1.2 - Thermoregulation In The Newborn Flashcards
what is the intrauterine temperature
37.8C
What is the ideal temperature when a neonate is born
26
What are the two key factors that the newborn has difficulty maintain body heat
- newborn ratio of body mass to body surface. body surface is much smaller, therefore higher body surface area to body mass ratio in the newborn
- Term babies have a limited ability to maintain their temperature by shivering or muscle movement
What is thermoregulation
thermoregulation is the process by which the body balances heat production when there is heat loss to maintain the correct body temperature - homeostasis
Keeping babies warm
vitally important to reduce the effects of thermal stress in the challenged neonate and maintain a neutral thermal environment
What are the methods of Heat Loss in a Neonate
- Evaporation - heat loss through wet skin ie amniotic fluid
- Convection- heat loss from cooler air circulating around warmer skin, particularly when exposed (cold draft or air conditioning)
- Conduction- heat loss through direct contact with a cold surface (eg. Scales)
- Radiation- heat loss from heat radiating towards a cooler surface (eg. A cold wall)
What is the Thermoneutral Range of Temperature
The narrow range of environmental temperature at which the basal metabolic rate of the baby is at a minimum, oxygen consumption is at lowest and baby maintains its normal body temperature
(Essentially this means the baby is able to use the least energy possible to keep itself warm and is relaxed)
Why should a baby be kept in the thermoneutral range of temperature?
This is so that their energy is utilised for growth and other vital functions
Physiological Processes behind Neonatal Thermoregulation
- the heat-regulating mechanism in the neonate is inefficient and the body temperature may drop
- should be born into a temperature of 26 degrees, dried and wrapped up, ideally with skin-to-skin
- the baby is used to an intra-uterine temperature of 37.8 degrees
- wet skin at birth and high surface area-to volume ratio means that heat is lost through the skin surface
- the baby has a lack of subcutaneous fat at term;
- and a lack of adipose tissue & brown fat as a preterm baby -poor energy stores and limited brown fat means there is limited thermogenesis (heat production)
What is thermoregulation
- The control of the generation and loss of heat activated and performed through thermal sensors,
- afferent pathways, an integration system in the CNS, efferent pathways and target organs
- in the first few days, neonates sweat only from their head region
- the area where heat can be lost (the head) is very small compared to the body mass that can generate heat
- neonates are unable to shiver
- if they become cold, they can decrease their surface area by adopting the fetal position
Describe non-shivering thermogenesis
- Heat is generated through metabolism in the brown adipose tissue
- brown adipose tissue is situated around the kidneys, mediastinum, around the nape of the neck and scapula, along the spinal column and around the large blood vessels in the neck
- it is for this reason that it is crucial to keep the nape of the neck warm in neonates in order to maximise heat regulation
- brown adipocytes (fat cells) begin to proliferate at 26-30 weeks gestation.
- These have an extremely high propensity for metabolic activity and therefore heat production
- adrenaline and thyroxine increase the metabolic activity within the brown fat cells and heat is produced
What is Cold Stress?
A cascade of physiological events caused by the infant’s use of chemically mediated thermogensises or non shivering thermogenesis in an attempt to increase the core temperature as their primary source of heat production
- This is when the peripheries are cold and the trunk of the body is warm
Cold Stress causes what change in hormones in order to heat up the neonate?
