Chapter 19: Normal Newborn: Processes Of Adaptation Flashcards
What is the purpose of fetal lung fluid?
- The aveoli produce fetal lung fluid that expands the alveoli and is essential for normal development of the lungs.
- Some of the fluid empties from the lungs into the amniotic fluid.
In preparation for birth, what happens to fetal lung fluid?
-Production of lung fluid decreases in preparation for birth. (Fluid must be cleared for the infant to breathe air)
When does absorption of fetal lung fluid begin?
During early labor.
By the time of birth, only about 35% of the original amount remains.
Absorption of fetal lung fluid is accelerated by
Secretion of fetal epinephrine and corticosteroids.
Absorption of fetal lung fluid may be delayed by
- Cesarean birth without labor.
- C/S baby may be born with more fluid still in lungs (need to get fluid out)
The removal of fetal lung fluid reduces
pulmonary resistance to blood flow that is present before birth and enhances the advent of air breathing.
Surfactant is detectable by what weeks of gestation?
24-25 weeks of gestation. *
By what weeks is there a sufficient amount of surfactant produced to prevent respiratory distress syndrome?
By 34 to 36 weeks. *
Accelerated fetal lung maturation occurs in
- A fetus who has intrauterine growth restriction.
- A fetus who is stressed by conditions such as chronic maternal HTN, preeclampsia, and prolonged rupture of membranes (PROM).
Slow fetal lung maturation occurs in
Infants of mothers with diabetes.
Infant breathing is initiated by what 3 factors?
- Mechanical factors
- Chemical factors
- Thermal factors
Why is surfactant important in infants as they begin to breathe at birth?
- Surfactant lines the inside of the alveoli and reduces surface tension within alveoli, allowing the alveoli to remain partially open when the infant begins to breathe at birth.
- Without surfactant the alveoli collapse as the infant exhales.
Absorption of Fetal Lung Fluid
- During labor, the fluid begins to move into the interstitial spaces, where it is absorbed.
- At birth the infant’s first breath must force remaining fetal lung fluid out of the alveoli and into the interstitial spaces around the alveoli to allow air to enter the lungs.
Mechanical Factors
- During a vaginal birth, the fetal chest is compressed by the narrow birth canal.
- The fluid passes out of the mouth or nose or is suctioned as the head emerges from the vagina
- When the pressure against the chest is released at birth, recoil of the chest draws a small amount of air into the lungs and helps remove some of the viscous fluid in the airways
- This reduces the amount of negative pressure needed for the first breath after birth
Approximately how much fetal lung fluid is forced out of the lungs into the upper air passages during birth?
1/3 *
The first breath of a baby is referred to as the
Inspiratory gasp
Chemical Factors
- Inspiratory gasp is triggered by an increase in PCO2 and decrease in pH and PO2 levels.
- This triggers the aortic and carotid chemoreceptors to stimulate the respiratory center in the medulla.
- A forceful contraction of the diaphragm results, causing air to enter the lungs.
Chemical Factors: Stimulation of the respiratory center and breathing do NOT occur if
Prolonged hypoxia causes CNS depression.
Thermal Factors
- After birth, infant moves from warm, fluid-filled uterus into an environment where the temperature may be much cooler.
- The cold stimulates the skin nerve endings, sending impulses to the brain that stimulate the respiratory center and breathing.
- The newborn begins to respond with a rhythmic respiration.
Excessive cooling of the infant can lead to
Cold stress.
Hazards of Cold Stress include
- Increased oxygen need (d/t increased metabolic rate and metabolism of brown fat)
- Decreases surfactant production
- Respiratory distress (d/t increase oxygen need)
- Hypoglycemia (d/t metabolism of glucose to produce heat)
- Metabolic acidosis
- Jaundice (d/t increased fatty acids)
How much air remains in the lungs after the first breaths are drawn?
20-30 ml
How can crying help with absorption of fetal lung fluid?
- Crying increases the pressure within the lungs.
- This leads to absorption of fetal lung fluid into interstitial spaces and absorption into pulmonary and lymphatic systems.
How long does it take for complete absorption of fetal lung fluid to occur?
- Takes several hours.
- Some lungs sound moist when first auscultated but become clear in a short time.
How much can an infant’s temperature drop if not kept warm at birth?
Can drop 0.2 degrees to 1 degree C (0.5 to 1.7 degrees F) per minute. *
What are newborn characteristics that can lead to heat loss?
- Skin is thin and blood vessels are close to the surface.
