Chapter 52: Pregnancy & Preterm Labor Drug Therapy

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Welcome back to the Deep Dive.

Today we are wading into what I would argue is the single most high stakes environment in modern pharmacology.

I think you're right.

We aren't just managing a disease process.

We're managing a biological negotiation between two distinct, sometimes competing systems.

We're talking about the mother and the fetus.

That is the perfect way to frame it.

It is a biological negotiation and sometimes, yeah, a bit of a tightrope walk.

We are doing a deep dive specifically into drug therapy during pregnancy and preterm labor.

And to guide us, we are doing a comprehensive step -by -step care down of chapter 52 from

a patient -centered nursing process approach, the 12th edition.

Now, I know our listeners.

We have a lot of nursing students, new clinicians, people who listen to this to get the edge.

So what's the mission today?

The mission is to move beyond the flashcards.

I mean, anyone can memorize a dose.

We want to understand the why.

Why does a pregnant body metabolize drugs differently?

Why do we use, you know, a central nervous system depressant to treat high blood pressure complications?

We are going to systemize the chaos of maternal fetal pharmacology.

We are going to walk through this chapter exactly as it's laid out.

So if you have your book, you can actually follow right along with us.

And we're talking about a chapter that is, let's be honest, notorious for being dense.

Oh, yeah.

You've got calculations, black box warnings, physiological contradictions.

It can be intimidating.

It is dense, but it's logical.

It really is.

If you understand the physiology, the pharmacology follows naturally.

So here's our roadmap for this session.

We're going to start with what the book calls the pharmacokinetic shift, how the pregnant body handles drugs.

OK.

Then we move to the maintenance phase, therapeutic drugs like iron and vitamins.

After that, we'll get into the weeds of managing those minor discomforts.

Which are never minor.

Never minor, no.

And then we'll finish with the real critical care scenarios,

preterm labor and preeclampsia.

Let's start right at the beginning of the chapter with that pharmacokinetic shift.

I think the layperson assumes that a pregnant woman is just a normal woman with a bump.

But the source material suggests that biochemically, she's almost a different species.

She effectively is.

I mean, it's a profound change.

When we talk about pharmacokinetics, we're talking about those four phases, absorption,

distribution, metabolism, and excretion.

In pregnancy, every single one of those phases is altered.

Every single one.

Everyone.

Let's look at absorption first.

It's not business as usual in the GI tract.

Right, because you have these massive surges in hormones, specifically progesterone.

And progesterone is the relaxing hormone, where it just kind of chills everything out.

Correct.

It relaxes smooth muscle.

But that doesn't just mean the uterus.

It includes the entire gastrointestinal tract.

So you have reduced gastrointestinal motility, the stomach empties slower, the intestines move slower.

Okay, so let's play that out.

If I take a pill, it's sitting in my stomach longer.

Does that mean it absorbs better because it's there longer or worse?

What happens?

It's a bit of a double -edged sword that the text highlights.

Because the transit time is slower, some drugs might actually absorb more completely.

They just have more contact time with the absorptive surfaces.

Okay, that makes sense.

But the flip side is, the onset of action is often delayed.

So if you need a drug to work fast, pregnancy physiology is, well, it's working against you.

And the text also mentions pH changes in the stomach.

That's another factor.

A huge factor.

The stomach becomes less acidic during pregnancy.

The gastric pH actually rises.

Which matters for how drugs break down.

Hugely.

Some drugs require a highly acidic environment to dissolve properly before they can even be absorbed.

If the pH is higher, they just don't break down as efficiently.

So you've got slow movement plus a different chemical environment.

What a tough combination.

And that's just the gut.

The even bigger change regarding absorption happens in the lungs.

The text mentions tidal volume.

What is that exactly?

Tidal volume is the amount of air you move with each normal breath.

And in pregnancy, that increases by 30 to 40 percent.

A pregnant woman is moving a lot more air to oxygenate herself and the fetus.

So inhaled drugs,

like for asthma.

They absorb much, much faster and more efficiently.

A pregnant patient with asthma using an inhaler might get a stronger systemic hit from that same puff than she did before she was pregnant.

It's something the nurse has to be really aware of.

Okay, so the drug is in the body.

Now it has to go somewhere.

This is distribution.

And this is where that concept of dilution comes into play.

This is a massive factor.

During pregnancy, maternal blood volume expands significantly.

We're talking up to 50 percent above baseline.

50 percent.

Wow.

And the plasma volume, the liquid part, increases even faster than red blood cell production.

