Tocolytic Therapy for Acute Preterm Labor: Cook Flashcards
Which racial demographic is 2x as likely to have a preterm birth as white women?
African Americans
What is the leading cause of perinatal morbidity/mortality?
Preterm birth
How do microorganisms in the upper genital tract initiate preterm labor?
Activate immune response—> cytokines and prostaglandins —> uterine contractions and weakening of amniotic membranes
If tocolytics have NOT been shown to decrease the chance of preterm birth, what are they good for?
They have been shown to temporarily inhibit uterine contractions.
What is the primary goal of tocolytics?
::Give time to administer glucocorticoids to reduce the risk of prematurity related complications such as respiratory distress syndrome, necrotizing enterocolitis, and intraventricular hemorrhage.
::Secondarily, allows time to transport mother to a facility capable of providing more advanced neonatal care.
When do you cease tocolytic therapy?
When your primary/secondary goals have been met and the pros of tocolytic tx are outweighed by drug exposure risk. Generally by week 34 of gestation.
The MOA of Mg sulfate as a tocolytic is not completely understood. What DO we know about its action?
Functions at the extracellular and intracellular levels by decreasing the availability of Ca2+ by blocking membrane and intracellular Ca2+ channels, which decreases myometrial contractility.
Is Mg sulfate shown to be more efficacious than other tocolytics, given that it is the most widely used tocolytic even today?
No.
When is Mg sulfate contraindicated?
Renal insufficiency (excreted by kidneys) and myasthenia gravis.
What are the common (up to 60% of pts) side effects of Mg sulfate?
What is the most common first sign of toxicity?
flushing, nausea, blurry vision, h/a, lethargy, HypoT, pulm. edema.
Loss of patellar reflexes is the first sign of toxicity, followed by decr. urine output.
What are some possible risks to the fetus caused by Mg sulfate?
Depressed GI and respiratory function.
So if Mg sulfate is not more efficacious than other tocolytics, why does anyone use it?
Neuroprotective. Reduces risk of cerebral palsy and gross motor deficit by almost 50% in preterm births.
Why were Beta mimetics pulled from the market for use in the US as tocolytics?
Maternal cardiotoxicity and death.
In a word, how do beta mimetics work to reduce uterine contractility?
beta-receptor adrenergic agonists, relaxing smooth muscle, including the myometrium. Binding of the receptor initiates a cascade including adenylyl cyclase and protein kinase. This cascade decreases the availability of intracellular calcium and the activity of myosin light-chain kinases, thus suppressing myometrial contractility.
Which beta mimetic is used in the US most often as a tocolytic, off label?
What are its negative side effects in the mother?
When are beta-mimetics contraindicated?
Terbulaline.
SFX: tachycardia, tremor, dyspnea, chest discomfort, palpitations, hyperglycemia.
Contraindications: known cardiac disease, poorly controlled diabetes, meternal HR > 120bpm, significant symptoms such as chest pain/dyspnea.