Exam 11: Oxytocics Flashcards Preview

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Flashcards in Exam 11: Oxytocics Deck (43):
1

What hormone ratio is important in promoting parturition?

Increased estrogen to progesterone

2

What hormone prevents contractions throughout pregnancy?

Progesterone

3

Two mechanisms behind progesterone preventing uterine contractions

1. Hyperpolarizing membrane potential of smooth muscle cells
2. Promoting Ca2+ storage in the sarcoplasmic reticulum

4

3 mechanisms behind estrogen promoting contractions

1. Induction of Na+ channels
2. Induction of gap junctions
3. Induction of oxytocin receptors

5

What causes softening/ripening of the cervix for parturition?

Prostaglandins

6

3 uses for Oxytocics

1. Induction or augmentation of labor
2. Control of postpartum uterine hemorrhage (the number 1 cause of maternal mortality)
3. Induction of abortion or expulsion of dead fetus after intrauterine death

7

2 uses of Tocolytics

1. Delay or prevention of preterm labor
2. Slow or arrest delivery so therapeutic actions can be taken

8

Definition of pre-term labor

Before 37 weeks
Contractions every 10 minutes lasting 30 seconds

9

Chemical composition of Oxytocin

Nonapeptide (9 amino acids)

10

Oxytocin mechanism

Gq (increased calcium, phospholipase C)

11

What causes increased sensitivity of the uterus to oxytocin in gestation?

Estrogen

12

Goal of IV oxytocin in labor induction

3-5 contractions of 60-90 seconds per 10 minute period without fetal distress

13

Most common indication for Oxytocin use in labor induction

Prolonged pregnancy (42 weeks)

14

4 reasons for oxytocin labor induction

1. Mother or fetus is at risk and you need to deliver now
2. Premature rupture of membranes
3. Prolonged pregnancy
4. Selective induction (mom's choice)

15

Oxytocin effects on breast

Contracts myoepithelial cells forcing milk out of the alveoli of the breast

16

CV side effects of Oxytocin

Hypotension
tachycardia
arrhythmia

17

Electrolyte abnormality associated with Oxytocin use

Hyponatremia due to antidiuretic effect and water retention
Can lead to seizures and death

18

Serious fetal complication associated with oxytocin use

Sustained contraction/hyperstimulation can interfere with fetal circulation

19

Oxytocin contraindications (3)

1. Abnormal fetal position
2. Fetal distress
3. Previous uterine surgery

20

What happens to prostaglandin production in pregnancy?

Increases in the 3rd trimester from the placenta and endometrium

21

PG effect on the uterus (mechanism)

Cause contractions by mediating an increase in intracellular calcium

22

PG effects on cervix (mechanism)

Cervical ripening by increasing secretion of collagenase

23

Dinoprostone

PGE2

24

Prepidil, Cervidil

PGE2 preparations used for cervical ripening

25

2 side effects of PGE2 preparations (prepidil, cervidil)

1. GI disturbance
2. Uterine hyperstimulation

26

PGE2 contraindications

Same as oxytocin
1. Abnormal fetal position
2. Fetal distress
3. Previous uterine surgery

27

15-methyl PGF2alpha (Carbaprost) Tromethamine
(2 uses)

2nd line drug to control postpartum bleeding after oxytocin or ergot alkaloids
Can also induce abortion in the second trimester

28

Misoprostol

PGE1 analog
Used to terminate early pregnancies (up to 49 days from LMP)
Promotes uterine contractions and causes detatchment

29

Ergonovine and Methylergonovine

Ergot Alkaloids
Binds alpha-1 receptors, causing an increase in Ca2+ and uterine contractions
Used for postpartum or post abortion bleeding

30

Ergonovine and Methylergonovine uses

Postpartum or post abortion bleeding
DO NOT use for labor induction or augmentation

31

Ergot alkaloid side effects

Think alpha 1
HTN due to vasoconstriction
NVD
Gangrene of the fingers/toes

32

Ergot alkaloid contraindications

HTN
CV disease
Liver or kidney disease

33

Mifepristone

Progesterone antagonist

34

Mifepristone use, mechanism

Termination of pregnancy up to 49 days from LMP
Progesterone antagonist
Causes detachment of the products of conception

35

Sodium Chloride 20%, urea 40 50% injection mechanism

Damages mucosa of uterus causing release of Prostaglandins leading to uterine contractions

36

Sodium Chloride 20%, urea 40 50% injection use

late term abortions

37

FDA approved tocolytic agent

There isn't one

38

When are tocolytics used/

to delay premature labor up to 24 hours in patients between 24 and 34 weeks gestation

39

Indomethacin

PG-synthetase inhibitor
use to prevent labor at weeks 24-32.
Dont use it after 32 weeks or you may cause closure of ductus arteriosus and oligohydramnios

40

nifedipine mechansim

inhibits contractions by decreasing intracellular calcium

41

Nifedipine use in pregnancy

used as a tocolytic between 32-34 weeks because you wouldn't want to use indomethacin that late

42

Terbutaline

B2 agonist
Inhibits contraction
Very dangerous to mother and fetus
Difficult to dose correctly

43

Mg sulfate

Tocolytic
decreases intracellular calcium
Not very effective at delaying birth