Newborn Transition Flashcards
What are the structures of the upper respiratory tract?
1) nose
2) nasal cavity
3) sinuses
4) larynx
5) trachea
What are the structures of the lower respiratory tract?
1) lungs
2) bronchi and bronchioles
3) alveoli
Fetal pulmonary circulation has (high/low) vascular resistance
high
lungs are closed, fluid-filled w/ minimal blood flow
What occurs during the canalicular stage?
@16-24wks GA
- terminal alveolar sacs appear
What occurs during the saccular stage?
@28-34wks GA
- capillaries come into contact with alveolar basement membrane
- primitive alveoli develop and are lined w/ 2 types of alveoli cells
1) type 1 = thin epithelial alveolar cells = gas exchange
2) type 2 = cuboidal epithelial cells = surfactant production and storage
What occurs during the alveolar period?
@36wks GA through childhood
- more alveoli form –> larger surface area for gas exchange
- 1/3 of alveoli mature at birth; rest mature after
What happens to the fluid in fetal lungs?
begins to clear a few days before labor
Fetal Hgb has (higher/lower) affinity for O2.
higher
- facilitates O2 transport across placenta
- may result in 80% O2 saturation
How is respiration initiated in the NB?
1) fetal plasma levels of catecholamines and cortisol increase during labor
2) stimulates reabsorption of lung fluid (vs secretion before)
What effect does the first active breath have?
1) assists w/ conversion from fetal to adult circulation
2) further empties lungs of fluid
3) establishes neonatal lung volume and characteristics of pulmonary function
4) decreases pulmonary artery pressure
At which gestational age is there sufficient surfactant?
34wks
What is the function of surfactant?
- reduces surface tension at air/liquid interface in alveoli
- stabilizes alveolar walls so they don’t collapse at end of each breath
What stimulates release of surfactant?
lung expansion
Define functional residual capacity
gas volume left in lungs at end of each expiration
What helps maintain functional residual capacity in a NB?
- crying –> slower expiration
- diaphragm
What keeps the ductus arteriosus open?
1) placental prostaglandin
2) prostacyclin
3) low O2 tension
What occurs at birth to the ductus arteriosus?
constriction!
- blood from R ventricle enters pulmonary circulation
- facilitated by oxygenated blood that otherwise flowed past it
When does the ductus arteriosus close?
w/in 48h
What is the effect of cord clamping on NB circulation?
- stops low pressure fetal-placental circulation –> NB circulation = closed system
+ first breaths –> decreased pulmonary vascular resistance + increased systemic vascular resistance –> blood flow to pulmonary system
Which substances facilitate vasodilation?
1) prostacyclins
2) nitric oxide
3) O2
What lowers pulmonary vascular resistance in the NB?
1) physical lung expansion
2) release of prostacyclins and nitric oxide
3) increased O2 tension
What stimulates release of prostacyclins and nitric oxide?
1) shearing forces on endothelium w/ increased pulmonary blood flow
2) artery distention –> bradykinin release –> prostacyclin and NO release
Define asphyxia
state of extreme O2 deficiency and CO2 excess
What are the consequences of asphyxia?
1) metabolic acidosis
2) signs of organ failure
What are various issues that can exacerbate asphyxia and result in respiratory depression in the NB?
1) acute interruption of umbilical blood flow (e.g. cord compression)
2) premature placental separation
3) maternal hypotension or hypoxia
4) the above superimposed on chronic uteroplacental insufficiency
5) failure to execute proper resuscitation
6) maternal use of anesthetics/analgesics
7) mode and difficulty of delivery
8) maternal health
9) prematurity
Define ductus venosus
shunts blood from umbilical vein to inferior vena cava –> allows blood to bypass fetal liver
Define ductus arteriosus
shunts blood from pulmonary artery to descending aorta –> allows oxygenated blood to bypass fetal lungs
Define foramen ovale
shunts blood from right to left atria–> allows blood to bypass fetal lungs
Define umbilical artery
2 arteries in cord –> deoxygenated blood from fetus to placenta
Define umbilical vein
carries oxygenated blood from placenta to fetus
What causes the ductus venosus to close?
lack of blood return from placenta
What causes the foramen ovale to close?
increased pulmonary blood flow –> increased venous return to L atrium –> increased L atrial pressure –> stents foramen ovale closed
When should the foramen ovale close?
soon after birth
What are NB sources of heat?
1) non-shivering thermogenesis = primary method
2) oxidative glucose, fat, and protein metabolism
3) voluntary muscle activity
4) shivering
Describe non-shivering thermogenesis
- birth = cold –> triggers hypothalamus to oxidize stored lipids in brown fat –> heat production
- warms blood before circulating to peripheral areas
- in NBs w/ hypoglycemia or thyroid dysfunction –> ineffective use of brown fat
What is a normal NB axillary temp?
- 5 - 37.5 C
97. 5 - 99.3 F
What are the 4 mechanisms of heat loss?
1) convection = transfer of heat through air
2) conduction = transfer of heat to cooler surfaces
3) radiation = transfer of heat via thermal waves to cooler surfaces not in direct contact
4) evaporation = loss of heat from evaporation of moisture
How should NB temperature be maintained?
1) skin-to-skin = best!
2) drying, bundling
3) warmer
4) postpone first bath
5) cute lil’ hat!
What factors predispose the NB to hypothermia?
1) large surface
2) limited subQ fat insulation
3) limited ability to generate heat via shivering
4) immature permeable skin
5) wet w/ amniotic fluid
What are s/sx of NB issues w/ thermogenesis?
1) low core temp + cold skin
2) pale skin, pallor
3) hypotonia
4) lethargy, irritability
5) poor feeding
6) vomiting
7) tachypnea
8) increased HR
9) shivering = severe cold stress
Describe how hypothermia can result in hypoglycemia
increased metabolic rate –> increased use of glucose –> hypoglycemia
Describe how hypothermia can result in respiratory distress/hypoxia
hypoglycemia –> decreased surfactant production –> respiratory distress
inc O2 consumption –> anaerobic metabolism –> lactic acid production –> metabolic acidosis –> decreased surfactant production –> respiratory distress
Describe how hypothermia can result in metabolic acidosis
brown adipose tissue metabolism –> anaerobic metabolism –> lactic acid production –> metabolic acidosis
What 4 systems undergo the greatest change during the transition from intra to extrauterine life?
1) respiratory
2) circulatory
3) thermoregulatory
4) glucose metabolism
Upon what are circulatory changes in the NB dependent?
respiratory transition and oxygenation
What are low thresholds for NB glucose levels?
1-2h: 28 mg/dL
3-23h: 40 mg/dL
24-47h: 41 mg/dL
48-72h: 48 mg/dL
How are the three ways in which NBs receive glucose?
1) breastmilk/formula
2) glycogenolysis = breakdown of fetal glycogen stores in liver
3) gluconeogenesis
What are the benefits of vernix?
Antimicrobial proteins and peptides…
1) moisturizes skin
2) keeps skin acidic –> inhibits growth of pathogens
How much glucose do NBs need?
4-8 mg/kg/min
What are s/sx of hypoglycemia in the NB?
1) jitteriness
2) irritability
3) lethargy
4) poor feeding
What NB blood glucose level requires further intervention?
<45-50 mg/dL
confirm w/ venous sample and inform pediatric provider
Define APGAR
0, 1, or 2 pts
Appearance (skin color) Pulse Grimace (reflex irritability) Activity (tone) Respiration
7-10 = vigorous 4-6 = some resuscitation needed <3 = intense resuscitation needed
When does the NB no longer experience the Moro reflex?
2-4 months