So let's use an analogy.

If you have a standard dose of a drug, say, a teaspoon of red dye and you dump it into a bucket of water, it's a certain color.

If you dump that same teaspoon into a bathtub.

It's much lighter.

That is exactly what happens.

The expanded blood volume leads to drug dilution.

So you get a lower plasma drug concentration for the very same dose.

But wait, there's a twist with proteins, right?

It's never that simple.

There is always a twist in pharmacology.

So many drugs travel through the blood bound to proteins, specifically albumin.

Think of albumin as a taxicab.

Okay.

If the drug is in the cab, it's inactive.

It can't do anything.

It has to get out of the cabby free drug to actually work at the receptor site.

And in pregnancy, what happens to the taxicabs?

The concentration of those proteins of albumin decreases.

There are fewer taxicabs available.

Which means you have more free drug just circulating around looking for a receptor.

Exactly.

And only the free drug is active.

So you have this kind of push -cull dynamic.

The extra blood volume is diluting the drug, which lowers the concentration, but the lack of proteins might actually raise the active amount of free drug.

That sounds like a dosing nightmare for the prescriber.

It is complex.

And then to make it even more interesting, you have to factor in excretion, the kidneys.

I remember reading about GFR, the glomerular filtration rate.

Right.

Renal blood flow effectively doubles.

The kidneys are just working overtime.

The glomerular filtration rate increases by about 50%.

So the kidneys are flushing the blood much, much faster than in a non -pregnant patient.

So drugs that are excreted by the kidneys, like, say, lithium or even some simple antibiotics.

They get washed out of the system incredibly fast.

The half -life shortens.

The drug enters the body, gets diluted, and then gets flushed out the exit door at high speed.

Okay.

So here is the clinical question that I think every student listening right now is asking themselves.

We have dilution.

We have rapid excretion.

My gut instinct says, she's pregnant.

Let's be safe.

Let's give her a lower dose to avoid hurting the baby.

But the text explicitly flags this as a really dangerous assumption.

It is a critical error.

And the authors of Chapter 52 are very, very specific about this.

If you lower the dose and extend the interval so you give the drug less often while her body is actively diluting it and excreting it faster, you're absolutely going to reach subtherapeutic levels.

Meaning the drug effectively just stops working.

You're not actually treating the condition.

Exactly.

You aren't treating the infection.

You're not treating the hypertension or the epilepsy.

And we have to remember,

an untreated illness in the mother is often far more dangerous to the fetus than the drug itself.

That's a huge point.

If mom has an uncontrolled seizure, the fetus loses oxygen.

If mom has an uncontrolled infection, the fetus is at risk.

So the clinical implication here is huge.

Do not underdose just because of pregnancy.

You have to treat the pathology.

You have to treat the mother to protect the baby, which brings us to the gatekeeper, the placenta.

You know, I really dislike the word barrier when we talk about the placenta.

And the text tries to correct this misconception.

It is not a wall.

It is a sieve.

It is an organ of exchange.

So clinically, should the nurse just assume everything gets through?

Is that the safest bet?

Safest bet, yes.

Assume most things get through to some degree.

However, the text details the specific variables that determine how much of a drug gets through.

Okay, let's break those down.

First, molecular weight.

It's simple physics.

Small molecules cross easily.

Most drugs are, relatively speaking, small molecules.

Okay.

Second, ionization.

Electrically charged molecules' ions have a much harder time crossing the

And third is lipid solubility.

If a drug dissolves easily in fat, it crosses the placenta much more easily than something that's water soluble.

But the text mentions a metabolic function of the placenta, too.

So it's not just a passive filter.

It's actually doing something.

That's a key point.

The placenta is an active organ.

It has its own enzymes.

It can metabolize some drugs, breaking them down before they even reach the fetus.

It tries to protect the baby.

It's like a first line of defense.

It is.

But here is the scary part, where the nurse needs to be really alert.

The fetal liver.

It's kidney, obviously.

Immature.

It's not just the size.

It's the maturity.

The fetal liver is very immature.

It lacks the full suite of enzymes to break down drugs effectively.

So even if the drug gets to the fetus, the baby can't really handle it.

The baby can't metabolize it.

So a dose that the mother's adult liver clears from her system in four hours might linger in the fetus for 12 hours or even more.

The drug effects are prolonged and can be much more intense.

That is why we are so incredibly cautious.

The baby is literally holding on to the medication.

That is a really sobering thought.

OK, let's pivot to section two.

We've talked about the challenges.

