chain.

29. Incubators ad radiant warmers
• Incubator – baby Is warmed by circulating warmed and humidified air
around the baby and the mechanism of heat transfer is by
convection.
• Radiant warmer – neonate lies on a waist high bed and heated from
above by a radiant source. Compared to incubator, infants under a
radiant warmer have more insensible water loss by evaporation which
can be reduced by using plastic sheets. It requires proper cleaning
and disinfection.

30. • Radiant warmers and incubators should be used in the servo control
mode with the abdominal skin temperature maintained at 36.2°C -37
°C depending on the birth weight of the neonate.
• Cheaper alternatives include – Oil- fin radiators – Warm air blowers –
Heaters – 200 watt electricity bulb
• These lack servo control mechanism
• Carry risk of hypo/ hyperthermia
Birth
weight in
kg
Set temp (°C)
<1.0 37.0
1.0-1.5 36.8
1.5-2.0 36.6
2.0-2.5 36.4
>2.5 36.2

31. Kangaroo Mother Care (KMC)
• Introduced in 1983 by Rey and Martinez in Colombia
– LBW infants nursed naked (wearing only cloth diaper) between mothers’
breasts
– Data from other countries show infants nursed by KMC have
• Fewer apnoeic episodes
• better blood oxygenation
• Lower infection rates
• Are alert longer and cry less
• Are breastfed longer and have better bonding
• Improved survival in low-resource settings

32. Components of KMC

34. hyperthermia
• Defined as a rectal / axillary temperature greater than 37.5°c (99.5°F)
• Predisposing factors are – Immature thermoregulatory center –
Decreased ability to produce sweat
• Common reasons for hyperthermia are – Over clothing –
Environmental exposure in summer – Poor feeding – Dehydration –
Direct sun exposure

35. Signs of Hyperthermia
• Tachypnea
• Tachycardia
• Flushing
• Hypotension
• Irritability
• Poor Feeding
• Skin Temp > Core Temp

36. Consequences of Hyperthermia
• Increased in Metabolic rate
• Decreased oxygen consumption
• Dehydration from increased insensible water loss
• Peripheral vasodilatation/ hypotension
• Fluid, electrolyte abnormalities
• Seizures

37. Treatment of Hyperthermia
• Cool quickly but safely (undress, un-bundle, decrease incubator
temperature), tepid water sponge bath
• Possible sepsis work up or acetaminophen

38. Thank you