Uteroplacental & Fetal Physiology Pt. 1 (Exam II)

Question 1

What does UBF stand for?

Answer 1

Uterine Blood Flow

Question 2

What does IUGR stand for?

Answer 2

Intrauterine Growth Restriction

Question 3

What does PIH stand for?

Answer 3

Pregnancy Induced Hypertension

Question 4

What does Gravida mean?

Answer 4

of pregnancies

Question 5

What does Para mean?

Answer 5

of live births or >20 weeks

Question 6

What does P₅₀ mean?

Answer 6

Oxygen level at which Hgb is 50% saturated

Question 7

What does HbF stand for?

Answer 7

Fetal Hemoglobin

HbA = Adult Hgb

Question 8

Uterine perfusion increases or decreases throughout gestation?

Answer 8

Increases

Question 9

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

Answer 9

~ 700 ml/min

~ 12% of CO

Question 10

Pregnancy is ____ resistance, but _____ flow.

Answer 10

Low Resistance, High Flow

Vasodilation w/ ↑ volume & CO

Question 11

What is the primary source of uterine blood flow?

Answer 11

Uterine Arteries that branch from internal iliac (hypogastric) arteries

Question 12

What is the secondary source of uterine blood flow?

Answer 12

Ovarian Arteries that branch from the aorta at the L4 level

Question 13

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

Answer 13

Intervillous space

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

Question 14

Uterine blood flow = __________ ?

Formula for uterine blood flow.

Answer 14

Uterine perfusion pressure ÷ Uterine vascular pressure

Question 15

Uterine perfusion pressure = __________?

Answer 15

Uterine arterial pressure - uterine venous pressure

Question 16

What is the mechanism for autoregulation of UBF during pregnancy?

Answer 16

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

Question 17

What are the overarching causes of decreased UBF?

Answer 17

• ↓ uterine arterial pressure
• ↑ uterine venous pressure
• ↑ uterine vascular resistance

Question 18

What position would compromise uterine arterial pressure?

Answer 18

Supine due to aortocaval compression

Question 19

Hypovolemia will result in decreased _________ and thus decreased UBF.

Answer 19

decreased uterine arterial pressure

Question 20

How will neuraxial anesthesia affect UBF?

Answer 20

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

Question 21

What should be administered prior to epidural placement?

Answer 21

Fluid bolus to counteract hypotension.

Question 22

How will supine positioning affect uterine venous pressure?

Answer 22

↑ venous pressure due to IVC compression

Question 23

How will contractions effect uterine venous pressure?

Answer 23

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

Question 24

What drugs will cause a tachysystolic state?

Answer 24

• Oxytocin
• Cocaine/Meth

Question 25

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

Answer 25

Hyperemia (increased blood flow)

Question 26

What factors will increase uterine vascular resistance?

Answer 26

- Endogenous vasocontrictors (catecholamines from stress response) - Exogenous catecholamines (Phenylephrine & Ephedrine)

Question 27

Is phenylephrine or ephedrine preferred for parturient patients?

Answer 27

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

Question 28

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

Answer 28

↓ UBF from high LA's from: - Arterial constriction - Inhibition of endothelial vasodilation - Stimulation of myometrial contraction

Question 29

How does epinephrine, administered neuraxially, affect UBF?

Answer 29

- No change in healthy patients

Question 30

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

Answer 30

10 - 15 mcg

Question 31

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

Answer 31

- Neuraxial = No change in UBF - IV = ↓ UBF

Question 32

Neuraxial anesthesia will increase UBF if _________ is avoided.

Answer 32

hypotension

Question 33

How do volatile anesthetics affect UBF?

Answer 33

↓ UBF if MAC > 1.5 (obviously rare) Minimal effect on UBF with MAC 0.5 - 1.5

Question 34

The chorionic plate of the placenta faces the _____.

Answer 34

fetus

Question 35

The basal plate of the placenta faces the _______.

Answer 35

mother

Question 36

What are the functions of the placenta?

Answer 36

- Production of proteins, hormones, enzymes - Gas exchange - Nutrient & waste exchange

Question 37

What is the intervillous space?

Answer 37

Large placental sinus with multiple folds

Question 38

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

Answer 38

False. The intervillous space is a low resistance area.

Question 39

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

Answer 39

350mls

Question 40

Where does blood enter into the intervillous space from?

Answer 40

spiral arteries

Question 41

The umbilical vein carries __________ blood.

Answer 41

oxygenated

Question 42

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

Answer 42

deoxygenated

Question 43

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

Answer 43

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

Question 44

What substances/drugs move via passive diffusion?

