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
