The Uterus and Labor Flashcards
What is uterine blood flow (mL/min) in the non-pregnant patient?
100 mL/min
How is uterine blood flow regulated?
It is not autoregulated
Dependent on MAP, cardiac output, and uterine vascular resistance
What is the formula for uterine blood flow?
uterine BF= (U artery pressure - U venous pressure ) / U vascular resistance
What are causes of decreased uterine blood flow?
Decreased perfusion (hypotension, hemorrhage, aortocaval compression)
Increased resistance (uterine contraction, hypertensive conditions)
What does the first stage of labor entail?
Beginning of regular contractions to full cervical dilation (10cm)
What does the second stage of labor entail?
Full cervical dilation to delivery of the fetus
Pain in perineum begins during stage two
What does stage three entail?
Delivery of the placenta
What part of the graph represents the latent phase of labor?
A
What part of the graph represents the active phase of labor?
B
What part of the graph represents the first stage of labor?
The blue and green shaded area
What part of the graph represents the second stage of labor?
The pink shaded area
What part of the graph represents the thirst stage of labor?
The purple shaded areas
What part of the graph represents the thirst stage of labor?
The purple shaded area
What are ASA guidelines regarding NPO status in laboring mothers?
Drink moderate amount of clear liquids throughout labor
Eat solid foods up to the point of neuraxial blockade
How does placing an epidural affect labor progression?
It does not prolong the first stage of labor
It does not increase the need for a cesarean section
To what nerve roots do pain signals travel during the first stage of labor?
T10- L1 posterior nerve roots
To what nerve roots do pain signals travel during the second stage of labor?
S2- S4 posterior nerve roots
What is the afferent pathway of the first stage of labor?
Visceral C fibers of the hypogastric plexus
What regional techniques cover pain felt in the first stage of labor?
Neuraxial (spinal, epidural, CSE)
Paravertebral lumbar sympathetic block
Paracervical block
What is the main risk associated with a paracervical block?
High risk of fetal bradycardia
What is the afferent pathway of the second stage of labor?
Pudendal nerve
What regional techniques address pain associated with the second stage of labor?
Neuraxial (spinal, epidural, CSE)
Pudendal nerve block
How does uncontrolled pain affect the mother and fetus physiologically?
Increased maternal catecholamines > hypertension and reduced uterine blood flow
Maternal hyperventilation > leftward shift of oxyHgb curve > reduced delivery of O2 to the fetus
How can N2O be used as an analgesia during labor?
50% N2O + 50% O2 self- administered via facemask
What are some benefits of N2O as an analgesia for labor?
Not associated with hypoxia, loss of airway reflexes, or unconsciousness
Preserves uterine contractility
Does not cause neonatal depression
What is the benefit of a CSE?
Provides rapid onset of spinal anesthesia and the ability to prolong the duration of anesthesia with an indwelling catheter.
