4. Maternal and Fetal Physiology Flashcards

1
Q

blood travels from the mothers uterine artery to?

A

the placenta

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2
Q

from the placenta where does the blood go?

A

through the umbilical vein into the fetal right atrium

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3
Q

how is blood shunted around the liver in a fetus?

A

ductus venosus

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4
Q

what are the two pathways that blood can travel after being in the fetal right atrium?

A

50% blood shunt through foramen ovale to left atrium

50% blood goes through right ventricle

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5
Q

when blood makes it to the right ventricle what two ways can it go?

A

90% to pulm artery and is shunted to aorta via the ductus arteriosus
10% to the fetal lungs for perfusion

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6
Q

why does most of the blood shunt away from the fetal lungs (other than they aren’t breathing)

A

they have hypoxic vasoconstriction and that decreases the amount of blood that is able to flow through the lungs

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7
Q

how does blood return to the placenta?

A

umbillical artery

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8
Q

foramen ovale

A

hole between RA and LA

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9
Q

what % of the population have a patent foramen ovale?

A

10-25%

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10
Q

how quickly does functional closure of the foramen ovale take after birth?

A

rapidly after first breath

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11
Q

how quickly does anatomic closing of the foramen ovale take after birth?

A

3-12months

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12
Q

ductus arteriosus

A

connection between the pulmonary artery and the aorta

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13
Q

how quickly does functional closure of the ductus arteriosus take after birth?

A

first few days after birth

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14
Q

how quickly does complete closure of the ductus arteriosus take after birth?

A

4-6wk

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15
Q

what % of the population has a patent ductus arteriosus?

A

10%

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16
Q

what drug keep the ductus arteriosus open?

A

prostaglandins PGE1

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17
Q

indomethacin

A

promotes ductus arteriosus closure

treats PDA after birth

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18
Q

NSAIDS and ductus arteriosus

A

promotes closure of ductus arteriosus

contraindicated in third trimester pregnancy

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19
Q

what are the fetal circulation changes at birth?

A
  1. baby breathes = lung expands
  2. PaO2 incr = vasodilation of pulm vasculature
  3. incr pulm blood flow
    incr blood flow to LA
    LAP incr
  4. incr LAP –> foramen ovale close
  5. incr Aortic P –> dectus arteriosus close
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20
Q

what triggers foramen ovale closur

A

incr LAP

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21
Q

what triggers ductus arteriosus closure?

A

incr aortic pressure

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22
Q

Maternal/Fetal blood flow order

A

uterus
uterine artery
placenta
umbilical vein
RA
ductus arteriosus or foramen ovale
aorta/systemic organs
umbilical arteries
placenta
umbilical vein

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23
Q

how much plasma ultrafiltrate do fetal lungs have?

A

90mL

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24
Q

how does the ultrafiltrate get removed from fetal lungs?

A

during SVD it is squeezed out by mothers pelvic muscles

the rest absorbed by pulm capillaries and lymphatics

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25
Q

which are more likely to have problems with respiration after birth? SVD or C-section

A

C-section, no squeeze of ultrafiltrate out

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26
Q

P50

A

PaO2 that will cause SaO2 of 50%

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27
Q

P50 normal adult hemoglobin

A

27mmHg

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28
Q

P50 pregnant mother at term

A

30mmHg

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29
Q

P50 fetal hemoglobin

A

19mmHg

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30
Q

which is more affinitive for oxygen? fetal or maternal hemoglobin?

A

fetal

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31
Q

Aortocaval compression

A

pregnant patient lays supine it compresses aorta and IVC
decrease CO
decrease uterine artery blood flow (fetal hypoxia)

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32
Q

fetal hypoxia etiologies 2

A

1 decrease in uterine blood flow

2 left shift of mothers oxygen Hb curve

33
Q

what can cause decrease in uterine blood flow? 4

A

hypotension
uterine artery vasoconstriction
uterine contractions
aortocaval compression

34
Q

what can cause unterine artery vasoconstriction?

A

hypocapnea (hypervent)

vasoconstrictors

35
Q

symptoms of aortocaval compression

A

maternal hypotension
decreased maternal cardiac output/uterine blood flow
engorged epidural venous plexus

36
Q

supine hypotensive syndrome

A

when a pregnant mother is supine and gets hypotensive

(AKA Aortocaval compression)

37
Q

when is left uterine displacement considered mandatory?

