Lecture 1 Flashcards
What is transition?
The change from fetal to extra-uterine life
Pre-term is?
Prior to 37 weeks gestational age
Neonate is?
1 - 28 days of life
Infant is?
28 days to 1 year of life
Child is?
> 1 year of life
Puberty is?
Age 13 or 14 years of age (teens)
When is the most significant part of transition?
Within the first 24 - 72 hours after birth
Which way does fetal Hgb shift the oxyhemoglobin dissociation curve? What does this mean?
Left = increased O2 loading in the lungs/placenta, decreased O2 unloading at tissues
What is the Hgb of a full term neonate?
18-20 g/dL
What happens at 4 weeks fetal lung development?
Primitive lung buds develop from foregut
What happens at 16 weeks fetal lung development?
Branching of bronchial tree complete 28 divisions (no further formation of cartilaginous airways)
What happens at 24 weeks fetal lung development?
Primitive alveoli (succulent) and type II cells present; surfactant possible
At how many weeks is survival possible with artificial ventilation of a preterm baby?
24 weeks
What happens at 28-30 weeks fetal lung development?
Capillary network surrounds succules
At how many weeks can a preterm baby survive WITHOUT support?
28-30 weeks
What happens at 36 - 40 weeks fetal lung development?
True alveoli present, roughly 2 million at birth
What happens to lung development from birth to 3 mos?
PaO2 rises as R to L mechanical shunts close
How many alveoli are present at 6 years of life?
350 million
When does “Guppy breathing” start in uterine?
30 weeks gestation
What has been proven to lead to fetal lambs NOT breathing?
Diaphragm denervation, NOT chemoreceptors
What is the current view on how rhythmic breathing starts in fetal lambs?
Clamping of the umbilical cord and increasing O2 tensions
At birth what are baby’s blood gases (in general)?
Acidotic, low PaO2 and high PaCO2
At 24 hours what are baby’s blood gases (in general)?
Normalized pH, PaO2, and PaCO2
What is the primary event of the respiratory system transition at birth? What happens to alveoli?
Initiation of ventilation —> alveoli go from fluid-filled to air-filled
What happens as a result of increased PO2 and decreased CO2 at birth?
DECREASE pulmonary vascular resistance —> pulmonary blood flow increases allowing gas exchange to occur
What pressure to infants need to generate to inflate lungs
-70 cm H2O
What is infant FRC?
Approximately 25-30 ml/kg
Why don’t infants lungs collapse all of the time?
Terminate expiratory phase of breathing BEFORE reaching their true FRC —> creates intrinsic PEEP and a higher FRC
**What should be done to prevent neonate lung collapse during artificial ventilation and anesthesia?
Add PEEP of 5 cm H2O
When is respiratory control normal and better developed i infants?
At 3-4 weeks
What depresses a neonate’s response to CO2?
Hypoxia
What abolishes a neonate’s initial hyperpneic Response?
Hypothermia and low levels of anesthetic gases
How is apnea defined for infants?
Respiratory pauses exceeding 20 seconds or those accompanied by bradycardia or cyanosis
What does hypoxia cause in babies?
Profound bradycardia
What percent of infant diaphragm muscle fibers are Type I fatigue-resistant? Adults?
25% in infants; 55% in adults
What is the O2 consumption rate of an infant?
6 mL/kg
Where does gas exchange occur in the fetus?
Placenta
What are the 3 intracardiac shunts of the fetus? Purpose?
- Ductus Venosus; 2. Ductus Arteriosus; Foramen Ovale —> to minimize blood flow to lungs while maximizing flow/O2 delivery to organ systems
Is fetal circulation parallel or series? What about transitional circulation?
Fetal circulation = parallel; transitional = series
What 2 things happen at birth that reverse shunts?
- Cut umbilical cord - INCREASES SVR; 2. Onset of breathing = DECREASES PVR
Why are babies born blue?
In utero PVR is high and SVR is low
Why do babies “pink up” after birth?
SVR is high and PVR is low —> shunts close
What is persistent pulmonary hypertension of the Newborn (PPHN)?
Persistence of fetal shunting beyond the normal transition period in the absence of structural heart defect
What is etiology of PPHN?
hypoxia and acidosis
What is treatment for PPHN (5)?
Hyperventilation; pulmonary vasodilators; minimal handling; avoid stress; adequate ventilation and oxygenation
What is adequate tidal volume for baby to 10/12 years of age?
10 mL/kg
What is major function of fetal renal system?
Urine contributes to formation of amniotic fluid
What are the characteristics of fetal kidney (2)?
Low renal blood flow and low GFR
When are all nephrons developed?
By 34 weeks
Why is a neonate considered an “obligate sodium loser?”
Because immature tubules do not completely reabsorbed NA under the stimulus of aldosterone
What must newborns IVF have in it?
Sodium, because they cannot conserve Na and will continue to produce dilute urine to the point of dehydration
What is the lowest acceptable Hgb and Hct for a neonate?
Hgb = 10 or more; Hct = 35% or more
What are the 2 stages of heat loss?
- Transfer of heat from body core to skin.surface (internal temperature gradient); 2. Dissipation of heat from skin surface to environment (external heat gradient)
How to prevent conduction heat loss in babies?
Warm blankets, heating mattress, Bair hugger
How to prevent convection heat loss in babies?
Reduce air movement across body survace
How to prevent radiation heat loss in babies?
Warm OR; radiant heat lamps
How to regent evaporation heat loss in babies?
Cover exposed body cavities; heat and humidify inspired gases
How is heat proction and thermal regulation achieved in infants (3)?
- Voluntary muscle activity; 2. Involuntary muscle activity; 3. Non-shivering thermogenesis
What is non-shivering thermogenesis?
Metabolism of brown fat -> prevents babies from shivering
When does brown fat develop? Where is it located?
Between 26-30 weeks gestation; located in the mediastinum, between the scapulae, around the adrenals and in the axilla