- The activity of the sympathetic nerve fibres during cold stress causes the adrenal glands to release the necessary catecholamines, such as noradrenaline
- this stimulates the anterior pituitary gland
- releases thyroid-stimulating hormone (TSH)
- causes the thyroid gland to increase its production of thyroxine (T4)
- Adrenaline and thyroxine increase the metabolic activity within the brown fat cells
- and heat is produced but this process requires extra oxygen and glucose
Heat Gain Methods in a Neonate
- metabolic processes such as oxidative
- metabolism of glucose, fats and proteins
- physical activity such as crying, restlessness and hyperactivity
- non-shivering thermogenesis generated through metabolism in brown adipose tissue
Heat Loss Methods in a Neonate
Evaporation Convection Radiation Conduction
newborn temperature
- 36.5 and 37.5
- below 36.5 hypothermia
heat loss in the neonate
- respiratory disorders
- severe conditions - metabolic
- hypoglycaemia leads to convulsions
- need more o2
The Warm Chain
- warm delivery room - 25 degrees or above
- immediate drying - warm dry towel
- skin to skin contact - dried again with a warm dry towel, hat
- breastfeeding - asap post birth within the first hour - calories to help maintain a normal body temp
- bathing and weighing postpone - 2 hours after birth
- appropriate clothing - tight swaddling reduces baby movement
- mother and baby together
- warm transportation
- warm resuscitation
- training of health care providers
skin to skin ie Kangaroo care
- direct skin to skin contact with the mother
- reduces infection
- promotes breastfeeding
- thermoregulation
- maternal infant bonding
- improves survival
- better outcomes
*
selection criteria for s2s
- birth weight >600 grams >30 weeks ga
- ventilator for at least 24 hour before first skin to skin
- SIMV <35 breaths per minute fi02 <.50 50%
- stable vitals
- stable blood gases
- no signs/symptom of sepsis
- not receiving any vasopressors (no chest tube)
- lines well secured
what areas of the neonate would you find brown adipose tissue
- inter-scapula
- Medisturem
- kidneys
- liver
key information
pre term infants are at risk of hypothermia due to:
- decreased fat isolation
- decreased fat
- large surface area
- weight ratio
- increased o2 consumption
- immature thermal regulatory ability
- increase transepidermal water loss
- poor ability to change posture
brown adipose tissue has the following features
- present from 25 weeks
- inadequate at 32 weeks to produce enough heat by non shivering thermogenesis
what factors may impair the neonates responses to process thermoregulatory information
- severe illness
- lack of brown fat stores
what is the fetal inter temptation compared to maternal temperature
- 37.8 inuterine
- increased by .03.05 degrees
Explain the relationship between physiology maturity and thermal stability
Describe challenges of thermoregulation in the special care environment
Describe how you can facilitate thermoregulations for the challenged infant - the warm chain
- warm delivery room - 25 degrees or above
- immediate drying - warm dry towel
- skin to skin contact - dried again with a warm dry towel, hat
- breastfeeding - asap post birth within the first hour - calories to help maintain a normal body temp
- bathing and weighing postpone - 2 hours after birth
- appropriate clothing - tight swaddling reduces baby movement
- mother and baby together
- warm transportation
- warm resuscitation
Heat loss - via convection, radiation, Evaporation, conduction
Non-shivering Thermogenesis
Hypothalamus > increased sympathetic activity
two different ways
Releases of norepinephrine in BAT>Activates 5’- monodeiodinase> stimulates UCP1
TSH release>stimulates release of T4>T4 converts to T3
Stimulates UCP1 >transport of protons in mitochondria > fat is oxidized>Heat is produced
infant hypothermia may lead to
Hypoxemia
Acidosis
Hypoglycemia
decreased growth
Mentimeter
Mentimeter
A premature infant’s thin skin and
surface area to body mass ratio allows for increased heat loss
Large
Term infants can reduce surface area by
Flexing their extremities onto their trunk
Nonshivering thermogenesis, is initiated in the
Hypothalamus
The key enzyme which regulates non shivering thermogenesis is
uncoupling protein 1
A neutral thermal environment is one where
temp range at which heat production is at the minimum needed
incubators are specifically designed to minimise heat losses by
Radiation
convection
conduction
evaporation
Case Study
Potential problems/complications
- Low birth weight - risk of losing further weight
- Hypothermia
- Hypoglycaemia
- risk of iv therapy/cannualation
- rising HR AND RR
- RDS
- Separation from mum ?
- reduced BF supply
- Sepsis
Goals of care/planning including neurodevelopment outcomes
- BGL’s (preterm)
- Thermoregulation
- nutritional needs
- S2S with Mon & dad
- neuroprotective care
- low stress environment
Interventions including rationale-neonatal and maternal family
- s2s with father
- under heater
- regular monitoring
