Uteroplacental Circulation

Question 1

What is the blood supply to the uterus?

Answer 1

Uterine artery

Ovarian artery

Question 2

Where does the uterine artery arise from?

Answer 2

Internal Iliac artery

Question 3

Where does the ovarian artery arise from?

Answer 3

Abdominal aorta below the renal arteries

Question 4

What are the branches of the uterine artery?

Answer 4

Accurate artery _ Radial artery_basilar artery_ spiral arteries ( endometrium)

Question 5

During pregnancy how does the blood supply to uterus differ?

Answer 5

Vessel diameter 11% greater
Uterine blood flow 700-900ml/min at term vs 50-100ml/min non pregnant state.
Blood flow 18% greater to side of placental

Question 6

Still phenomenon with regards to uterine blood flow?

Answer 6

increases in common iliac artery blood
flow during pregnancy were associated with corresponding
increases in uterine artery blood flow but also with decreases
in external iliac artery blood flow. This pattern effectively
constitutes a “steal” phenomenon, in which blood flow in
the pelvis is preferentially redistributed toward the uterus

Question 7

What is the characteristics of uteroplacental blood flow?

Answer 7

widely dilated, low-resistance system with per-
fusion that is largely pressure-dependent.16,17 However, a study
in pregnant rabbits found that uteroplacental blood flow was
relatively constant over a wide range of perfusion pressures.

Question 8

Autoregulation of uteroplacental blood flow

Answer 8

limited
autoregulation means that placental blood flow may dimin-
ish with reductions in maternal blood pressur

Question 9

What is the margin of safety

Answer 9

normal physiologic conditions, uterine blood flow exceeds the minimum
required to satisfy fetal oxygen demand.
the relationship between uterine blood
flow and oxygen transfer appears nonlinear and suggests that uteroplacental blood flow can decrease by as much as 50% for limited periods before fetal oxygen uptake decreases and metabolic acidosis occurs. There is an increase in oxygen extraction with increased A-a gradient.

Question 10

What are the determinants of uterine blood flow during pregnancy?

Answer 10

Uterine blood flow is directly proportional to uterine perfusion pressure and inversely proportional to uterine vascular resistance.

Question 11

What is the mechanism of vascular changes: steroid hormones

Answer 11

Steroid hormones

Reduced response to vasoconstriction

Question 12

What is the mechanism of vascular changes: Vascular Response to vasoconstrictors?

Question 13

What is the mechanism of vascular changes: Vasodilators

Question 14

What is the mechanism of vascular changes:

Question 15

What is the mechanism of vascular changes: shear stress

Question 16

What is the mechanism of vascular changes: venoarterial signaling

Question 17

What are the effects of neuraxial anesthesia on uterine blood flow?

Answer 17

Question 18

What are the effects of neuraxial anesthesia on uterine blood flow: hypotension?

Question 19

What are the effects of neuraxial anesthesia on uterine blood flow: Vasopressors?

Question 20

What are the effects of neuraxial anesthesia on uterine blood flow : local anaesthetic?

Question 21

What are the effects of neuraxial anesthesia on uterine blood flow : Epinephrine and a adrenergic agonists?

Question 22

What are the effects of neuraxial anesthesia on uterine blood flow: opiods?

Answer 22

risk for fetal bradycardia from increase in uterine tone and a resulting decrease in uteroplacental blood flow
associated with hypotension that may potentially decrease uterine blood
flow.

Question 23

What are the effects of general anesthesia on uterine blood flow: iv agents?

Question 24

What are the effects of general anesthesia on uterine blood flow : inhalation agents?

Answer 24

there is little reason to choose one inhalational agent over another on the basis of an agent’s effects on uterine blood flow.
dose-dependent reduction in uterine tone caused by inhalational agents increase uterine blood flow

Question 25

What are the effects of general anesthesia on uterine blood flow : ventilation?

Answer 25

Mechanical ventilation decreases uterine blood flow and together with hypocapnia caused fetal hypoxia and metabolic acidosis

Question 26

Effects of mgso4

Answer 26

Infusion of magnesium caused an increase in uterine blood flow, which was associated with an improvement in red blood cell deformability in women with preeclampsia or fetal growth restriction.

Question 27

Effects of antiHPT

Question 28

Effects of calcium channel blockers

Answer 28

Verapamil 0.2 mg/kg was shown to decrease maternal blood
pressure and uterine blood flow in pregnant sheep.154 Studies
with nifedipine have yielded conflicting results. Some animal
studies have shown that nifedipine decreases uteroplacental
blood flow and worsens the fetal condition, whereas human
studies have shown either no change in uteroplacental
blood flow or vascular resistance or a decrease in vascular
resistance.

Question 29

Effects of vasodilators

Answer 29

• increases in total uterine blood flow
do not necessarily result in enhanced placental perfusion
• Nitroglycerin was shown to relax human uterine arteries in
vitro, decreased uterine resistance indices

Question 30

Effect of ionotrops

Answer 30

Restoration of spontaneous circulation and adequate uterine perfusion pressure is far more important than avoidance of uterine vasoconstriction.
maternal welfare is the overriding priority and standard resuscitation drugs should be administered.
• milrinone and amrinone may increase uterine blood flow, whereas dopamine and epinephrine may diminish

Question 31

Effects of oxygen therapy

Answer 31

administration of supplemental maternal oxygen as part of intrauterine resuscitation for suspected fetal compromise, evidence for the benefit of this practice is unclear.
There are reports that blood flow decreased significantly after inhalation of oxygen 5 L/minand suggested that this might be related to a vasoconstrictive effect of maternal hyperoxia