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Flashcards in Exam 2 Fetal Stuff Deck (107)
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1

Blood supply to the placenta is mainly from

Uterine arteries

2

The uterine artery arises bilaterally from the

internal iliac arteries

3

In pregnancy, flow my differ between the R+L uterine arteries- explain

The vessel that supplies the placental side will have 18% increase in blood flow and 11% increase in diameter

4

How much is the uterine blood flow in the non-preg

50-100ml/min

5

How much is the uterine blood flow at term?

700-900ml/min

6

At term, how much uterine blood flow perfuses the placenta and how much perfuses the myometrium?

80% perfuses placenta
20% perfuses the myometrium

7

Maximal dilation of uterine vessels during pregnancy- So what is absent?

autoregulation is absent

8

Extreme hypocapnia does what to the uteroplacental blood flow?

Extreme hypocapnia (PaCo2<20mmHg) causes decreased UBF causing fetal hypoxemia and acidosis

9

UBF is directly proportional to

Uterine perfusion pressure (which is the difference between uterine arterial pressure and uterine venous pressure)

10

How do you calculate uterine perfusion pressure?

U arterial pressure - U venous pressure

11

Uterine perfusion pressure is directly proportional to

Uterine blood flow

12

UBF is inversely proportional to

Uterine Vascular resistance

13

Uterine Vascular resistance is inversely proportional to

UBF

14

How do you calculate UBF?

Uterine perfusion pressure/Uterine Vascular resistance
Or in other words UBF= UAP-UVP/UVR

15

What are the 3 major factors that decrease UBF?

Hypotension (decreases uterine perfusion pressure)
Uterine vasoconstriction (Increases UVR)
Uterine contraction (Dec UPP and Inc UVR)

16

What happens to uterine perfusion during contractions?

Decreases

17

What happens to uterine perfusion during uterine relaxation

Increases

18

What some things that can cause Decreased uterine arterial pressure?

Supine position (aortocaval compression)
Hemorrhage/hypovolemia
Drug-induced hypotension
Hypotension during sympathetic blockade

19

What are some things that can cause Increased uterine Venous pressure?

Vena caval compression
Uterine contractions
Drug induced uterine tachysystole (oxytocin, LA)
Skeletal muscle hypertonus (Scz, Valsalva)

20

What can cause Increased Uterine Vascular Resistance?

Endogenous vasoconstrictors - Catecholamines, Vasopressin
Exogenous Vasoconstrictors- Epi, Neo, ephedrine, LA

21

NA will cause (increased/decreased) uterine blood flow?

Both

22

How does NA increase UBF?

Increase by:
Pain relieve
Decreased sympathetic activity
Decreased maternal hyperventilation

23

How does NA decreased UBF?

Hypotension
Unintentional IV injection of LA or epi
Absorbed local anesthetic (little effect)

24

How do inhalational agents affect UBF?

0.5-1.5 MAC has little to no effect on UBF

25

How does ventilation effect UBF?

Moderate hypoxemia and hypercapnia have little effect
However Alkalosis will decrease UBF. So AVOID HYPERVENTILATION .

26

The maternal side of the placenta is called the

Basal plate or Dicidua Basilus

27

The fetal side of the placenta is called the

Chorion or Chorionic plate

28

What lies between the Basal plate and the Chorionic Plate?

Intervillous space

29

How much blood can be held in the intervillous space?

350ml

30

Where does O2/Nutrient Exchange occur in the placenta?

Terminal Arterioles/terminal villi