Let's talk about the things we actually want the mother to take.

The therapeutic drugs, specifically iron.

The text used this phrase,

iron cost.

It sounds like a tax.

It is a physiological tax.

Pregnancy is expensive for the body's resources.

The text breaks down the math.

You need iron for the growing fetus.

You need iron for the placenta and you need a ton of iron to build all that extra blood volume we just talked about.

So what's the total bill?

What's the cost?

The total iron cost is about 600 to 800 milligrams over the course of the entire pregnancy.

And a normal diet gives you what, a fraction of that?

Nowhere near that.

The standard recommended daily allowance, the RDA, for a non -pregnant woman is about 18 milligrams.

But in pregnancy, specifically to prevent maternal anemia, we supplement 60 to 120 milligrams of elemental iron daily.

That is a massive dose increase.

And anyone who has ever had to take an iron supplement knows it is rough on the gut.

Oh, it is notorious for GI side effects.

Nausea, vomiting,

really severe constipation, abdominal cramping, and of course the classic black tarry stool.

Which in any other context looks exactly like a GI bleed.

It does.

It looks like melena.

If you do not warn the patient about this, they will panic.

They'll call the office thinking they are bleeding internally.

The nurse has to say, this is normal.

It's expected.

It means you're taking your meds and your body is processing the iron.

So let's talk about absorption hacks.

I'm a nursing student.

I'm getting ready for an exam or I'm advising a patient.

What do I absolutely need to know about administering iron to make sure it actually works?

Acid helps.

Remember we just said the stomach is less acidic in pregnancy.

That hurts iron absorption.

So we have to help it along.

The standard recommendation is to take iron with water or even better juice on an empty stomach.

And specifically vitamin C helps, right?

Remember that from somewhere.

Yes.

Vitamin C creates a more acidic environment in the stomach that dramatically enhances iron absorption.

So orange juice is the gold standard recommendation.

Take your pill with a small glass of OJ.

Okay, so that's what helps.

What hurts absorption?

What are the big inhibitors to watch out for?

Calcium is the biggest one.

Calcium binds to the iron and prevents it from being absorbed.

So no milk, no cheese, no yogurt, no tums at the pill.

What about breakfast drinks?

Coffee?

Tea?

Nope.

They contain compounds called tannins, which also block absorption and absolutely no eggs with your iron pill.

Eggs.

Why eggs?

Eggs contain a protein called phosphatine, which binds iron in the gut.

So that classic breakfast of eggs, toast, coffee, and an iron pill is basically useless from an iron standpoint.

The iron won't get absorbed.

And antacids I'm guessing are a no go as well.

Right, because antacids neutralize the stomach acid we need for absorption.

You have to separate them by at least two to four hours.

So the takeaway for the patient is pretty clear.

Take it with orange juice, not your morning latte, and keep it far away from your tums or your glass of milk.

Precisely.

And one more mechanical tip.

If it's liquid iron, which some people take if they can't swallow pills, you have to use a straw.

Because it stains the teeth.

It will turn teeth a dark gray or even black.

It stains the enamel permanently.

You want to bypass the teeth entirely and aim for the back of the throat.

Okay, moving to the other big supplement,

folic acid.

This is primarily about preventing neural tube defects.

But the timing is the really tricky part here, isn't it?

It is the tragedy of timing in obstetrics, really.

The neural tube, which is the structure that folds over to become the baby's brain and spinal cord, closes very, very early in pregnancy.

We're talking within the first 28 days.

Which is often before a woman even realizes she's pregnant.

Exactly.

By the time she misses a period, takes a test, gets a positive result, the tube is already closed.

If she didn't have enough folate on board during those first four critical weeks, the damaged spina bifida and encephaly, it's already done.

So the strategy isn't just to treat pregnant women.

It's broader than that.

No.

The strategy has to be to treat all women of childbearing potential.

The U .S.

Preventive Services Task Force recommends 400 micrograms daily for any woman who might become pregnant.

It's a preventive strike.

And then if you are actively pregnant, the dose goes up.

Yes, it goes up to 600 micrograms to support all the rapid cell division and fetal growth.

And here is a critical variation that you'll see on exams.

If a woman has a history of a previous pregnancy with a neural tube defect, the dose skyrockets.

How high are we talking?

4 ,000 micrograms.

That is 10 times the standard dose.

It's a massive protective dose to try to prevent recurrence.

Are there any real side effects to folic acid?

It seems pretty benign.

Very few.

It's water soluble, so you excrete what you don't need.

