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Advanced Principles A (Spring 2024) > Uteroplacental & Fetal Physiology Pt. 1 (Exam II) > Flashcards

Uteroplacental & Fetal Physiology Pt. 1 (Exam II) Flashcards

1
Q

What does UBF stand for?

A

Uterine Blood Flow

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2
Q

What does IUGR stand for?

A

Intrauterine Growth Restriction

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3
Q

What does PIH stand for?

A

Pregnancy Induced Hypertension

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4
Q

What does Gravida mean?

A

of pregnancies

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5
Q

What does Para mean?

A

of live births or >20 weeks

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6
Q

What does P50 mean?

A

Oxygen level at which Hgb is 50% saturated

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7
Q

What does HbF stand for?

A

Fetal Hemoglobin

HbA = Adult Hgb

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8
Q

Uterine perfusion increases or decreases throughout gestation?

A

Increases

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9
Q

What is uterine blood flow at term?
What percentage of CO is this?

A

~ 700 ml/min

~ 12% of CO

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10
Q

Pregnancy is ____ resistance, but _____ flow.

A

Low Resistance, High Flow

Vasodilation w/ ↑ volume & CO

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11
Q

What is the primary source of uterine blood flow?

A

Uterine Arteries that branch from internal iliac (hypogastric) arteries

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12
Q

What is the secondary source of uterine blood flow?

A

Ovarian Arteries that branch from the aorta at the L4 level

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13
Q

70 - 90% of uterine blood flow will pass through the ________ space.

A

Intervillous space

Low resistance area of maternal blood pooling for exchange of gas nutrients.

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14
Q
A
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15
Q

Uterine blood flow = __________ ?

Formula for uterine blood flow.

A

Uterine perfusion pressure ÷ Uterine vascular pressure

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16
Q

Uterine perfusion pressure = __________?

A

Uterine arterial pressure - uterine venous pressure

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17
Q

What is the mechanism for autoregulation of UBF during pregnancy?

A

Trick question. There is no autoregulation of UBF. Entirely dependent on maternal blood pressure.

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18
Q

What are the overarching causes of decreased UBF?

A
  • ↓ uterine arterial pressure
  • ↑ uterine venous pressure
  • ↑ uterine vascular resistance
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19
Q

What position would compromise uterine arterial pressure?

A

Supine due to aortocaval compression

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20
Q

Hypovolemia will result in decreased _________ and thus decreased UBF.

A

decreased uterine arterial pressure

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21
Q

How will neuraxial anesthesia affect UBF?

A

Sympathetic blockade → hypotension → decreased uterine arterial pressure = ↓ UBF

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22
Q

What should be administered prior to epidural placement?

A

Fluid bolus to counteract hypotension.

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23
Q

How will supine positioning affect uterine venous pressure?

A

↑ venous pressure due to IVC compression

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24
Q

How will contractions effect uterine venous pressure?

A
  • Contractions = ↑ venous pressure
  • Tachysystole (Lots of strong contractions in short term.)
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25
Q

What drugs will cause a tachysystolic state?

A
  • Oxytocin
  • Cocaine/Meth
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26
Q

What occurs with uterine blood flow during uterine relaxation? (such as after a contraction)

A

Hyperemia (increased blood flow)

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27
Q

What factors will increase uterine vascular resistance?

A
  • Endogenous vasocontrictors (catecholamines from stress response)
  • Exogenous catecholamines (Phenylephrine & Ephedrine)
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28
Q

Is phenylephrine or ephedrine preferred for parturient patients?

A

Phenylephrine

Ephredrine can be used but crosses placental barrier and increases fetal metabolic requirements.

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29
Q

High concentrations of local anesthetics will have what effect on uterine blood flow?

A

↓ UBF from high LA’s from:

  • Arterial constriction
  • Inhibition of endothelial vasodilation
  • Stimulation of myometrial contraction
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30
Q

How does epinephrine, administered neuraxially, affect UBF?

