Tocolytics and Uterotonics Flashcards
What interventions are used to prevent and treatment postpartum hemorrhage?
uterogenics (oxytocin, methylergonovine, prostaglandins, misoprostal
Why are ergot alkaloids (Methergine) not administered IV?
because of their potent vascular effects, profound hypertension, nausea and vomiting, cerebral hemorrhage
What is the dose and route of administration for Methergine?
0.2 mg IM, can be repeated 15-20 minutes, total dose 0.8
What do ergot alkaloids cause besides uterine contraction?
increase in blood pressure, central venous pressure, pulmonary capillary wedge pressure
What can prostaglandins cause besides uterine contraction?
nausea, bronchospasm, increased pulmonary vascular resistance
How is Hemabate administered?
IM or directly into uterine muscle
How is preeclampsia defined?
systolic HTN of 140mmHg or higher or diastolic of 90mmHg or higher after 20weeks gestation with proteinuria
What is the one way to end preeclampsia?
delivery
Risk of postpartum hemorrhage interventions
large bore IV, has volume resuscitation, have fluid warmer available, T&C, CBC, coags
In terms of preeclampsia what can be done to enhance fetal lung maturity if no severe features are occurring?
corticosteroid administration
Magnesium sulfate MOA
alter calcium transport and availability for muscle contraction, competes with calcium reducing myometrial contractility, hyperpolarization leads to inhibition of MLCK activity = relaxation of vascular, bronchial, uterine smooth muscle, vasodilation
Magneisum sulfate Indications
preeclampsia (decreases SVR and BP, anticonvulsant, decreases fibrin deposition improving circulation to visceral organs)
Magnesium sulfate Administration
Loading dose 4-6 grams IV in 50mL over 20-30minutes
Infusion 1-2g/hr, continued thru delivery up to 24 hours post delivery
Therapeutic Magnesium level
4-9 mEq/L (normally 1-3)
Magnesium sulfate Side effects
transient hypotension, sedation, skeletal muscle weakness, CNS depression
Magnesium sulfate overdose
discontinue infusion, secure the airway, IV CaCl, diuresis
What do tocolytics do?
relax the uterine muscle, slow down delivery
What are tocolytics concomitantly administered with?
corticosteroids for lung protection of neonate, prior to 33 weeks gestation, maximum benefit 48 hours
Types of tocolytics
magnesium sulfate, calcium channel blockers, b-adrenergic agonists, nitric oxide donors, cyclooxygenase inhibitors, oxytocin antagonists
neonatal side effects of magnesium sulfate
hypotonia, respiratory depression (RARE)
What can happen when serum magnesium is >12mg/dL
respiratory depression
what can happen when serum magnesium is 25 mg/dL
cardiac arrest
What can happen when serum magnesium is 7-9mg/dL
anticonvulsant
What can happen when serum magnesium is 10-12mg/dL
tendon reflexes abolished
what can happen when serum magnesium 15-20mg/dL
SA and AV blocks, respiratory arrest
What calcium channel blocker do we use as a tocolytic and why?
nifedipine, it can be given PO or sublingually
Mechanism of action of Nifedipine
block influx of Ca2+, block release of Ca2+ from SR, inhibit Ca2+-dependent MLCK mediated phosphorylation
How long can birth be delayed for with use of nifedipine?
2-7 days
Side effects of Nifedipine
hypotension, dyspnea, pulmonary edema, tachycardia, HA
Avoid concomitant use with magnesium sulfate
How do B2 agonists work?
stimulates B2 receptors causing smooth muscle relaxation, inhibit myometrial contractility, increase progesterone production
what does progesterone cause?
histologic changes in myometrial cells that limit the spread of contractile impulses
Which B2 agonist do we use the most?
Terbutaline
What are the hazards of B2 stimulation?
- increased blood sugar and insulin levels in mom
- neonatal hypoglycemia and tachycardia
Side effects in mom and fetus with B2 agonists
vasodilation tachycardia dysrhythmias ischemia hypotension pulmonary edema HA hyperglycemia hypokalemia increased plasmin renin and vasopressin
How long should anesthesia be delayed for with B2 agonist administration if possible?
60 minutes to allow HR to come down
if not possible don’t give drugs to increase HR
How should hypotension be treated with B2 agonist administration?
phenylephrine or ephedrine
Which nitric oxide donor do we administer?
nitroglycerine
How do nitric oxide donors work?
increasing cyclic guanosine monophosphate (cGMP), inactivates MLCK = smooth muscle relaxation
Side effects of nitric oxide donors
HA, hypotension
What does cyclooxygenase do?
converts arachidonic acid to prostaglandin h2 which enhance formation of myometrial gap junctions increasing available Ca2+
How cyclooxygenase inhibitors work?
reduce prostaglandin levels by inhibiting COX enzymes from converting arachidonic acid = decreased uterine contraction
Which nonselective COX inhibitor do we use?
Indomethacin
Which COX-2 selective inhibitor do we use?
Celecoxib
Anesthetic implications of COX inhibitors
platelet inhibition with nonselective COX inhibitors
Which muscle relaxant is preferred for RSI with tocolytics?
Succinylcholine
What do uterotonics do?
cause contraction
What is the leading cause of postpartum hemorrhage?
uterine atony
What intervention should be tried first post delivery for PPH?
fundal massage and then oxytocin
What is oxytocin?
endogenous hormone produced by posterior pituitary gland that lowers the threshold for depolarization of uterine smooth muscle
What synthetic oxytocin do we give?
Pitocin - octapeptide
Pitocin administration
20-40 units/L over 15-20minutes post delivery as soon as cord is cut, also used prophylactically to reduce blood loss, never bolus
Pitocin administration to induce labor
infusions at low controlled rates
Side effects of pitocin
vasodilation or decreased SVR = hypotension and tachycardia
2nd line of treatment for uterine atony
ergot alkaloids
which ergot alkaloid do we use?
Methergine - synthetic, MOA is not clear
Contraindications for ergot alkaloids
preexisting hypertension, PVD, ischemic heart disease
what can we give if methergine is contraindicated or not effective?
prostaglandins (hemabate)
MOA of Hemabate
increases myometrial calcium levels, increases MLCK activity = uterine contraction
Administration of Hemabate
250 mcg IM or directly into myometrium, repeat every 15-30minutes, total dose 2mg
Administration of Misoprostol
800-1000mcg, sublingual or buccal
Use of Carboprost (prostaglandin) can result in __ with women with reactive airway disease
bronchospasm, Va/Q mismatch, hypoxemia
