Newborn Physiology Flashcards
Where are the most critical changes in a newborn?
Respiratory and cardiac system
What chemical events initiate breathing?
Mild asphyxia, hypoxia⇒ decreased PO2, pH, and increased CO2
Which 2 things prompt fetal circulatory structures to begin closing?
First breath plus cutting umbilical cord
When does surfactant production begin?
Around 24-25 weeks
When does surfactant production peak?
34-36 weeks
What is surfactant made up of?
Lecithin & sphingomyelin in a 2:1 ratio (ideally)
Respiratory rate of a newborn
60-70, up to 100
Will decrease to 30-60
Signs of respiratory distress in newborns
Grunting, flaring, retracting, tachyphea, cyanosis, pallor, poor muscle tone, apnea
Which circulatory structures close on the fetus to transition into adult circulation?
Foramenovale, ductus arteriosus, ductus venous
Are crackles a normal finding when listeningto a newborn’s lungs?
Yes, for the first few hours, infants have a lot of mucus innings
When does the foramen ovale close?ductus arteriosus?ductus venosus?
Foramen ovale: Closes functionally 1-2 hours after birth (permanently after 2-4 months)
Ductus arteriosus: closes functionally 10-15 hours after birth (permanently in 1-2 weeks)
Ductus venosus: closes functionally soon after birth (permanently at 1-2 weeks)
Where are the pressure changes when the transition from fetal to neonatal circulation occurs?
Heart / pulmonary & systemic circulation
When should an infant’s cardiovascular assessment be performed?
When the infant is asleep/quiet
What is an infant’s heart rate normally?
110-160
What is a passing oximetry screen for an infant?
≥ 95% 02 sat in right hand or foot
≤ 3% difference between right hand and foot
What is a failing oximetry test for an infant?
<90% in initial/repeat screening either foot or right hand
90-94% in right hand and foot on 3 measures 1 hour apart
> 3% difference in 02 sat by right hand and either foot on 3 measures, 1 hour apart
Where is pre ductal blood?
Right hand/arm
Where is post ductal blood?
Lower extremities
Normal temperature for a newborn?
Axillary= 36.5-37.5°C (97.7-99.5°F)
Why are transient murmurs not uncommon in infants?
Not all of the ducts in the heart are fully closed yet
How does an infant produce heat?
Nonshivering thermogenesis, increase in muscle activity/restlessness, peripheral vascular constriction
Why is the breakdown of brown fat not ideal?
Consumes a lot of calories and oxygen
What are the 4 methods of heat loss?
Conduction, convection, evaporation, radiation
What is conduction?
Contact with cold objects
What is convection?
Cold air draft
What is evaporation?
Wet/moist skin dried by air resulting in cooling
What is radiation?
No direct contact, transfer of heat to a cooler object
What hormone is released to metabolize brown fat?
Norepinephrine
How long do iron stores last?
4-6 months
When does intestinal flora emerge in a newborn?
After 1st feeding
What is the normal blood glucose range for an infant after 24 hours?
45-96 mg/dl
When is vitamin K administered to infants? What does vitamin K do?
Administered within the 1st hour of life and it influences the activation of coagulation factors
what is considered hypoglycemic for infants after 24 hours?
<40mg/dl
What kind of cry does a hypoglycemic baby have?
Weak, high pitched
What is seen in an infant with hyperbilirubinemia?
High levels of unconjugated bilrubin
What causes jaundice?
Unconjugated bilirubin
What is bilirubin?
Breakdown product of hemoglobin
How is bilirubin transported and excreted?
Binds to albumin, transported to the liver and bound to intracellular proteins and conjugated ⇒ excreted in bile and carried to intestines ⇒ further broken down in intestine
What is unconjugated bilirubin?
Indirect, lipid soluble, non-excretable. Crosses the blood brain barrier
What is conjugated bilirubin?
Direct, water-soluble, excitable
What kind of jaundice do most infants have 48-72 hours after birth?
Physiologic
How long does physiologic jaundice typically last?
> 1 week in term infants, 2 weeks in premature infants
When does pathologic jaundice occur?
Within 24 hours of birth
What may cause pathologic jaundice?
Rh/ABO incompatibility, sequestered blood, breastfeeding or delayed feedings
What does a positive directCoombs test on newborn blood indicate?
Hemolytic disease
What does a positive indirect Coombs test on maternal blood indicate?
Anti- Rh antibodies
What is the goal of jaundice treatment?
Kernicterus prevention
What is phototherapy?
Rapid conversion of bilirubin to photobilrubin which does not require conjugation in the liver
What can acute bilirubin encephalopathy lead to?
Kernicterus
What % of term infants get jaundice? Preterm?
60%, 80%
5 common screenings done on all newborns
Critical congenital heart disease, hyperbilirubinemia screening, glucose homeostasis screening, genetic disease screen, hearing screen
Why are neonates prone to infection?
Their defense mechanisms are not fully mature
What are some portals for bacterial entry on neonates?
Eyes, skin breakdown, and cord stump
Which antibody is passed across the placenta passively during the last trimester of pregnancy?
IgG
Which antibody is passed in the colostrum and is produced by newborns at 1 month?
IgA
Which antibody is produced by the fetus in response to infection and does not cross the placenta?
IgM
3 categories of neonatal infections
Acute life- threatening infection of the blood, localized infections, congenital infections
What is considered vertical transmission?
Mother to infant: transplacental, ascending, intrapartum
What is horizontal transmission?
From nursery personnel and hospital environment
Signs of sepsis
Temp instability/hypothermia, respiratory distress, poor feeding/feeding intolerance, lethargy/irritability, persistent hypoglycemia
Why can newborns dehydrate quickly?
Kidneys are immature
Why does “brick-dust” urine occur?
Uric acid crystals in urine
What does the Ballard maturational tool assess? What are the components of this assessment
Determines gestational age. 6 neuromuscular maturity assessments, 6 physical maturity assessments
5 behavioral capacities of a newborn?
Habituation, orientation, self-quieting, motor maturity, social behaviors
Where can newborns see the clearest?
8-12 inches from them, and they like to see bright colors
Can newborns recognize voices?
Yes, especially maternal voice
What smell do newborns respond to?
Breast milk
What kind of taste does a newborn prefer?
Sweet tastes
How often does an infant cry per day? When will the crying peak?
5 minutes to 2 hours per day. peaks at 2 months, then decreases
What is another term for shaken baby syndrome? When does this most often occur?
Abusive head trauma. Most common at 2-4 months
Who accounts for the majority of perpetrators for causing shaken baby syndrome?
Biological fathers ⇒ stepfathers ⇒ mothers’ boyfriend ⇒ mothers