A
  • No change in healthy patients
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31
Q

What test dose of epinephrine is used in neuraxial anesthesia for parturient patients?

A

10 - 15 mcg

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32
Q

How do clonidine and precedex affect UBF when administered:
Neuraxially?
Intravenously?

A
  • Neuraxial = No change in UBF
  • IV = ↓ UBF
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33
Q

Neuraxial anesthesia will increase UBF if _________ is avoided.

A

hypotension

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34
Q

How do volatile anesthetics affect UBF?

A

↓ UBF if MAC > 1.5 (obviously rare)

Minimal effect on UBF with MAC 0.5 - 1.5

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35
Q

The chorionic plate of the placenta faces the _____.

A

fetus

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36
Q

The basal plate of the placenta faces the _______.

A

mother

37
Q

What are the functions of the placenta?

A
  • Production of proteins, hormones, enzymes
  • Gas exchange
  • Nutrient & waste exchange
38
Q

What is the intervillous space?

A

Large placental sinus with multiple folds

39
Q

The intervillous space is a high resistance area. T/F?

A

False. The intervillous space is a low resistance area.

40
Q

How much blood is in the intervillous space at one time?

A

350mls

41
Q

Where does blood enter into the intervillous space from?

A

spiral arteries

42
Q

The umbilical vein carries __________ blood.

A

oxygenated

43
Q

The umbilical arteries (two in number) carry ________ blood.

A

deoxygenated

44
Q

What variables change the rate and amount of transfer of (drugs, toxins, O₂, CO₂, etc.) in the intervillous space?

A
  • Concentration gradient
  • Permeability
  • Restriction of movement (some substances are bound to in the placental tissue to prevent fetal uptake)
45
Q

What substances/drugs move via passive diffusion?

A
  • O₂
  • CO₂
  • Most anesthetic drugs
46
Q

In regards to facilitated diffusion, a higher temperature will ______ rate of diffusion.

A

increase

47
Q

What’s an example of a molecule that moves via facilitated diffusion?

A

Glucose

48
Q

Active transport requires ____.

What is required for active transport?

A

ATP

  • Protein membrane carrier
  • Saturation kinetics
  • Competitive inhibition

ex. Na⁺, K⁺, Ca⁺⁺

49
Q

What transfer mechanism is characterized by membrane rearrangement, vesicle formation, and the movement of large macromolecules?

A

Pinocytosis

50
Q

What is an example of pinocytosis transfer in pregnancy?

A

Transfer of IgG from mother to fetus

51
Q

What are the major factors that impact drug transfer across the placenta?

A
  • Blood flow
  • Lipid solubility
  • Protein binding
  • pKa & pH/charge
  • Molecular size

(Also, gestational age, maternal factors, and placental drug metabolism).

52
Q

What is the primary factor affecting anesthetic drug delivery across the placenta? Why?

A

Blood flow because most drugs are passively transferred.

53
Q

High lipid solubility results in _______ bilayer penetration.

A

more

54
Q

What drug is an example of high lipid solubility resulting in placental tissue trapping of the drug?

A

Sufentanil

55
Q

Why are bupivacaine and ropivacaine less likely to cross the placenta?

A

Both are highly protein-bound.

56
Q

Albumin binds to _____ and ________ compounds.

A

acidic & lipophillic

57
Q

α-1 acid glycoprotein binds to ______ compounds.

A

basic

58
Q

What is pKa?

A

The pH at which 50% of a drug is ionized & 50% is non-ionized

59
Q

Do ionized or non-ionized drugs tend to cross the placenta more easily?

A

non-ionized

60
Q

What is ion-trapping?

A

When the fetus has a lower pH than the mother resulting in drugs being trapped in fetal circulation via H⁺ binding to non-ionized drug.

61
Q

What are examples of highly ionized drugs that don’t cross the placenta easily?

A
  • LA’s
  • Opioids
  • Succinylcholine
62
Q

Drugs with a molecular weight of ________ typically cross the placenta.