But the text does note it can turn urine an intensely yellow color.

It's just another one of those things to warn the patient about so they don't worry if something is wrong with their kidneys.

Okay, so iron and folic acid are the big dos.

Let's talk about the don'ts.

Specifically, herbs.

There's this pervasive and dangerous myth that natural equals safe.

That is the naturalistic fallacy.

And in pregnancy, it is incredibly dangerous.

The text is very clear.

Many, many herbs are unsafe.

Nurses need to ask specifically about herbal use because patients often don't think to list them as medications on their intake forms.

So run us through the hit list that's provided in chapter 52.

What are the big ones to avoid?

Let's start with some common cooking herbs that are dangerous and concentrated supplement form.

Feverfew, sage, and rosemary.

Wait, rosemary.

Like on chicken.

That's not safe.

In culinary amounts, you know, sprinkling it on your chicken is fine, but taking a concentrated rosemary supplement or oil, absolutely not.

They are what we call eminogogs.

And what does that mean?

It means they stimulate blood flow to the uterus.

They can actually provoke menstruation.

In pregnancy, the last thing you want to do is stimulate uterine bleeding.

Got it.

Okay.

What else is on the list?

It can decrease platelets.

And you need your platelets for clotting, especially during birth.

Then you have the herbs that increase bleeding risk.

Don Quai, high dose garlic, and ginkgo.

If a patient is taking high doses of garlic or ginkgo, she is at a much higher risk for hemorrhage during delivery.

What about St.

John's wort?

People take that for depression.

The text specifically warns that it has shown mutagenic effects in studies.

It can potentially damage fetal DNA.

So avoid it.

And then there are the ones that are even more dangerous.

Yes.

Then you have the straight up abortifacients herbs that can actually trigger miscarriage or abortion.

Pennyroyal, rue, and blue cohosh.

These act directly on uterine muscle to force a contraction.

It really emphasizes that the nurse has to be a detective.

You have to ask, are you taking any teas, any roots, any vitamins that aren't your prenatal vitamin?

Correct.

If you don't ask the right way, they won't tell you because they just assume it's tea and it's harmless.

Let's move into section three, drugs for minor discomforts, which having seen friends go through pregnancy is a terrible name.

These minor discomforts can be absolutely debilitating.

They can be.

They really can.

Let's start with the classic nausea and vomiting morning sickness, which as we know often lasts all day.

The text suggests starting with non -pharmacologic interventions first, right?

Always.

You always start there.

Crackers at the bedside to eat before getting up.

Eating small frequent meals so the stomach is never totally empty or totally full.

And separating fluids from solids.

What does that mean separating fluids from solids?

It means don't drink a huge glass of water with your dinner.

Drink it between meals.

It just stops the stomach from getting over distended, which can trigger nausea.

But when that inevitably fails for some people.

Then we can look at the FDA approved pharmacological treatment.

It is a combination product.

Paradoxin hydrochloride and doxylamine succinate.

Let's unpack those.

Paradoxin is just vitamin B6.

Correct.

And doxylamine is an antihistamine.

It's actually the same active ingredient you find in some over -the -counter sleep aids.

Like unisum.

So how does an antihistamine help with nausea?

It's thought to work by blocking the H1 receptor.

It seems to reduce the vomiting signal in the vestibular system of the brain.

But because it's an antihistamine that crosses the blood -brain barrier, what is the major side effect going to be?

Drowsiness.

Sleepiness.

Somnolence.

Significant CNS depression.

So the patient needs to know she might be very drowsy.

She shouldn't be driving or operating machinery until she knows how it affects her.

What about some of the stronger stuff?

I've heard of Zofran or Ondansetron being used pretty frequently.

It is used, but the text is careful to note that Ondansetron is usually reserved for hyperemesis gravidarum.

That's the severe, can't keep anything down, hospitalization level vomiting where the patient is getting dehydrated and losing weight.

And why is it reserved?

The reason it's reserved is that the fetal safety data is a bit conflicting.

Some studies have suggested a very small increased risk of things like cleft palate or heart defects.

So it's not our first swing at the ball.

We use it when the benefits of stopping the vomiting outweigh those potential risks.

And Promethazine or Promethazine is another option, but it carries a very severe black box warning.

It can cause severe tissue injury, including gangrene, if it's injected incorrectly.

Gangrene from an anti -nausea med.

Yes.

If it leaks out of the vein into the surrounding tissue, what we call extravasation, it is incredibly caustic and kills the tissue.

It can lead to amputation.

