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My Peds > Quiz 1- Fetal Circulation > Flashcards

Quiz 1- Fetal Circulation Flashcards

1
Q

Why are the lungs prone to collapse in the infant?

A
  • weak elastic recoil
  • weak intercostal muscles
  • intrathoracic airways collapse during expiration
  • high closing volumes encroach on FRC
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2
Q

What is a very important thing to do to prevent lung collapse in the neonate?

A

PEEP of 5 cmH2O during anesthesia—> even while spontaneous bagging

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3
Q

What is the primary event of respiratory system transition in infants?

A

The initiation of ventilation

- infant must generate high negative pressure, - 70mmHg, to inflate lungs

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4
Q

What is normal FRC for an infant?

A

25-30 ml/kg

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5
Q

What is the most common and universal sign of respiratory distress in an infant?

A

Tachypnea

Then nasal flaring, retractions, grunting, sea saw breathing, head bobbing

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6
Q

Hypercapnia causes a stress response in an infant. What are clinical symptoms of stress?

A
  • tachycardia- the degree of tachycardia shows the degree of stress
  • HTN
  • worried, anxious look on face
  • diaphoresis
  • agitation, inability to console
  • somnolence and cyanosis are late signs—> impending arrest
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7
Q

T/F chemoreceptors are not active until birth

A

True

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8
Q

The response to hypoxia is biphasic: meaning, initial __________ followed by ~2 min ______ _______.

A

Hyperpnea

Respiratory depression

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9
Q

What 2 things abolish the initial hypereneic response?

A

HYPOTHERMIA

LOW LEVELS OF ANESTHETIC GAS

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10
Q

The ___________ the child the _________ they crash.

A

Smaller

Faster

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11
Q

Hypoxia actually depresses the neonates response to hypercapnia. At what age does hypoxia start to produce sustained hyperventilation?

A

By 3 weeks of age

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12
Q

Hypoxia does what to the heart rate of infant?

A

Causes PROFOUND bradycardia

If HR ≤ 60 start CPR

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13
Q

If you are not ventilating a baby you will see bradycardia within __________.

A

1 minute

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14
Q

What percentage of muscle fibers in the diaphragm of an infant are type 1 (fatigue resistant) compared to the adult?

A

25% type 1 in infants
55% type 1 in adults

Infant will fatigue much quicker

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15
Q

What contributes to apnea of infancy?

A
  • increased O2 consumption (6mL/kg)
  • decreased FRC
  • increased closing volume
    —> once hypoxic, will see abnormal breathing patterns and apnea much sooner than older children and adults
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16
Q

Why do CV shunts exist?

A
  • to minimize blood flow to lungs

- to maximize blood flow/O2 delivery to organ systems

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17
Q

Oxygenated blood is delivered to the fetus via the umbilical vein.
What is the PaO2 in the umbilical vein?

A

35mmHg

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18
Q

What percentage of blood does the ductus venosus divert from the liver and into the IVC?

A

~ 50%

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19
Q

Pulmonary vascular resistance is ________, until umbilical cord is cut.

A

HIGH

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20
Q

Blood entering the descending aorta returns to the ________ AND feeds the _______ _________.

A

Placenta

Lower body

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21
Q

What is the PaO2 of blood in the descending aorta and eventually umbilical arteries?

A

22mmHg

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22
Q

Since a PFO allows arterial and venous circulation to mix, what must you be very vigilant about in infants?

A

Air in IV line

23
Q

What happens once the umbilical cord is cut?

A

SVR increases

Reversal of shunts

24
Q

What takes place at the onset of breathing?

A

PVR decreases and shunts are reversed

  • increases arterial and alveolar PO2- which dilates pulmonary vasculature
  • PVR decreases dramatically
  • pulmonary blood flow increases 450%
  • LA pressure increases, RA pressure decreases
    • foramen ovale closes
25
Q

What percentage of adults have a PFO?

A

25-30%

26
Q

The ductus arteriosis constricts within several minutes of the onset of breathing due to what 2 factors?

A
  • increased PO2
  • decreased circulating prostaglandins
    This causes the ductus venosus to become fibrous over time and close
27
Q

What is given to CV kids to keep shunts open?

A

Prostaglandins

28
Q

What is Persistent Pulmonary hypertension of the newborn (PPHN)?

A
  • persistent fetal shunting beyond normal transition period in the absence of structural heart defect
  • since shunts are not anatomically closed immediately after birth
29
Q

What are some consequences of PPHN?

A
  • increased PVR
  • pulmonary HTN
  • decreased pulmonary blood flow
  • RAP > LAP
  • increased ductal flow
    —> can open foramen ovale
30
Q

What are S/S of PPHN?

