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