So extreme caution is needed with IV Promethazine.

Yikes.

Okay.

Next, discomfort,

heartburn,

pyrosis.

Why is it so awful in pregnancy?

It's a perfect storm of mechanics and chemistry.

Mechanically, the growing baby is pushing the stomach up.

Chemically, progesterone relaxes the cardiac sphincter.

That's the little valve at the top of the stomach that keeps acid down.

So you've got a loose valve and high pressure from below.

Acid flows right up into the esophagus.

And antacids are the go -to are preferred.

But there are important safety alerts here.

You can't just use any antacid.

You have to avoid baking soda.

Why?

My grandmother swears by baking soda and water for her heartburn.

Baking soda is sodium bicarbonate, has a very high sodium load.

In a pregnant woman who is already prone to fluid retention and edema, dumping that much sodium into her system can cause serious electrolyte imbalances and make her swelling much worse.

And what about just pure magnesium -based antacids?

You have to be careful with long -term high dose use, especially in the last trimester.

The text warns it can cross the placenta and potentially cause fetal renal issues and muscle problems.

And bringing a full circle back to our earlier point, don't take the antacid with your iron pill.

Correct.

They cancel each other out.

You have to separate those doses by at least one to two hours.

Okay.

Third discomfort, constipation.

We know the iron supplements cause it and we know progesterone slows down the whole gut.

Right.

It's a common complaint.

First line is always going to be bulk forming agents.

That's fiber, like metamucil or psyllium,

and drinking lots and lots of water.

If that fails, we can use docu -seed sodium, which is a stool softener.

It just pulls water into the stool to make it easier to pass.

What should be avoided?

What are the dangerous ones?

Castor oil.

Definitely avoid castor oil.

Why is that?

Castor oil is a very potent stimulant laxative, but it also stimulates uterine contractions.

You do not want to accidentally kickstart labor while you're just trying to cure constipation.

Good to know.

And what about mineral oil?

Also avoid.

Mineral oil works by coating the intestine.

The problem is it blocks the absorption of fat soluble vitamins, specifically vitamin K.

And vitamin K is crucial for blood clotting.

Exactly.

If the mother becomes deficient in vitamin K, the newborn can be born with something called hypoprothrombinemia, which is basically a risk of neonatal hemorrhage, bleeding in the newborn.

That is a massive risk to take for a simple laxative.

Finally, for this section, pain relief, headache, backache, it's constant.

What can she safely take?

Acetaminophen, or Tylenol, is the standard.

It's the most common non -prescription drug used in pregnancy.

It is generally considered safe in therapeutic doses for short -term use.

What about aspirin or ibuprofen and asides?

Generally, they are contraindicated.

Aspirin inhibits platelet aggregation.

It thins the blood, so it increases the risk of bleeding at delivery for both mom and baby.

And ibuprofen is an even bigger problem, especially later on.

Strictly contraindicated in the third trimester.

This is a crucial piece of physiology to understand.

And asides work by blocking prostaglandins, but in the fetus, prostaglandins are responsible for keeping a blood vessel called the ductus arteriosus open.

Remind us what the ductus arteriosus does.

It is a critical blood vessel that connects the pulmonary artery to the aorta in the fetus, and it allows blood to bypass the lungs because the fetus isn't using its lungs to breathe air yet.

It needs to stay open until the moment the baby takes its first breath.

And if you take ibuprofen?

You block the prostaglandins, and that ductus arteriosus can close prematurely while the baby is still in utero.

This causes severe pulmonary hypertension in the fetus and can be fatal.

So no Advil, no Motrin, no Alev in the third trimester, period.

Okay, let's shift gears.

We're moving from uncomfortable to actually dangerous.

Section four, drugs decreasing uterine muscle contractility.

We're talking about preterm labor.

This is where the intensity definitely ramps up.

Preterm labor, or PTL, is defined as cervical changes and uterine contractions that are occurring between 20 and 37 weeks gestation.

And we try to stop it using a class of drugs called tocolytics.

Tocolytic literally comes from the Greek for childbirth dissolution.

We're trying to dissolve the labor.

But here is the reality check the text gives us.

We are using these drugs off -label.

There are no FDA approved drugs specifically for this indication, and we have very strict rules on when we should not try to stop labor.

Like when?

When is it more dangerous to stop it?

If the pregnancy is less than 20 weeks, it's considered non -viable.

If there is fetal demise, if the baby has unfortunately already died, if there is a severe maternal hemorrhage, or if there is coriamnionitis, which is an infection of the amniotic sac and fluid.

