Chapter 19: Laboratory & Diagnostic Tests in Older Adults

Welcome to Last Minute Lecture.

This free chapter overview is designed to help students review and understand key concepts.

These summaries supplement not replaced the original textbook and may not be redistributed or resold.

For complete coverage, always consult the official text.

Welcome back to the Deep Dive.

We are so glad you're here because today we are tackling a stack of materials that, I'll be honest, might look a little intimidating at first.

It's a bit of a heavy lift.

It is.

We are breaking down chapter 19 of Gerontologic Nursing by Sue E.

Minor.

And a title is Laboratory and Diagnostic Tests.

Exactly.

And I think for a lot of nursing students, maybe even practicing clinicians, the first instinct is to think, okay, this is just memorization.

Right.

Give me the reference ranges, let me memorize the numbers, and I'm good.

But as I was reading through this, I realized that that approach is actually, well, it's dangerous.

It is.

It's a complete trap.

If you treat geriatric lab values like a multiplication table you just have to memorize, you are going to miss the entire story.

The entire story of what's happening inside the patient's body.

Exactly.

Because the body changes.

So the premise we're working with today is that reading a lab report for an older adult, we're talking someone who's 70, 80, 90 years old, it's like trying to read a map where all the landmarks have shifted.

That's a great analogy.

A really great one.

Right.

I mean, you've got this map you use for a 30 -year -old, you know where normal is, you know where danger is.

But then you take that same map and you apply it to an 85 -year -old body and suddenly the streets have moved.

What looks normal on your map might actually be a crisis for them.

And what looks abnormal might be perfectly fine.

Yes, precisely.

And if you follow that old map, you are going to get lost.

And in nursing, getting lost means missing a diagnosis.

It means over treating something should be left alone.

So our mission for this deep dive is to, you know, redraw that map.

We're going to translate this really technical medical text into a kind of survival guide.

And the text gives us a really solid framework to start with.

Before we even get into specific blood cells or, you know, electrolytes.

Miner outlines this three groups concept for lab values in aging.

Can you break that down for us?

Yes.

This is your mental sorting hat.

Before you even look at a number on a lab sheet, you need to know which bucket it falls into.

So group one,

these are values that just change with aging.

It's purely physiological.

The body gets older.

The number shifts.

It's expected.

So if it looks off compared to a textbook for a young adult, it might actually be perfectly normal for your patient.

Exactly.

Then you have group two.

These are the values that do not change with aging.

These are the stubborn ones.

They should So if these numbers shift,

it's not because the patient is old.

No, because they're sick.

It's a sign of pathology.

That is a crucial distinction.

Okay.

And the third group.

Group three is the gray zone.

These are values where the medical literature is a bit murky.

We aren't 100 % sure if the changes we see are because of normal aging or if they're because of the chronic diseases that just happen to come along with aging.

So you have to keep an open mind for those ones.

You do.

Now, before we stick a needle in anyone's arm, we have to talk about the human element.

The tech spent some real time on the physical and psychosocial reality of this.

It's not just data collection.

It's an invasive procedure.

And you have to think about the physical changes in an older adult.

They lose subcutaneous tissue.

That fatty cushion under the skin is just gone.

So their veins get more fragile.

So fragile.

They roll easily.

A blood draw isn't just a quick pinch for them.

No, it can be really painful.

And it's very likely to cause bruising, hematomas.

You have to be incredibly gentle and skilled.

And then you layer on top of that the psychosocial factors.

There's often anxiety about the cost.

Can I afford this test?

Or anxiety about privacy.

And there was a specific cultural note in the text that I found just fascinating.

It mentioned Chinese and Vietnamese beliefs specifically.

Yes.

And this is so important for cultural competence.

In some traditional Chinese and Vietnamese frameworks, blood is viewed as a vital energy source, a life force.

It's not seen as something the body just rapidly replaces.

Not at all.

It's not like a renewable resource.

It's seen as a non -replaceable essence of life.

So imagine a nurse comes in to draw blood and then has to come back two hours later because the lab messed up and needs another tube.

Right.

To the nurse, that's just an annoyance.

It's frustrating.

But to the patient holding these beliefs, that is a permanent loss of vitality.

They might get very upset.

And if you don't understand that cultural context, you might label them as difficult or confused when in reality they're just operating from a completely different worldview.

That brings us to what I think is the golden rule of this entire chapter.

I know you're going to say.

Treat the patient, not the paper.

Always.

Every time.

