Hypothermia - What temperature causes brain damage in babies ?

Hypothermia can happen still in term babies but they do have several protective factors, one is they develop brown fat in the last few weeks of gestation this brown fat and burns in order to produce heat in their body after the birth.

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Hypothermia in Infants

Some methods of heat production are peripheral days of constriction increased muscle flexion and activity and brown fat metabolism.

When you and beans get cold one of the bodies first mechanisms to generate heat is to constrict the blood vessels and the arms and legs. This helps to keep blood in the core of the body and prevents heat loss from the skin surface. Although this helps to conserve heat prolonged periods of peripheral vasoconstriction reduce the amount of oxygen available to the tissue.

In the adult, heat is produced through shivering that infants have a poor ability to shiver, rather than shivering infants increase activity through flexion and movement which generates muscular warmth. They also have protection of more subcutaneous fat this helps to insulate them from the cold around them.

Term babies also are still prone to hypothermia because they can't shiver no neonate is capable of shivering. Term babies can become hypothermic if they're exposed to too much cold or if they're sick. When they're sick the brain does not work properly to regulate the body's heat. so if a term baby is become hypothermic without any apparent cause check first for sepsis.

When a baby is septic often their temperature is low instead of high. other ways that term babies can become hypothermic are through problems with their brains such as asphyxia or meningitis. When the baby is severely septic the temperature can fluctuate up and down. Another problem that can happen is exposure through resuscitation or through emergency transport or phototherapy all of these can be dangerous for term babies.

Flexion also helps to decrease the body surface area, premature and sick infants may be unable to flex in response to cold stimuli the way that mature infants can the premature and then has poor muscle tone and primarily lives with his extremities extended. The premature infant has a very large surface area to body mass ratio, in other words, the large area is exposed to the environment this can this can result in rapid heat loss.

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The third mechanism of heat production is brown fat metabolism this process is initiated in the hypothalamus, by the way, the sympathetic nervous system. Brown fat is located around the kidneys adrenal glands the mediastinum subscapular and axillary areas and is very limited and premature infants.

Storage of brown fat occurs primarily during the third trimester of pregnancy. The more premature the infant the less brown fat is stored, your intranet friend is released at the brown fat site as a result of cold stress, when norepinephrine is released free it causes the release of free fatty acids.

One consequence due to the release of free fatty acids is that it will compete with Billy ribbon for albumin binding sites. This increases the risk of hyperbilirubinemia and possible conductors of the three methods of heat production brown fat metabolism is the one most utilized by the new one.

The methods of heat loss are conduction, convection, evaporation and radiation. Conduction is the transfer of heat between two solid objects that are in direct contact an example of this would be between the skin of an infant and a cooler object such as the caregiver's hand or a temperature probe.

Convection is the transfer of heat between a solid surface such as the infant in either moving air or liquid around the infant. Evaporation is a loss of heat through the energy used in the conversion of water to its gaseous state and radiation is the transfer of heat between a solid surface.

That are not in direct contact an example of this would be between the isolette and the outside one. Cold stress in the term newborn includes pulmonary vasoconstriction. when the term newborn becomes old a sequence of physiologic responses begins to occur.

When cold stress is detected by the body's peripheral in core temperature sensors signals are sent to the hypothalamus. This activates the release of norepinephrine in response norepinephrine causes pulmonary vasoconstriction, this leads to a greater possibility of right to left shunting which leads to hypoxemia.

Norepinephrine also causes peripheral vasoconstriction when prolonged and coupled with increased oxygen consumption this leads to hypoxia. An increased metabolic rate can lead to increased oxygen consumption and increased glucose.

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The preterm newborn is at much greater risk for developing hypothermia forming reason. These reasons include a larger surface area to body mass ratio decreased amounts of insulating fat, premature infants have thinner and immature skin with the blood vessels near the surface they have poor muscle tone, little to no brown fat and also due to the amniotic fluid, fluid loss, equals evaporative heat loss in the return.

When the infant is cold stressed the metabolic rate increases to produce heat if the infant's metabolic rate is increased glycogen stores and blood glucose are used at much faster. This predisposes the infant to hypoglycemia episodes to remember the body's needs glucose to meet its energy need.

When the infant is cold stress wrong fat is converted to heat and free fatty acids the fatty acids in lactic acid are formed during muscular activity by the breakdown of glycogen. They are then dumped into the bloodstream causing a lower blood PH and metabolic acidosis. Acidosis also causes vasoconstriction of the pulmonary blood vessels resulting in low blood oxygen levels.

Extra oxygen is needed when the infant is cold in order to produce heat, a cold infant with normal lungs will increase his respiratory rate in order to get extra oxygen. If the infant has diseased lungs you may not be able to get enough oxygen to maintain brain and body functions.

Infants may show signs of respiratory distress such as grunting retracting nasal flaring and tachypnea. An infant does not have to be severely cold stressed to develop these consequences, some infants demonstrate these consequences even if their temperature drops only one to two degrees. Cold stress results in the release of norepinephrine leading to vasoconstriction, this reduces heat loss and initiates heat production.

Increasing metabolic rates caused an increase in utilization of glucose stores, the infant uses anaerobic metabolism to produce heat resulting in lactic acid production and hypoxia. The end results are metabolic acidosis hypoglycemia and death and fibre permeate contains. 

The Efficiencies in Preterm Babies

Their brains are immature and they just can't regulate the body's heat the way it turns baby does. also, they have less subcutaneous fat to insulate them from the cold around them. they also don't have brown fat to burn.

The baby's surface area is large for their weight so they radiate more heat into the air around them. Their lungs are immature and they need oxygen in order to produce heat. also premature babies often cannot digest calories well so therefore they can't take in enough calories to burn to keep warm. Their heads are also very large for their size so lots of the heat radiates right out of their heads so it's very important to keep hats on premature babies or all babies if it's cold.

So they have none of the protective qualities that a term baby has they have no reserve they can die very quickly and often there were no outward signs.We didn't even know that they were hypothermic yet that death was totally preventable.

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