- Little SQ or white fat is present
- Heat is readily transferred from the warmer internal areas of body to cooler surfaces and surrounding air
- Newborns lose heat at a rate 4x greater than that of adults.
Why do healthy full term infants remain in a position of flexion?
-This decreases the amount of skin surface exposed to surrounding temperature and decreases heat loss.
Why are premature infants not able to maintain flexion?
They have decreased muscle tone to remain flexion.
What are the methods of heat loss in an infant?
- Evaporation
- Conduction
- Convection
- Radiation
Evaporation
Occurs when wet surfaces are exposed to air.
As the surface dries, heat is lost.
How do infants lose heat through evaporation?
- At birth, when amniotic fluid on the skin evaporates.
- During bathing.
- Insensible water loss from the skin and respiratory tract increases heat loss from evaporation.
How can you prevent heat loss through evaporation in an infant?
Drying the infant, especially the head, as quickly as possible after birth and after bathing helps prevent heat loss by evaporation.
Conduction
Movement of heat away from the body occurs when newborns have direct contact with objects that are cooler than their skin.
How can infants lose heat through conduction?
- Placing infants on cold surfaces or touching them with cool objects.
- The reverse is also true, contact with warm objects increases body heat by conduction.
How can you prevent conductive heat loss in an infant?
- Warming objects that will touch the infant.
- Placing the unclothed infant against the mother’s skin (“skin to skin”).
Convection
Convection occurs when heat is transferred to air surrounding the infant.
What can cause heat loss in an infant through convection?
Air currents from air conditioning or the movement of people.
How can you prevent heat loss through convection in an infant?
- Keeping the newborn away from drafts
- Maintaining warm environmental temperatures (i.e incubator)
- Warming oxygen before prolonged administration
Radiation
The transfer of heat to cooler objects that are not in direct contact with the infant.
How can an infant lose heat through radiation?
- Placed near cold windows.
- Placed in an incubator with cold walls (infant is cooled despite the warm temperature inside of the incubator)
How can you prevent heat loss from radiation in an infant?
- Incubators with double walls
- Placing cribs and incubators away from windows and outside walls.
- Use radiant warmer to transfer heat from the warmer to the cooler infant.
Shivering in a newborn
- Newborns rarely shiver except during prolonged exposure to low temperatures.
- Shivering is not an important method of thermogenesis in a newborn.
When infants are cold, instead of shivering, what do they do?
-They cry and become restless*
(This increased activity and flexion help generate some warmth and reduce the loss of heat from exposed surface areas of the body)
Why are premature infants at an increased risk for cold stress?
- Have decreased muscle tone and are unable to maintain a flexed position.
- Have thinner skin and even less white SQ fat than full-term infants
In infants, exposure to cool temperature can cause
Vasoconstriction, preventing heat loss from the skin and causes the skin to feel cool to the touch.
Acrocyanosis
- Bluish discoloration of the hands and feet.
- Occurs when infant is exposed to cool temperatures and peripheral vasoconstriction occurs.
How can a drop in temperature affect metabolic rate and respiratory functions?
A drop in temperature increases the metabolic rate as much as 100%, causing above-normal oxygen and glucose use.
What is the primary method of heat production in infants?
Nonshivering Thermogenesis
Nonshivering Thermogenesis
The metabolism of brown fat to produce heat.
What causes the brown color of brown fat?
It’s abundant supply of blood vessels.
Where is brown fat primarily located?
- Back of the neck
- In the axillae
- Around the kidneys
- Adrenals
- Sternum
- Between the scapulae
- Along the abdominal aorta
Metabolism of Brown Fat
-Generates more heat than white SQ fat
Blood passing through brown fat
is warmed and carries heat to the rest of the body.
When does nonshivering thermogenesis begin?
begins when thermal receptors in the skin detect a skin temperature of 35° to 36° C (95° to 96.8° F) *
What happens during nonshivering thermogenesis?
- Thermal receptor stimulation is transmitted to the hypothalamus thermal center.
- As a result, NE is released in brown fat, initiating its metabolism.
NST goes into effect even before
A change occurs in skin temperature or in core body temperature.
(Therefore, NST may begin in an infant when skin temperature has been cooled, even though the core and skin temperature measurements show normal readings)
Activating thermogenesis before core temperature decreases allows
The body to maintain an internal heat at an even level.
A decreased core temperature will not occur until
NST is no longer effect
What infants are likely to have inadequate brown fat stores?
- Preterm infants
- Infants with intrauterine growth restriction (may deplete brown fat stores before birth)
- Infants with hypoxia,hypoglycemia and acidosis