A number is just ink on a page until you correlate it with the person sitting right there in the bed.

All right.

Let's open up the hood and look at the engine.

We're going to go system by system, starting with hematology, the blood cells.

First up, red blood cells or RBCs.

What's the baseline here?

Does our blood just get tired as we age?

It's interesting.

The red blood cell itself is a sturdy little worker.

Its lifespan is about 120 days.

And that doesn't change whether you're 20 or 90.

The cell itself works just fine.

So the problem isn't the worker.

It's the factory.

It's the factory, the bone marrow.

The bone marrow activity diminishes as we age.

The hematopoietic tissue, the tissue that actually makes the blood just decreases.

So under normal, calm conditions, an older adult can maintain a normal red blood cell count.

They can cruise along just fine.

No problem.

But what happens if there's a crisis, a major bleed?

That's where the system fails.

If there is significant bleeding or a sudden demand for blood, the older bone marrow is like an old factory.

It cannot ramp up production quickly.

It takes much, much longer to replenish those lost cells compared to a younger person.

And this leads us directly to the anemia rule.

The text was so emphatic about this, and I want to make sure we underline it five times.

If you take one single thing away from the hematology section, let it be this.

Anemia is common in the elderly, but it is never normal.

Never normal.

Yeah.

I feel like that runs counter to what a lot of people just assume.

You know, you see an 85 year old who's pale and tired and you think, well, they're old, their blood is probably just a little thin.

And that assumption is a clinical error, a huge one.

Anemia is not a diagnosis.

It is a symptom.

It's a smoke signal.

It means there is a fire burning somewhere else.

And that fire could be a nutritional deficiency.

It could be renal failure.

Or very commonly, it could be a GI bleed.

So if you dismiss the anemia as just old age,

you are literally ignoring the smoke signal while the house burns down.

Exactly.

You're missing the underlying pathology and assessing it is tricky because the signs look so different.

In a 30 year old, if their blood count plummets, they might look ghostly pale, their heart races, they might faint.

It's very dramatic.

But in an older adult, their bodies have often adapted to a much slower decline.

So the symptoms are subtle, just fatigue, maybe a little breathlessness when they walk to the mailbox.

Or, and this seems to be the big one in geriatrics confusion.

It really is.

The brain is the first organ to complain when oxygen delivery drops.

So don't look for the drama, look for the subtle decline in function.

Now there's a bit of a debate in the text

about hemoglobin and hematocrit levels, right?

There is.

This falls into that group three gray zone we talked about.

Some studies say the levels stay exactly the same.

Others, like the Sarkozy study mentioned in the text, suggest they decline slightly after age 90.

But there's a massive trap here involving hematocrit.

The dehydration trap.

Yes, tell us about that.

Okay, so hematocrit is basically a measure of how much of your blood volume is made of solid cells versus liquid plasma.

A percentage, basically.

Exactly.

And if an older adult is dehydrated, which they so often are, their plasma volume drops, the liquid part goes down.

Which makes the cells look more crowded or concentrated.

Precisely.

The percentage of cells goes up.

So you might look at the lab and see a normal or even a high hematocrit and think, wow, great blood count.

But what's really happening?

They are actually anemic and dehydrated.

As soon as you hydrate them, you put that liquid back in the vessels and that hematocrit number plummets.

Suddenly you see the true picture and you see the anemia.

So a high hematocrit in an older adult should make you think, check for dehydration.

Always.

Every single time.

Let's move to the defenders, the white blood cells.

This part of the chapter gave me chills, actually, because it talks about the concept of the silent infection.

This is a critical, critical safety issue.

In a healthy young adult, the immune system is aggressive.

If you get pneumonia, your body pulls the fire alarm.

You get a high fever, you get the chills.

And your white blood cell or WBC count shoots through the roof to fight the bacteria.

We rely on that.

Fever plus a high WBC count equals infection.

That's the formula we all learn.

But in the elderly, that formula breaks.

The total WBC count usually doesn't change much with age, but the function of those cells declines.

This is called immunosenescence.

And if a bone marrow doesn't have the same reserve to release that massive army of neutrophils.

Exactly.

The army doesn't show up in force.

So they get the infection, but the army just sort of trickles in.

It trickles in.

So you might see a patient with severe sepsis, but their WBC count is only slightly elevated.

It might even still be within the normal range.

And the scariest part.

The lack of fever.

The text is very clear that the immune response is so dampened that an older adult can have a major infection like pneumonia with no fever at all.