In those cases, the uterus is a hostile environment.

Stopping labor is more dangerous than delivering.

But if we are trying to stop it, the goal usually isn't to stop it forever.

It's to buy time, right?

Exactly.

We are trying to buy 48 hours.

Why specifically 48 hours?

What's the magic in that number?

To allow for steroid administration to mature the baby's lungs.

That is the golden window.

We're trying to get those steroids on board to give the baby the best possible chance.

Okay, so let's talk about the drugs we use to buy that time.

First up in the book is Turbutylene.

Turbutylene is a beta -sympathomimetic drug.

So you need to think back to your sympathetic nervous system fight or flight.

It specifically stimulates beta -2 receptors.

And where are the

bronchodilation and in the smooth muscle of the uterus where they cause relaxation.

So we give it to relax the uterus and stop contractions.

But beta receptors are also in the heart.

Beta -1 receptors.

Precisely.

And that's the problem.

It doesn't just relax the uterus.

It hits the maternal heart hard.

It also stimulates those beta -1 receptors in the heart and it causes significant tachycardia.

And there is a black box warning on this one, isn't there?

A very significant one.

It is not for prolonged use, meaning usually no more than 48 to 72 hours.

The risk is severe maternal cardiac problems like arrhythmias and even death.

So as a nurse, if I'm giving my patient Turbutylene, what am I watching for like a hawk?

You are watching the maternal pulse.

If it goes over 120 beats per minute, you hold the dose and call the provider.

You are also watching for any signs of pulmonary edema, shortness of breath, crackles in the lungs.

And any metabolic changes.

Yes, hyperglycemia.

It raises blood sugar.

And because it crosses the placenta, it causes fetal tachycardia and then after birth, neonatal hypoglycemia.

Can you explain that neonatal hypoglycemia part again?

How does that happen?

So the mom has high blood sugar from the drug.

The baby is getting that high sugar supply through the placenta.

So the baby's pancreas makes extra insulin to handle it.

Then the baby is born.

The sugar supply from mom is suddenly cut off, but the baby still has all high insulin circulating in its system.

The baby's blood sugar crashes.

So the nursery team needs to be ready for a hypoglycemic baby if the mom was on Turbutylene.

Exactly.

Communication is key.

The other drug mentioned for PTL is magnesium sulfate.

Now I know we see this mostly for preeclampsia, but it's used here as a tocolytic too.

It is.

The mechanism is that it acts as a calcium antagonist.

It competes with calcium at the cellular level and that relaxes smooth muscle, including the uterus.

But it is a powerful central nervous system depressant.

We will get deep into the safety checks for magnesium sulfate in the preeclampsia section, but just briefly regarding safety here, it's excreted by the kidneys, right?

So that's a big concern.

A huge concern.

So if the patient has any kind of renal impairment, you have to be incredibly careful with the dose because it will build up to toxic levels very, very quickly.

Okay.

So we've used our tocolytics.

We bought our 48 hours.

Now we use that precious time for section five, corticosteroid therapy.

This is the game changer for premature babies.

This is one of the biggest advances in neonatology.

The goal is to accelerate fetal lung maturation.

Specifically, we want to stimulate the production of surfactant.

And surfactant is the stuff that keeps the little air sacs in the lungs from collapsing on themselves, right?

Correct.

Imagine the alveoli, the little air sacs as millions of tiny wet balloons.

Without surfactant, the surface tension is very high and the wet walls stick together.

They collapse with every breath out.

Surfactant reduces that tension so they can stay open and inflate easily.

Without it, the baby develops respiratory distress syndrome or RDS.

And this therapy is most effective when it's given.

When?

The sweet spot is between 24 and 34 weeks gestation.

And the drugs are betamethasone or dexamethasone.

They're both corticosteroids.

Right.

Both are used.

The text notes that betamethasone is often preferred because some studies have shown a decreased risk of a specific type of brain injury in the infancystic paraventricular leukomalacia compared to dexamethasone.

The dosing is very specific.

It is.

For betamethasone, it's 12 milligrams IM, so an intramuscular injection, every 24 hours for just two doses.

That's it.

It takes about 24 hours to start working and the benefits last for about a week.

The text has a big bold safety alert here regarding names.

Yes.

This is a classic pharmacy error trap, a look -alike, sound -alike issue.

You cannot confuse dexamethasone, the lung steroid, with deoxymethasone.

Deoxymethasone sounds almost identical.

What is that?

It does, but deoxymethasone is a topical anti -inflammatory cream.

