Uteroplacental & Fetal Physiology Pt. 1 (Exam 2)

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

number of pregnancies

Question 5

What does Para mean?

Answer 5

number of live births or >20 weeks

Question 6

What does P₅₀ mean?

Answer 6

Oxygen partial pressure level at which Hgb is 50% saturated

Question 7

What does HbF stand for? HbA?

Answer 7

HbF = 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 maternal CO is this?

Answer 9

• ~700 ml/min
• ~12% of CO

Question 10

Pregnancy is ____ resistance, but _____ flow.

Answer 10

Low Resistance, High Flow

Systemic Vasodilation w/ ↑ volume & CO

Question 11

Where does the primary source of uterine blood flow through?

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

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

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

this is why UBF exceeds minimal demand for fetal oxygen (cushion)

Question 17

What are the general 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 position due to aortocaval compression

Question 19

Hypovolemia will result in decreased _________ and thus decreased UBF.

Answer 19

decreased uterine arterial pressure

potentially from hypovolemia or bleeding

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.

typically recommended to co-load, instead of prior administration

Question 22

How will supine positioning affect uterine venous pressure?

Answer 22

↑ venous pressure due to IVC compression ⇒ ↓UBF

Question 23

What is tachysystole?

Answer 23

Condition of the uterus contracting too forcefully or too frequently (usually 5+ contractions in 10min or contraction lasting longer than 60seconds)

Question 24

How will contractions affect uterine venous pressure?

Answer 24

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

Question 25

What drugs can cause a tachysystolic state?

Answer 25

- **Oxytocin** - Cocaine/Meth

Question 26

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

Answer 26

Hyperemia (increased blood flow)

Question 27

What factors will increase uterine vascular resistance?

Answer 27

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

Question 28

Is phenylephrine or ephedrine preferred for parturient patients?

Answer 28

**Phenylephrine Preferred** * Both are effective but Ephredrine crosses the placental barrier and increases fetal metabolic requirements. Has also been shown to decrease fetal pH, base excess, and umbilical O2 content.

Question 29

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

Answer 29

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

Question 30

How does epinephrine (epi wash), administered neuraxially, affect UBF?

Answer 30

- No change in healthy patients

Question 31

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

Answer 31

10 - 15 mcg (generally doesn't change UBF)

Question 32

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

Answer 32

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

Question 33

Neuraxial anesthesia will increase UBF if _________ is avoided.

Answer 33

hypotension (if HoTN is present, will lead to decreased UBF)

Question 34

How does magnesium sulfate affect UBF?

Answer 34

* Relaxes smooth muscle, and causes vasodilation which increases UBF * If HoTN is present, will lead to decreased UBF

Question 35

How do volatile anesthetics affect UBF?

Answer 35

* ↓ UBF if MAC > 1.5 * Minimal effect on UBF with MAC 0.5 - 1.5

Question 36

The chorionic plate of the placenta faces the _____.

Answer 36

fetus

Question 37

The basal plate of the placenta faces the _______.

Answer 37

mother

Question 38

What are the functions of the placenta?

Answer 38

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

Question 39

What is the intervillous space?

Answer 39

Large placental sinus with multiple folds

Question 40

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

Answer 40

False. The intervillous space is a low resistance area.

Question 41

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

Answer 41

~350mls of maternal blood

Question 42

Where does blood enter into the intervillous space from?

Answer 42

spiral arteries

Question 43

The umbilical vein carries __________ blood.

Answer 43

oxygenated

Question 44

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

Answer 44

deoxygenated