That is absolutely terrifying.

If you're a nurse waiting for a fever to tell you that your patient is sick, you might be waiting until it's way too late.

Precisely.

The classic signs are missing.

So if the alarm system is silent,

how do we know something is wrong?

You have to become a detective of behavior.

You look for sudden changes in their function,

confusion, delirium, lethargy, this concept of failure to thrive.

So if a patient who is usually chatty and engaged is suddenly just staring at the wall and confusing you with her sister.

That is her fever.

You don't check her forehead.

You check her lungs and her urine.

That change in mental status is the sign of infection.

That is such a vital takeaway.

The confusion is the fever.

It is.

Let's quickly touch on platelets in the ESR before we move on.

Platelets generally stay unchanged, but there is one condition to watch for.

If you see a drop in everything, low red cells, low white cells, and low platelets, that's called pancytopenia.

And in someone over 70, that's a huge red flag.

It's a huge red flag for Myler's flastic syndrome or MDS, which is a type of bone marrow failure Got it.

What about the ESR, the erythrocyte sedimentation rate?

This is a nonspecific marker of inflammation.

And the key here is that the ESR naturally rises with age.

It's one of those group one changes we talked about at the beginning.

Exactly.

A mild elevation, like a 10 to 20 millimeter rise, can be a completely normal age -related change.

It doesn't necessarily mean they have a hidden infection.

It just means they're older.

So don't chase a ghost if the ESR is just a little bit high.

Don't chase the ghost.

All right.

Let's move to section two, nutritional anemias and clotting.

We're talking vitamins and minerals here.

Let's start with folic acid and B12.

Folic acid is pretty straightforward.

The levels tend to remain unchanged.

If they're low, it's usually because the patient isn't eating well, malnutrition, or they're abusing alcohol.

But vitamin B12, that is the big story here.

The text mentioned the prevalence of B12 deficiency is massive.

It's huge.

Around 25 % of the elderly population.

And the reason isn't always their diet.

You can eat plenty of B12, but as you age, your stomach changes.

How so?

You produce less stomach acid and less of something called intrinsic factor, which is a protein you absolutely need to absorb B12 from your food.

Plus you have to look at the medication list.

Oh, absolutely.

Proton pump inhibitors for acid reflux, metformin for diabetes, both of those are notorious for blocking B12 absorption.

And the symptoms are just particularly cruel because they look exactly like aging.

They do.

B12 is essential for maintaining the myelin sheath, the insulation on your nerves.

When B12 is low, that insulation starts to break down.

You get neurological symptoms.

You get peristhesias, numbness, and tingling in the feet.

You get balance issues.

And significantly, you get memory loss and cognitive decline.

Looks like dementia.

It looks exactly like dementia or diabetic neuropathy, but it's a vitamin deficiency.

And if you catch it early and you treat it, you can reverse it.

If you miss it, that nerve damage becomes permanent.

That's a powerful so wet for the listener.

Check the B12 before you label someone with dementia.

Okay, now let's talk about iron.

Iron deficiency is the number one cause of anemia in the elderly.

Now, serum iron levels do drop naturally with age, but the body's ability to absorb it stays intact.

So if an older adult has iron deficiency anemia, the rule is?

Blood loss until proven otherwise.

They're bleeding from somewhere.

And usually the GI tract, right?

Usually the GI tract.

So you have to check for occult or hidden blood in the stool.

And here is a very practical, very gross, but very important nursing tip from the text about those stool tests.

Yes.

This is the classic, gotcha.

So you have a patient with anemia.

You put them on iron supplements to help build their blood back up.

Makes sense.

Then you decide to test their stool for blood to see if they're bleeding internally.

But what do iron supplements do to the color of stool?

They turn it pitch black.

And what does a GI bleed do to the color of stool?

It turns it pitch black.

I see.

You see the problem.

It's a visual mess.

It's not just a visual mess.

It's a chemical mess.

The iron in the supplement can actually interfere with the regent in the fecal occult blood test and give you false results.

So what's the rule?

The text explicitly says patients must stop taking their iron supplements for three days before you do a fecal occult blood test.

Three days.

That is a detail that prevents a misdiagnosis.

Okay.

Let's talk about clotting, coagulation, specifically the drug warfarin, also known as Coumadin.

Ah, the bane of many nurses' existence.

Warfarin is an anticoagulant used for things like atrial fibrillation.

The problem is it interacts with everything.

Antibiotics.

And saline.

Supplements.

You name it.