It's for skin rashes.

It will do absolutely nothing for the baby's lungs.

You have to read the label very, very carefully.

And what are the adverse reactions for the mom from the steroids?

Maternal hyperglycemia again.

Steroids raise blood sugar, so if your patient is diabetic, her sugars are going to go haywire and will need close monitoring.

And there's also a risk of pulmonary edema, especially if you are using it at the same time as a beta -mimetic like tributylene.

You are hitting the system with two different drugs that both cause fluid retention.

Okay.

Let's move to section six.

This is a massive topic.

Gestational hypertension and preeclampsia.

This is the most common serious complication of pregnancy and it's a huge focus for nursing care.

We need to get the definitions straight first because they have evolved over the years.

Okay.

Start with the most basic one.

Gestational hypertension.

That is simply an elevated blood pressure systolic over 140 or diastolic over 90.

That's recorded for the first time after 20 weeks gestation, but without any proteinuria, just high blood pressure.

And preeclampsia.

How's that different?

Historically, the definition was hypertension with proteinuria.

But as of 2013, the American College of Obstetricians and Gynecologists updated this.

Now, you do not need proteinuria for the diagnosis if there are other signs of stomach stress and end organ damage.

Like what?

What other signs?

Things like low platelets, which is thrombocytopenia, impaired liver function, so you'd see elevated liver enzymes,

new onset renal insufficiency, pulmonary edema,

or new onset headaches or visual disturbances.

It's a multi -system disease caused by vasospasms everywhere.

And then what is eclampsia?

That is when the disease process progresses to affect the brain.

Eclampsia is the onset of seizure activity or coma in a woman who has preeclampsia.

What about HELLP syndrome?

That's an acronym for a particularly severe variant of preeclampsia.

H stands for hemolysis, which is the breaking down of red blood cells.

EL is for elevated liver enzymes, and LP is for low platelets.

It's a life -threatening, bleeding and clotting nightmare.

The text says something very profound here.

What is the actual cure for preeclampsia?

The only true cure is delivery of the infant and, just as importantly, the placenta.

Preeclampsia is a disease that is caused by the placenta.

As long as that placenta is in the body, the disease process continues and can worsen.

So everything else, all of the drugs we were about to discuss, is really just a bridge to a safe delivery.

Exactly.

We are managing the symptoms to try and prevent the mother from having a stroke or a seizure while we induce her labor or prepare for a C -section.

Okay, so let's talk about those management drugs.

First, managing the blood pressure itself,

the antihypertensives.

For mild preeclampsia or chronic hypertension in pregnancy, methyl dopa is often the first -line therapy.

It acts centrally in the brain, stimulating alpha -edrenergic receptors to lower blood pressure.

It's an older drug, but it's safe and has a very long track record in pregnancy.

And what if it's acute?

If the pressure is dangerously high, like 160 over 110 right now?

Then we reach for the IV drugs, like hydrolazine or libetalol.

Hydrolazine is a direct arteriole vasodilator.

It just forces the arteries to open up.

Libetalol is a beta blocker.

These act much faster to bring that dangerous pressure down and prevent a stroke.

But then we have magnesium sulfate again.

And this is so crucial for listeners to understand, in this context, we are not using it to lower blood pressure, are we?

That is the single most important distinction in this entire chapter.

In the setting of preeclampsia, magnesium sulfate is used for the prevention and treatment of seizures.

It is an anticonvulsant.

It might lower the blood pressure a little bit as a side effect.

A little bit maybe, but that is not the goal.

The primary goal is to sedate the central nervous system to raise the seizure threshold so the brain doesn't short -circuit into a seizure.

Okay, so we are pumping this potent CNS depressant into the patient.

But the line between a therapeutic dose and a toxic dose is razor thin.

Very, very thin.

The therapeutic range we are aiming for is 4 -7 mEq per liter.

And what happens if we go higher than that?

The text gives us very specific stop signs.

This is where the nurse at the bedside earns their keep.

Absolutely.

The nurse is the surveillance system.

The very first sign of toxicity usually occurs at levels of 8 -10 MeqL.

And that is the loss of deep tendon reflexes, or DTRs.

So you are tapping the knee with a reflex hammer.

And you get nothing.

Hyperflexia or complete arphyflexia.

If the reflexes are gone, it means the neuromuscular blockade is becoming too strong.

You must stop the infusion immediately and notify the provider.

And if you don't stop it, what's the next sign?

At levels around 10 -15 MeqL, you get respiratory depression.