Answer 44

- O₂ - CO₂ - Most anesthetic drugs

Question 45

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

Answer 45

increase

Question 46

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

Answer 46

Glucose

Question 47

Active transport requires ____. What is required for active transport?

Answer 47

ATP - Protein membrane carrier - Saturation kinetics - Competitive inhibition ex. Na⁺, K⁺, Ca⁺⁺

Question 48

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

Answer 48

Pinocytosis

Question 49

What is an example of pinocytosis transfer in pregnancy?

Answer 49

Transfer of IgG from mother to fetus

Question 50

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

Answer 50

- **Blood flow** - Lipid solubility - Protein binding - pKa & pH/charge - Molecular size (Also, gestational age, maternal factors, and placental drug metabolism).

Question 51

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

Answer 51

Blood flow because most drugs are passively transferred.

Question 52

High lipid solubility results in _______ bilayer penetration.

Answer 52

more

Question 53

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

Answer 53

Sufentanil

Question 54

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

Answer 54

Both are **highly protein-bound**.

Question 55

Albumin binds to _____ and ________ compounds.

Answer 55

acidic & lipophillic

Question 56

α-1 acid glycoprotein binds to ______ compounds.

Answer 56

basic

Question 57

What is pKa?

Answer 57

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

Question 58

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

Answer 58

non-ionized

Question 59

What is ion-trapping?

Answer 59

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.

Question 60

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

Answer 60

- LA's** - Opioids** - Succinylcholine but it’s too big.

Question 61

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

Answer 61

< 500 Da (Daltons)

Question 62

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

Answer 62

> 1000 Da (Daltons)

Question 63

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

Answer 63

- ND NMBD's - Heparin - Protamine

Question 64

What anticholinergics readily cross the placenta?

Answer 64

- **Atropine** - Scopolamine

Question 65

What anti-hypertensives readily cross the placenta? 3

Answer 65

- β blockers - Nitroprusside - Nitroglycerin

Question 66

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

Answer 66

Lidocaine

Question 67

What drug classes typically are able to readily cross the placenta? 9

Answer 67

- Anticholinergics (Atropine) - Anti-hypertensives - Benzo's - Induction agents - VAA's - **Neostigmine** - Ephedrine - Tylenol - Warfarin

Question 68

What drugs **DO NOT** readily cross the placenta? 6

Answer 68

- **Glycopyrrolate** - Heparin (too big) - Succinylcholine (highly ion) - NDNMBD's (too big) - Sugammadex* (not recommended) - Phenylephrine

Question 69

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

Answer 69

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

Question 70

What is a teratogen?

Answer 70

Substance that increases the risk of a fetal defect

Question 71

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

Answer 71

15 - 60 days gestational age

Question 72

Which anesthetics drugs are proven teratogens?

Answer 72

**None** However, we like to minimize or eliminate fetal exposure to anesthesia in the 15 - 60 days gestational period.

Question 73

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

Answer 73

N₂O (medical gas, not drug)

Question 74

What is the teratogenicity profile of benzodiazepines?

Answer 74

- Probable cleft palate formation from GABA activity - Chronic exposure (not a one time low dose) *Especially Diazepam*.

Question 75

How does meperidine effect the fetus?

Answer 75

- Neonate CNS depression - Can cause seizures due to normeperidine accumulation

Question 76

How does morphine affect the fetus?

Answer 76

- ↓ maternal respirations = ↓ fetus O₂ - fewer fetal heart rate accelerations

Question 77

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

Answer 77

Remifentanil *Rapid metabolism = minimal fetal exposure*.

Question 78

What is P₅₀ ?

Answer 78

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

Question 79

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

Answer 79

19mmHg

Question 80

What is the P₅₀ of adult Hgb?

Answer 80

27 mmHg PO2

Question 81

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

Answer 81

HbF = 19 mmHg HbA = 27 mmHg HbF will preferentially pick up O₂ from the mother's blood.

Question 82

A lower P₅₀ will result in a ________ affinity.

Answer 82

higher

Question 83

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

Answer 83

Bohr Effect decreased affinity

Question 84

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

Answer 84

enhance ***R**ight shift = **R**elease*

Question 85

What happens as the CO₂ content of fetal blood decreases?

Answer 85

Fetal blood becomes alkaline → curve shifts left → facilitates more O₂ uptake by HbF (increased affinity). *Left shift = Lock*

Question 86

How will maternal hyperventilation affect fetal oxygenation?

Answer 86

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