They all mess with its effectiveness.

And we measure its effect with the PT and INR test.

Right.

The INR is the standard.

For most conditions like AFib, we want an INR between 2 .0 and 3 .0.

If they have something like a mechanical heart valve, we need the blood even thinner so the target is higher, like 3 .0 to 4 .0.

There's a dietary note here that I really want to clarify because I hear this myth all the time.

If you're on warfarin, you can't eat salad.

That is a total myth, but it's based on some real science.

Warfarin works by blocking vitamin K.

And leafy greens like spinach and kale are full of vitamin K.

Exactly.

So in theory, if you eat a big salad, you're working against the drug.

So what do people do?

They stop eating veggies.

Which is terrible for their health.

It is.

The text clarifies the goal here.

The goal isn't avoidance.

The goal is consistency.

You can't eat broccoli.

Just eat the same amount of broccoli every day.

So if you're consistent, the dose can be adjusted around your diet.

Yes.

The danger is the binge.

Don't have a giant kale smoothie feast on Tuesday and then zero greens on Wednesday.

That's what throws the INR all over the place.

Consistency is key.

Got it.

Let's shift gears to section three.

Blood chemistry.

Electrolytes.

These are the sparks that keep the engine firing.

Let's start with sodium.

Sodium is all about the brain and fluid balance.

In the elderly, hyponatremia low sodium is the most common electrolyte disorder you will see, period.

And why is it so common?

It's the kidneys again.

As they age, they lose their ability to excrete free water.

They just hold on to water.

And when you hold on to too much water, you dilute the sodium that's in your blood.

And the symptoms are primarily neurological, right?

Because of brain swelling.

Yes, exactly.

So you see things like malaise, headache, confusion.

If it gets low enough, you can see seizures and even coma.

But there's a tricky concept in the text called pseudo hyponatremia.

Yes, false low sodium.

This happens when the lab report says the sodium is low, but the patient's actual fluid balance is fine.

Their osmolarity is normal.

What causes that?

It can happen if the patient has very high protein levels or more commonly very high glucose levels.

All that extra stuff in the blood throws off the volume measurement in the test tube.

So don't panic and start treating the sodium until you've checked the glucose and the osmolarity.

Exactly.

Don't treat a lab error, treat the patient.

On the flip side, hypernatremia, high sodium is almost always a sign of dehydration.

Or?

Or, as the text politely puts it, unreported laxative abuse, a very common cause of fluid loss in the elderly.

Okay, what about potassium?

This is the one that always scares me because of the heart connection.

It should scare you.

The cardiac muscle is incredibly sensitive to potassium shifts.

Too high or too low, and you can get lethal arrhythmias.

And the text points out that for the elderly, the danger usually comes from the medicine cabinet.

It's almost always the meds.

Potassium sparing diuretics, NSAIDs like ibuprofen.

And here's a sneaky one that I love that the text included.

Salt substitutes.

Wait, the stuff people buy to be heart healthy?

Yes.

Imagine an older adult with heart failure.

The doctor says, stop eating salt.

So they go to the store and they buy no salt or a similar brand.

Well, regular salt is sodium chloride.

No salt is often pure potassium chloride.

Oh, no.

So they go home, they make a bowl of soup, and they shake a massive amount of pure potassium onto it because they think it's safe.

If they're also taking a medication that makes them hold onto potassium, they can spike their levels into a lethal range just by trying to be healthy.

That is a terrifyingly easy mistake to make.

It is.

Conversely, low potassium hypokalemia is usually from losing fluids, like from vomiting or diarrhea.

And there is a critical drug interaction here.

Digoxin.

Digoxin toxicity.

If a patient is on digoxin for their heart and their potassium level drops, the digoxin binds much more strongly to the heart muscle.

It potentiates the drug's toxicity.

So a normal dose of digox effectively becomes an overdose if the potassium is low.

It's a medical emergency.

Wow.

Okay, let's round out the electrolytes with calcium, phosphorus, and magnesium.

Calcium is deceptive.

Blood levels of calcium usually stay stable throughout life.

But that is actually a lie that the body tells you.

How is it a lie?

The body knows that the heart and nerves need calcium to function.

It prioritizes the blood level of calcium above everything else.

So if you aren't eating enough calcium, or if you aren't absorbing it well, which is very common in aging, the body will steal calcium from your bones to keep the blood levels normal.

So the blood test looks perfect.

But the bones are dissolving.

That's osteoporosis.

The blood is robbing the bank to pay the rent.