The diaphragm is a muscle.

Magnesium relaxes it.

If the patient's respiratory rate drops below 12 breaths per minute, you are in the danger zone.

And eventually, if it keeps going.

Cardiac arrest.

At levels greater than 20 or 25 MeqL, the heart, which is also a muscle, will stop.

There is also a critical metric regarding urine output.

Yes.

Urine output must be at least 30 mL per hour.

Why?

Because magnesium is excreted 100 % by the kidneys.

If preeclampsia has damaged her kidneys and she stops making urine, the magnesium is not leaving her body.

It will accumulate rapidly to toxic levels.

The nurse is basically living at the bedside, checking reflexes, counting respirations, measuring urine output every single hour.

Continuous one -on -one monitoring.

Plus, keeping the environment low stimulation,

dim the lights, keep the room quiet to help prevent triggering a seizure, and you must always have the antidote ready on the bedside.

Calcium gluconate.

One gram given by IV, push over three minutes.

Calcium directly antagonizes the effects of magnesium.

Right.

It reverses the paralysis.

If you see respiratory depression or the reflexes disappear, you push the calcium.

What about the baby?

Magnesium crosses the placenta very easily.

It does.

We often call it the floppy baby syndrome.

The newborn will show signs of that same neuromuscular depression,

lethargy, hypotonia, which is low muscle tone, and respiratory depression.

The NICU team needs to be prepped and present at the delivery if mom was on a magnesium drip.

This is such intense stuff.

Let's try to wrap up with section seven, the nursing process and patient safety highlights from the chapter.

We covered a lot of it, but a few key safety double checks stand out.

There is a huge look -alike, sound -alike drug warning that we absolutely need to reiterate.

This is between methylurganavine and tributyline.

Right.

They often come in similar packaging little ampules, but they do the exact opposite things.

Tributyline stops contractions for preterm labor.

Methylurganavine or methadiene stimulates powerful contractions to treat postpartum hemorrhage.

So if you mix these up.

If you give methylurganavine to a pregnant woman in preterm labor, you will cause massive violent titanic contractions.

You could rupture the uterus.

It is a catastrophic never event error.

You must read the label.

Read it again.

Patient teaching is also huge.

Let's just hit the big three one more time.

Caffeine, alcohol, smoking.

For caffeine,

the general recommendation is to limit it to one cup a day, which is about 200 milligrams.

The fetus can't metabolize caffeine effectively.

It stays in their system and can alter their heart rate and movement patterns.

Alcohol.

There is no safe level determined.

Just avoid it completely.

Fetal alcohol syndrome is 100 % preventable.

And smoking.

Smoking causes vasoconstriction.

It clamps down on the blood vessels, reducing blood flow to the placenta.

This leads to low birth weight, nutrient loss, and an increased risk of preterm birth.

And there was a brief mention of a clinical judgment case study regarding magnesium sulfate discharge criteria.

Right.

It's just there to emphasize the importance of recognizing when a patient is stable.

Even after the acute phase of preeclampsia is managed, you have to ensure uterine contractions are reduced if she was in preterm labor and that her vital signs and reflexes are stable before she can be discharged.

You can't just unhook the IV and say, good luck.

There needs to be a very careful transition.

So what does this all mean?

We've covered everything from taking your vitamins with orange juice to managing a life -threatening seizure with magnesium.

It really brings us back to that initial thought we had.

The immense responsibility of the nurse in monitoring this two -patient system.

You are the early warning system.

You are the one checking the DTRs, noticing the urine output drop, catching that black box warning on the tributyline, and teaching the patient to avoid eggs with her iron.

It really highlights that pharmacology isn't just about passing pills.

It's about deeply understanding the physiology behind everything you do.

And here is a final provocative thought to chew on.

We spent so much time in this chapter discussing drugs to colitics, antihypertensives, magnesium.

But in the case of preeclampsia, which is arguably the most dangerous condition we discussed, the only true drug that cures the disease isn't a drug at all.

What is it?

It's the delivery.

The birth itself is the cure.

Exactly.

Everything else is just buying time.

It completely reframes how we look at pharmacological management in these cases, not as a fix, but as a bridge to safety.

That is a really powerful way to look at it.

Thank you so much for breaking this incredibly dense chapter down with us.

My pleasure.

It's a complex chapter, but mastering it saves lives.

It really does.

And to our listeners,

thank you for trusting the Last Minute Lecture Team with your review.

We'll see you on the next Deep Dive.

Study hard and stay safe.