4. 4
Thermoregulation is the ability to maintain a
balance between heat production and heat loss in
order to maintain body temperature within a
certain normal range.
According to the World Health Organization(WHO,
1997;2003) andAmerican Academy of Pediatrics (AAP,
2017) a newborn is normothermic when its body
temperature is between 36.5属C and 37.5属C.
The Acute Care of at-Risk Newborns Neonatal
Society (ACoRN) define normal axillary
temperature to be between 36.3属C and 37.2属C
(ACoRN, 2012).
Hypothermia is defined as follows:
Mild : Core temperature between 36 36.4C
Moderate : Core temperature between 32
35.9C
Severe : Core temperature between < 32C
For every decrease of 1属C , there is 28% increase in
mortality (Laptook etal, 2007)
6. 2
Neonatal hypothermia has potentially life threatening effects
including cardiopulmonary, central nervous system, vascular
system and metabolic disturbances, which may lead to increased
morbidity and length of stay.
Among the causes that contributes to hypothermia in newborns
include poor thermoregulatory control during resuscitation,
environment and transportation prior to admission to NICU.
Risk factors of hypothermia include prematurity, low birth weight
and intrauterinegrowth restriction. Other risk factors include
abnormal skin integrity including gastroschisis, exomphalos and
neural tube defects and neonates with neurological impairment.
7. Admission Hypothermia among VLBW infants in
Malaysian NICU
Nem-Yun Boo et al, 2013, Journal of Tropical
Pediatrics
Retrospective analysis of prospectively
collected data from MNNR of 32 Malaysian
government NICU
Results:
Median temperature was 36属C
64.8% of them were hypothermic on admission
Hypothermic infants had significantly lower
birth weight and gestational age
A significant higher proportion of
hypothermic infants developed RDS and/or
IVH, died within 12h of admission and died
before discharge
Although not statistically significant, data
suggest that NICUs practicing more preventive
measures had lower rates of admission
hypothermia
7
8. Reducing IVH following implementation of a prevention
bundle for neonatal hypothermia
8
Chiu et al., 2022, Journal Prone
Quality improvement project, done in Taiwan
Two time periods: Pre-intervention and post-
intervention
3 leading causes to hypothermia found;
Low delivery room temperature
Inconsistent practices by various neonatal
staff
Uncertainty of correct practice by medical
staff
10. Typically a wet newborn with a high surface
area to volume ratio moves from a warm
aqueous uterine environment into a cooler,
dry delivery room.
The newborn immediately loses heat by
evaporation, convection, conduction and
radiation, dependent on the ambient air
pressure, temperature and humidity and the
temperature of surrounding surfaces.
As the temperature falls between 36属C to 35属C,
newborn infants peripherally vasoconstrict and
initiate non-shivering thermogenesis (NST) of
brown adipose tissue.
11. Brown fat constitutes approximately 1.4 percent of the
body mass of newborns greater than 2 kilograms in
weight and is prominent in nuchal subcutaneous tissue,
around the kidneys, the mediastinium and intra-
scapular regions.
Brown fat contains high levels of triglycerides, is rich in
capillaries and is innervated by sympathetic nerve fibres
Brown adipose tissue can be identified after 26 weeks
gestation.
Post delivery brown adipose tissue does not continue to
develop, as it would have done in the intra- uterine
environment, so preterm neonates remain at a
disadvantage.
The preterm infant has the additional disadvantages of
decreased fat for insulation, decreased glycogen stores,
immature skin which increases water loss, poor vascular
control, a lower maximal metabolism and a narrower
range of thermal control
12. NST is triggered by a surge in catecholamines,
released from the sympathetic nervous system
during times of cold stress.
Noradrenaline combines with beta 3
adrenoreceptors on brown adipocytes and activates
adenylate cyclase which increases cytosolic cyclic
adenosine monophosphate, phosphorylates protein
kinase, and activates hormone-sensitive lipase.
Uncoupling of oxidative phosphorylation by the
protein thermogenin results in marked heat
production and a significant increase in metabolic
rate
With continued cold stress the stores of brown fat
become depleted resulting in hypoxia and
hypoglycaemia.