That is a perfect analogy.

And magnesium.

Magnesium actually drops.

The levels decrease by about 15 % between our 30s and our 80s.

The kidneys just stop reabsorbing it as efficiently.

Speaking of kidneys,

we have arrived at section four,

the renal system.

And I want to pause here because I think this is the single most important physiologic takeaway of this entire chapter for nursing students.

We're talking about the creatinine trap.

I agree completely.

If you are listening and you are a student, you need to tattoo this on your brain.

Let's walk through it slowly.

Serum creatinine is the standard blood test we use to check if kidneys are working right.

Right.

It's a waste product.

If the kidneys are working, they filter it out and the blood level stays low.

If the kidneys fail, the level rises.

Simple.

Simple enough.

But where does creatinine come from?

It comes from muscle breakdown.

It's a byproduct of muscle metabolism.

And what happens to muscle mass as we age?

It decreases significantly.

The medical term is sarcopenia.

An 85 -year -old woman has a fraction of the muscle mass of a 25 -year -old linebacker.

So she is producing much, much less creatinine to begin with.

Exactly.

So let's do the math here.

She has tiny muscles, so she makes very little waste.

Our kidneys are also old and maybe they're only working at 50 % capacity.

But because the input of waste is so low, the backlog doesn't build up very high.

Her serum creatinine might be, say, 0 .9.

And 0 .9 is a normal number on the lab sheet.

It's right in the middle of the reference range.

It looks perfect.

It looks like she has the kidneys of a teenager.

But in reality, that 0 .9 is masking a significant failure.

If she had normal muscle mass for her size, her creatinine would be 2 .0.

So the number is a lie.

It is a dangerous illusion.

Because if a doctor looks at that 0 .9 and prescribes a medication that needs to be cleared by the kidneys, they might give her a standard dose.

But her kidneys can't handle it.

They can't.

The drug builds up and she becomes toxic.

So never trust serum creatinine alone in the elderly.

What's the solution?

What do we look at instead?

You have to look at the creatinine clearance or, even better, the GFR, the glomerular filtration rate.

The GFR is a calculation.

It takes the creatinine number and it adjusts it for age, gender, and sometimes weight.

It corrects for that muscle loss.

So GFR is the true measure.

GFR is the only true measure of kidney function in geriatrics.

GFR is king.

Got it.

What about BUN, blood urea nitrogen?

BUN is messy.

It reflects kidney function, sure.

But it also goes up if you're dehydrated, if you eat a high -protein diet, or if you have a GI bleed.

It's just too nonspecific to be the sole judge of the kidney.

Let's move to section five.

Glucose, proteins, and lipids.

Diabetes is obviously a huge topic.

It is.

The diagnostic criteria don't change a fasting glucose over 126 or an HbA1c over 6 .5 percent.

And the HbA1c is a fantastic tool because it measures the glucose attached to red blood cells over their lifespan.

So it gives you a two to three month average of blood sugar control.

It's the truth serum.

You can't fake an A1c by eating a salad the morning of your appointment.

But while the diagnosis is the same, the way high blood sugar presents is different in older adults.

Very different.

In younger type 1 diabetics, we worry about DKA diabetic ketoacidosis.

They burn fat for energy and produce acid.

But older adults are usually type 2.

Right.

They still produce a little bit of insulin, just enough to stop the body from burning fat and making acid, but not enough to control the sugar.

So they don't get DKA.

They get something called HHS.

Hyperosmolar hyperlycemic state.

And it is intense.

Their blood sugar gets incredibly high.

I'm talking 600, 800, even over a thousand.

This basically turns the blood into syrup.

And what triggers it?

It's usually driven by an infection or severe dehydration.

They get confused, very dry, and can slip into a coma.

But their breath doesn't smell fruity like in DKA.

And what about the other end of the spectrum?

Low blood sugar hypoglycemia.

This is so much harder to spot in the elderly.

Younger people get the shakes, the sweating, the palpitations.

It's a very clear alarm.

But in older adults?

They might just get confused.

Confusion again.

The universal sign.

If an older patient is suddenly acting strained or foggy, check their blood sugar immediately.

It might be 40.

Let's touch on proteins, specifically albumin.

Albumin is a protein made by the liver.

And it's a marker of long -term nutritional status.

Its half -life is about 21 days.

And if it's low?

If albumin is low, under 3 .5, it's a bad sign.

It predicts poor wound healing, edema, and higher mortality rates.

But because it changes so slowly, it's not great for quick checks on interventions.

