5b Pregnancy

HTHSCI 2H03

What are the two types of drugs used to manage uterine contractions?

1. Oxytocics: stimulate contraction

2. Tocolytics: inhibit contraction

When are oxytocics vs Tocolytics used?

Oxytocics:

- induce/augment labor

- postpartum hemorrhage

Tocolytics:

- premature labor

- uterine hypertonus (spasms)

What are the two ways to stimulate smooth muscle contraction?

1. Gi protein coupled Rc
2. Gq protein coupled Rc

How do Gi protein couple Rc work to increase SM contraction?

- decreased cAMP

- decreased protein kinase

- decreased phosphorylation of Ca++ sequestering proteins

- increase Ca++

- increased contraction

How do Gq protein receptors work to increase SM contraction?

- increased IP3

- stimulates Ca++ release from sarcoplasmic reticulum

- increased DAG

- moves extracellular Ca++ into cell

- increased Ca++

- increased contraction

What is oxytocin? what does it bind to? what effect does it have?

- endogenous ligand
- binds Gq protein coupled Rc
- increases freq and force of contractions

When is it able to exert a biological effect during pregnancy? Why?

- second half of gestation
- oxytocin Rc do not appear in myometrium until then
- to decrease risk of contraction from normal oxytocin release (joy etc)

What are pitocin and syntocinon?

agonist drugs that mimic oxytocin???

What happens when they are administered via IV? When would you use an IV?

- almost immediate uterine response
- subsides in 1 hour
- induction and augmentation of labor

How is do you use pitocin, syntocinon to augement labor?

- increase dose every 15-60 minutes
- until normal labor pattern is established

When should administration be terminated?

- uterine hypertonus --> contractions are
- less than 2 min apart
- longer than 90 seconds
- fetal or maternal distress

What happens at high doses?

- when all oxytocin Rc are full (overdose)
- affinity for ADH receptors
- antidiuretic effect
- pulmonary edema
- HF
- water intoxication

What happens when they are administered via IM injection? When would you use an IM injection?

- 3-5 min uterine response
- subsides in 2-3 hours
- control of post-partum hemorrhage (PPH)

How do prostaglandin agonist work as oxytocics?

- bind to Gi and Gq prostaglandin Rc
- induce contractions at any time during pregnancy

How does disprostone work as a oxytocic?

- vaginal/cervical gel
- increase oxytocin
- cervical ripening
- initiation of labor

What is important to remember with the administration of disprostone?

- pt should remain lateral/supine position for 30 min
- prevent leakage
- repeated q6 hr

What is misoprostol used for?

- control of PPH
- cervical ripening before abortion
- not standard of practice in Canada --> risk of uterine hypertonus

How does ergot alkaloids work as a oxytocic?

- second line tx of PPH after oxytocin
- binds Gq proteins coupled prostaglandin E1 Rc
- binds alpha??-1 adrenoreceptors
- contraction of SM and bl vessels

What are the two routes of administration of ergot alkaloids? What are the types?

Ergonovine --> IV or IM
Methylergonovine --> PO

What is the preferred route of administration?

- IM injection
- 2-3 min contractions
- lasts 3 hours

Why are ergot alkaloids used not used to induce labour?

risk of uterine hypertonus

What is important to monitor with administration of ergot alkaloids? Why?

- BP
- contraction of bl vessels

What are the effects of uterine hypertonus?

- fetal asphyxiation
- uterine rupture

Clients with a hx of what should be managed with caution when using oxytocics?

- cesarean section
- uterine sx
- uterine hypertonus

What two drugs are only used for PPH/contraindicated in pregnancy?

- misoprostol
- ergot alkaloids

Should you combine oxytocic drugs?

no

A RN reviews a postpartum clients hx. The client is prescribed methylergonovine maleate for the control of PPH. The RN plane to contact the HCP if the client has which of the following conditions?
a) HTN
b) rheumatoid artheritis
c) hx of miscarriage
d) hx of premature delivery

a) HTN

When are tocolytic drugs commonly used?

- uterine hypertonus
- preterm labor (delay delivery by 48 hours)
- cephalic version

What is cephalic version? Why is it not used in Canada?

- breach
- physically moving the fetus outside of the abdomen
- induce labor
- umbilical cord wrapping

How many weeks gestation are tocolytic drugs used to delay labor?

24-34 weeks

What does delaying delivery allow?

- administration of glucocorticoids
- get to hospital w NICU
- delay in cases of acute self-limiting conditions that are unlikely to cause recurrent preterm labor (car accident, sx)

Why administer glucocorticoids?

- increase likelihood pf preterm survival

- increase fetal lung development

- reduces risk of complications

- RDS

- bleeding in the brain

- necrotizing enterocolitis and sepsis

When is glucocorticoids therapy recommended?

- preterm labor (24 - 36 6/7 weeks of gestation)
- high probability pt will deliver in next 7 days

What are the two drugs used in glucocorticoid therapy? What is the dosage?

1. Betamethasone --> two 12mg IM 24 hours apart

2. Dexamethasone --> four 6mg IM 12 hours apart

When should tocolytic drugs be used? (3)

1. 24-34 weeks gestation
2. regular contractions
- longer than 45 seconds
- 2-10 min apart
3. cervix is dilated more than 2cm & begun to efface (thin)

When should you used glucocorticoid therapy but not tocolytic drugs?

34 - 36 6/7 weeks

What is an example of a toclytic prostaglandin inhibitor (NSAID)?

Indomethacin

How does it work as a tocolytic drug?

- inhibits COX1 and COX2 enzymes
- inhibits prostaglandin synthesis
- endo prostaglandins are oxytocics

What is the risk with indomethacin?

PPH

When should indomethacin be used with caution?

- platelet disorders
- renal dysfunction
- NSAID sensitive asthma
- peptic ulcer disease (PUD)

how many weeks does it have increase adverse effects? Why?

- 32 weeks
- premature closure of ductus arteriosus
- pulm HTN
- tricuspid regurgitation
- renal failure

What do you used after 32 weeks then?

- Ca++ channel antagonist
- Nifedipine

How does Nifedipine work as a tocolytic drug?

- inhibits entry of extracellular Ca++ into myometrial cells
- slows uterine contractions

What are some risks with Nifedipine?

- H/a
- dizziness
- reflex tachycardia
- due to hypotension

When can nifedipine also be used? but what is the preferred drug?

- severe gestational HTN
- preferred tx --> labetalol

what is magnesium sulphate a good choice and poor choice for?

good choice for --> eclampsia, fetal neuroprotection in preterm birth
poor choice for --> tocolysis

Why are beta 2 adrenergic agonists (terbutaline) poor tocolytics?

- rapid reduction in efficacy
- adverse effects
- tachycardia
- tremor
- palpitations

What drug is not available or used in north america?

Oxytocin Rc antagonists (atisoban)

Your pt is recovering form a c section. During post partum assessment, you note a flaccid uterus and increased vaginal bleeding. the HCP orders you to prepare to administer...
a) misoprostol, a prostaglandin agonist
b) Pitocin, a oxytocin rc agonist
c) Nifedipine, a Ca++ channel antagonist
d) Ritodrine, a beta-2 rc adrenergic receptor agonist

b) Pitocin, a oxytocin rc agonist

What is the first line tx for tocolysis in cases of preterm labor between 24-32 weeks?

Indomethacin

What is the first lien tx for tocolysis in cases of preterm labor between 32-43 weeks?

Nifedipine