14. Clinical
signs
of cold
stress
During development of hypothermia,
a neonate may become cold to the
touch, restless, irritable or lethargic,
hypotonic, a poor feeder with gastric
distension or increased aspirates, and
bradycardic.
As the condition worsens the neonate
can become tachypnoeic or apnoeic,
hypoglycaemic, hypoxic and
metabolically acidotic, develop
coagulation defects, acute renal
failure and necrotizing enterocolitis
15. Hyperthermia
Neonatal hyperthermia is defined as a body
temperature above 37.5 属C.
Clinical signsof hyperthermia
Hyperthermia is usually secondary to overheating due to an
external source; however it can be secondary to other
factors including sepsis, hypermetabolism, neonatal
abstinence syndrome, and maternal hyperthermia at
delivery.
Clinically hyperthermia may present with irritability, poor
feeding, flushing, hypotension, tachypnoea or apnoea,
lethargy and abnormal posturing, in addition to an elevated
peripheral or core temperature. If untreated then seizures,
coma, neurological damage and ultimately death may occur
18. Preventative measures temperature control
at resuscitation
Traditional techniques for decreasing heat loss include the
provision of a warm delivery room.
The immediate drying of the infant under radiant heat,
discarding the wet towel and replacing it with a warm
towel, in a warm draught-free area is recommended.
However very low birthweight (<1500 g) preterm babies
are likely to become hypothermic despite all these
measures. As a consequence, recommendations to place
newborns inside plastic wrapping or bags with their heads
protruding, have been developed.
The Heat Loss Prevention (HeLP) randomised controlled
trial found that polyethylene occlusive skin wrapping
prevented heat loss at the delivery of infants less than 28
weeks gestational age. Resuscitation should continue
unhindered by the heat loss preventative measures.
Thermoregulation In NICU
The mainstay of care is to maintain the newborn in
a neutral thermal environment which ensures
minimal metabolic activity and oxygen
consumption are required to conserve body
temperature.
Incubators are now specifically designed to
minimise losses by radiation, convection,
conduction and evaporation whilst allowing clear
visibility and access to the patient.
A skin temperature probe is placed away from
regions where brown fat metabolism occurs and
should be reflective if under a radiant warmer.
Re-warming after a period of hypothermia should
be a well controlled, closely observed treatment,
monitoring for hypoxaemia and metabolic acidosis,
cardiovascular instability, hydration status,
hypoglycaemia and hyperbilirubinaemia.
Rapid rewarming has been advocated but may be
associated with vasodilatation and seizures
19. The 10 Step Warm Chain for thermal care. Adapted from WHO 1997
20. Conclusion
Neonatal hypothermia is a potentially life threatening condition that leads increment in
morbidity and mortality.
Effective thermoregulation and prompt corrective thermoregulatory measures are
essential during neonatal resuscitation to reduce incidence of hypothermia in newborn.
Clear and concise thermoregulatory guideline should be incorporated into the existing
standard neonatal resuscitation guideline.
Continuous training should be conducted among medical staff with emphasis of strict
adherence to thermoregulation during resuscitation.
21. References
Laptook AR, Salhab W, Bhaskar B; Neonatal Research Network. Admission temperature of low birth weight
infants: predictors and associated morbidities. Pediatrics. 2007;119(3).
www.pediatrics.org/cgi/content/full/119/3/e643
Nem-Yun Boo, Irene Guat-Sim Cheah, for Malaysian National Neonatal Registry, Admission Hypothermia
among VLBW Infants in Malaysian NICUs, Journal of Tropical, Pediatrics, Volume 59, Issue 6, December 2013,
Pages 447452, https://doi.org/10.1093/tropej/fmt051
Chiu W-T, Lu Y-H, Chen Y-T, Tan YL, Lin Y-C, Chen Y-L, et al. (2022) Reducing intraventricular hemorrhage
following the implementation of a prevention bundle for neonatal hypothermia
https://doi.org/10.1371/journal.pone.0273946
NHS Clinical Guideline : Thermoregulation (2020)
https://www.eoeneonatalpccsicnetwork.nhs.uk/wp-content/uploads/2021/10/Thermoregulation-
guideline-2020-Final.pdf
Sarah Waldron, Ralph MacKinnon. Neonatal Thermoregulation (2007)
https://www.infantjournal.co.uk/pdf/inf_015_nor.pdf