A
  • marked cyanosis
  • tachypnea
  • acidosis
    —> RT-lt shunt across FO and DA = cyanotic shunt
31
Q

Before anatomical closure of shunts, transient rt-lt shunting may occur in normal neonates during:

A
  • coughing
  • bucking
  • straining during anesthesia induction or emergence
32
Q

What is the treatment for PPHN?

A
  • hyperventilation - maintain alkalosis
  • pulmonary vasodilators- prostaglandins
  • minimal handling
  • avoidance of stress
  • *** adequate ventilation and oxygenation is key! **
33
Q

What is the tidal volume for the neonate and child up to 12 years?

A

10mL/kg (use IBW if obese)

34
Q

What is the major function of the fetal renal system?

A

Passive production of urine, which contributes to formation of amniotic fluid

35
Q

What is important about amniotic fluid?

A
  • important for normal development of fetal lung

- acts as shock absorber for fetus

36
Q

What are characteristics of the fetal kidney?

A
  • low renal blood flow

- low GFR

37
Q

Why is there such low blood flow and GFR in fetal kidneys?

A
  • structurally immature- size and # of glomeruli
  • low systemic arterial pressure
  • high renal vascular resistance
  • low permeability o f glomerular capillaries
38
Q

How do transitional changes in the newborn affect the renal system?

A
  • systemic arterial pressure increases
  • renal vascular resistance decreases
  • increase in size and function occur through maturity
39
Q

At which gestational age are all nephrons developed?

A

34 weeks
A premature infant has incomplete renal development
—» post conceptual age matters here

40
Q

What contributes to neonates being “obligate Na+ losers” ?

A
  • normal RAAS- facilitates Na+ reabsorption in distal tubules BUT
  • immature neonatal tubules—> do not completely reabsorb Na+ under the stimulus of aldosterone
    —> result is neonate will continue to excrete Na+ even in the presence of severe Na+ deficit
41
Q

What are the urine Na+ levels for adults and neonates?

A

Adult: 5-10mEq/L
Neonates: 20-25mEq/L

42
Q

What is the consequence of Na+ loss in neonates?

A

3rd spacing
RAAS is the primary compensatory mechanism for reabsorption of Na and water losses of plasma, blood, GI tract fluid and 3rd spacing

43
Q

What IVF should be used as maintenance and replacement fluid in neonates?

A
  • maintenance fluid: usually D5 .2% NS

- replacement fluid: LR or NS

44
Q

** What is the lowest acceptable Hg/Hct for neonates and infants due to high O2 demand and limited ability to increase CO?

A

Hct 35%

Hgb > 10

45
Q

** What other reasons warrant a higher Hgb/Hct in neonates and infants?

A
  • increased blood volume per unit weight

- increased CO per unit weight

46
Q

How much blood volume is in a term baby? Pre-term baby?

A
  • term baby: 90mL/kg

- preterm baby: 100mL/kg

47
Q

What limits neonates thermal range?

A
  • size
  • increased surface area to volume ratio
  • increased thermal conductance
    —> their ability to thermo regulate is limited and easily overwhelmed
48
Q

T/F Despite poikilothermic behaviors infants are homeotherms.

A

True

49
Q

What are the 2 stages of heat loss?

A

1.) internal heat gradient: transfer of heat from body core to skin surface
2.) external heat gradient: dissipation of heat from skin surface to environment
—> both stages are governed by the laws of convection, conduction, radiation, evaporation

50
Q

How can heat loss be prevented?

A
  • CONDUCTION: (cutaneous blood flow/am cutaneous tissue
    Make sure surface they lay on is warm
    • short cases: warm blankets
    • longer cases: heating mattress or bear hugger
  • CONVECTION: (air temp, air velocity and volume of air flow)
    Decrease air movement across body
  • most NICU ORs are kept at 80ËšF
  • RADIATION: (temperature gradient b/t skin and surrounding surfaces, total radiating surface of infant)
    ** major source of heat loss **
    Warm OR room, radiant lamps “French fry lights”
  • EVAPORATION: (relative humidity, minute ventilation)
    Cover exposed body cavities
    Heat and humidify inspired gases
51
Q

How is heat production achieved in the infant?

A
  • voluntary muscle activity
  • involuntary muscle activity
  • NON-SHIVERING THERMOGENISIS—> major component in neonate
52
Q

What is non-shivering thermogenesis?

A

Metabolism of brown fate that occurs with cold stress
Mediated by SNS stimulation
Heat is a product of fatty acid metabolism

53
Q

What are some facts about brown fat?

A
  • develops b/t 26-30 weeks gestation
  • 2-6% of neonatal total body weight
  • abundant vascular supply and rich innervation of SNS
54
Q

Where can brown fate be found?

A
  • mediastinum
  • b/t scapula
  • around adrenals and axilla

My Peds (6 decks)

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