A

< 500 Da (Daltons)

63
Q

Most drugs with a molecular weight of _______ do not cross the placenta.

A

> 1000 Da (Daltons)

64
Q

What are examples of drugs that don’t cross the placenta due to their high molecular weight?

A
  • ND NMBD’s
  • Heparin
  • Protamine
65
Q

What anticholinergics readily cross the placenta?

A
  • Atropine
  • Scopolamine
66
Q

What anti-hypertensives readily cross the placenta?

A
  • β blockers
  • Nitroprusside
  • Nitroglycerin
67
Q

What local anesthetic can readily cross the placenta? (in contrast to other LA’s)

A

Lidocaine

68
Q

What drug classes typically are able to readily cross the placenta?

A
  • Anticholinergics
  • Anti-hypertensives
  • VAA’s
  • Benzo’s
  • Ephedrine
  • Induction agents
  • Tylenol
  • Neostigmine
  • Warfarin
69
Q

What drugs DO NOT readily cross the placenta?

A
  • Glycopyrrolate
  • Heparin
  • Succinylcholine
  • NDNMBD’s
  • Sugammadex*
  • Phenylephrine
70
Q

What drugs should be used to reverse paralysis in pregnant patients? Why?

A

Neostigmine & Atropine

Glyco does not cross the placenta, thus neostigmine will cause severe fetal bradycardia in conjunction with neostigmine. Use atropine to avoid this.

71
Q

What is a teratogen?

A

Substance that increases the risk of a fetal defect

72
Q

When during development are teratogens most likely to cause fetal defect?

A

15 - 60 days gestational age

73
Q

Which anesthetics drugs are proven teratogens?

A

None

However, we like to minimize or eliminate fetal exposure to anesthesia in the 15 - 60 days gestational period.

74
Q

What drug that we commonly use is not regulated by the FDA?

A

N₂O (medical gas, not drug)

75
Q

What is the teratogenicity profile of benzodiazepines?

A
  • Probable cleft palate formation from GABA activity
  • Chronic exposure (not a one time low dose)

Especially Diazepam.

76
Q

How does meperidine effect the fetus?

A
  • Neonate CNS depression
  • Can cause seizures due to normeperidine accumulation
77
Q

How does morphine affect the fetus?

A
  • ↓ maternal respirations = ↓ fetus O₂
  • fewer fetal heart rate accelerations
78
Q

What opioid can be really useful for maternal sedation? Why?

A

Remifentanil

Rapid metabolism = minimal fetal exposure.

79
Q

What is P50 ?

A

The partial pressure of O₂ at which Hgb is 50% saturated with O₂

80
Q

At ____ mmHg of partial pressure of oxygen, 50% of fetal hgb are saturated.

A

19mmHg

81
Q

What is the P50 of adult Hgb?

A

27 mmHg PO2

82
Q

How does the P50 of HbF compare to that of HbA?

A

HbF = 19 mmHg
HbA = 27 mmHg

HbF will preferentially pick up O₂ from the mother’s blood.

83
Q

A lower P50 will result in a ________ affinity.

A

higher

84
Q

What concept is linked with the increase of CO₂ and decrease of pH resulting in a _______ affinity of Hgb for oxygen.

A

Bohr Effect

decreased affinity

85
Q

The presence of CO₂ and blood acidity in fetal blood will _______ the release of of O₂ from maternal hemoglobin.

A

enhance

Right shift = Release

86
Q

What happens as the CO₂ content of fetal blood decreases?

A

Fetal blood becomes alkaline → curve shifts left → facilitates more O₂ uptake by HbF (increased affinity).

Left shift = Lock

87
Q

How will maternal hyperventilation affect fetal oxygenation?

A

Hyperventilation = hypocapnia/maternal alkalosis → maternal oxyhemoglobin curve shifts left and prevents as much O₂ from getting to the baby

88
Q
A

Advanced Principles A (Spring 2024) (11 decks)

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