A

patient is more than 20 weeks along

38
Q

stage 1 labor

A

onset of labor to full 10cm dilation

39
Q

where is the pain during the latent phase of stage 1?

A

abdominal area t10-L1

40
Q

where is the pain during the active phase of stage 1? why?

A

perineal pain S2-S4 (pudendal nerve)

fetal head press against pelvis

41
Q

stage 2 labor

A

time of max dilation to delivery of fetus

42
Q

where is the pain during stage 2 labor?

A

perineal area

43
Q

what can heavy respirations in stage 2 labor lead to?

A

hypocarbia

fetal alkalosis

44
Q

stage 3 labor

A

delivery of fetus to delivery of placenta

45
Q

CNS changes for pregnant patient 2

A
  1. decreased MAC requirements (up to 40%)

2. Decreased neuraxial dosing requirements

46
Q

Cardiovascular changes for pregnant patient 6

A
  1. increased blood volume
  2. increased cardiac output
  3. increased clotting factor concentration
  4. decreased SVR
  5. ECG changes (left axis deviation
  6. Iron anemia
47
Q

respiratory changes for pregnant patient 3

A
  1. hyperventilation
  2. rapid oxygen desaturation
  3. significant airway edema
48
Q

GI changes for a pregnant patient 3

A
  1. decreased lower esophageal sphincter tone
  2. increased production of gastric acid
  3. decreased gastric motility
49
Q

ABG changes for a pregnant patient 3

A

increase in PaO2
increase in pH
decrease in HCO3-

50
Q

Renal changes for a pregnant patient 2

A

GFR increases

mild glycosuria/proteinuria is common

51
Q

why is there decreased MAC requirements for pregnant women?

A

endogenous opiods increased

progesterone levels are 20x normal (sedative)

52
Q

why is the neuraxial dosing requirements decreased? 3

A
  1. fetus compresses the IVC
  2. epidural venous engorgement decreases the CSF
  3. spinal and epidural medications have increased cephalad spread
53
Q

what is the approximate blood loss for SVD?

A

400-500mL

54
Q

what is the approximate blood loss for a c-section?

A

800-1000mL

55
Q

what problems does increased blood volume cause?

A

dilutional anemia

edema from diluted albumin

56
Q

is there a greater increase in plasma or RBCs?

A

plasma- thats why there is dilutional anemia

57
Q

what causes the edema?

A

plasma dilutes the albumin and decreases oncotic pressure

58
Q

what are the two reasons why cardiac output increases?

A

decrease in afterload (decrease in SVR)

increase in blood volume

59
Q

why could cardiac output decrease for a pregnant patient?

A

aortocaval compression from laying supine

60
Q

when does the greatest increase in cardiac output occur?

A

immediately after delivery of baby because no more aortocaval compression

61
Q

why is there increased clotting factors?

A

prepares mother for blood loss

62
Q

what risk is increased in the hypercoaguable state?

A

DVT risk (up to 6-12 weeks post partum)

63
Q

what are the safe anticoagulants?

A

heparin

finbrinolytics

64
Q

what is an unsafe anticoagulant?

A

coumadin

65
Q

what causes the decreased SVR?

A

increase in estrogen and progesterone

66
Q

what causes the left axis deviation of the heart?

A

diaphragm elevation shifts the heart

67
Q

what causes iron anemia?

A

fetus consuming Fe

vitamin supplements can be recommended

68
Q

why do pregnant women hyperventilate

A

because increased oxygen requirements= deeper TV

69
Q

what stimulates the deep breaths besides increased O2 requirements?

A

progesterone relaxes bronchial smooth muscle

70
Q

why do mothers have an right shift of the oxyhemoglobin curve?

A

increased 2,3 DPG levels

71
Q

causes of the airway edema in pregnant mothers?

A
weight gain (larger tissues)
decreased oncotic pressure intravasculatly '
progesterone
72
Q

what type of intubation should you avoid in pregnant mothers?

A

nasal intubations

73
Q

why does progesterone cause airway edema??

A

causes capillary engorgement in the upper airway

74
Q

what causes a decreased LES tone?

A

increased progesterone

upward displacement of stomach

75
Q

at what gestational age are pregnant pts considered full stomach

A

full stomach after 16-20 weeks gestational age

76
Q

why is there an increase in PaO2 in pregnant patients?

A

increased MV

77
Q

why is there an increase in pH in pregnant patients

A

respiratory alkalosis

78
Q

why is there a decrease in HCO3- in pregnant patients?

A

compensation for resp alk