Exactly.

If you start feeding a malnourished patient today, their albumin won't budge for weeks.

That's why we use pre -albumin.

It has a half -life of only two days.

It tells you if your nutritional intervention is working right now.

Section 6 takes us to specific organs.

Cardiac, thyroid, and prostate.

For the heart, we're looking at troponin and BMP.

Troponin is the gold standard for heart damage.

If heart muscle dies, like in a heart attack, troponin leaks into the blood.

And it stays elevated for up to two weeks.

Which is really helpful in geriatrics.

It's so helpful because older adults often have silent heart attacks.

They don't always get that classic crushing chest pain.

They might just have felt weak or had bad indigestion a week ago.

Exactly.

The troponin test allows us to look back in time and say, yes, you did have a cardiac event.

And what about BMP?

Brain Natriuretic Peptide.

You can think of this as the stretch hormone.

It's released when the ventricles of the heart are overfilled and stretched out.

Which happens in heart failure.

Precisely.

So if a patient comes in wheezing and short of breath, and you don't know if it's their lungs, like from COPD or their heart, you check the BMP.

If it's high, it's the heart.

Now the thyroid.

This is another one of those areas where the symptoms play hide and seek.

Hypothyroidism, low thyroid function is very common, especially in women over 65.

But the symptoms mimic aging perfectly.

In a young person, low thyroid means weight gain, feeling cold, hair loss.

But in an older adult?

It often presents as depression, Depression?

Apathy, withdrawal,

and weight loss.

Which is the complete opposite of the classic symptom.

They just stop eating.

We call it failure to thrive.

So if you have an elderly patient who seems depressed and withdrawn, don't just refer them to psych.

Check their TSH, their thyroid stimulating hormone.

It might be a simple hormone fix.

And finally, in this section, the prostate and the PSA test.

This is a bit of a controversy in the medical world, isn't it?

It is.

The PSA prostate -specific antigen is a marker for prostate health.

But it is not specific to cancer.

It goes up if you have an infection or if you just have BPH benign prostatic hyperplasia.

Which almost all men get as they age.

Exactly.

So an elevated PSA is very, very common.

The real controversy is about screening.

The USPSTF guidelines now suggest that for men over 75, we shouldn't be routinely screening for prostate cancer.

That sounds really counterintuitive.

Why would we stop looking for cancer?

It comes down to the nature of the disease versus the patient's lifespan.

Prostate cancer in an 80 -year -old is often extremely slow -growing.

It's very likely that the patient will die with the cancer, not of the cancer.

With the treatment for it.

The treatment surgery, radiation carries heavy risks, incontinence, impotence, bowel issues.

So the argument is, why ruin the quality of life for a man's final years to treat a cancer that probably wasn't going to kill him anyway?

That's a heavy ethical weight to balance.

It's quality of life over quantity of life.

Precisely.

Section seven, urine chemistry, myths and realities.

Let's bust the biggest myth first,

the smell test.

Oh, this is a classic.

There's a fantastic evidence -based practice box in the text about this.

It details a study where they actually tested this theory.

Nurses and nursing assistants often believe that if urine smells foul, it means the patient has a urinary tract infection or a UTI.

It seems like common sense.

Bad smell equals bacteria.

But the study showed that the nose is a terrible diagnostic tool.

They had staff members smell the incontinence pads of nursing home residents.

The result, foul smell was usually just a sign of dehydration or poor hygiene.

It was not a reliable predictor of actual infection.

So smell is not evidence -based practice.

No, do not treat a smell with antibiotics.

And speaking of treating, let's talk about bacteria urea.

Just have bacteria in the urine.

Here's the reality.

Bacteria in the urine is common in older adults.

Their bladders often don't empty completely, which creates a little pool where bacteria can hang out.

We call this colonization.

So if you dip their urine, it will show bacteria.

Do we treat it?

This is the rule.

If the patient is asymptomatic, no fever, no pain, no burning, you do not treat it.

Asymptomatic bacteria urea should be left alone.

Why not?

Because if you throw antibiotics at it, you aren't fixing a problem because they aren't actually sick.

You are just teaching the bacteria how to resist the drug.

You create superbugs.

So no symptoms, no drugs.

What about puss in the urine?

Peuria.

Peuria, the presence of leukocytes or white cells, is a better predictor of a real infection.

But even then, you have to look at the whole clinical picture.

One more thing on urine -specific gravity.

This measures how concentrated the urine is.

In the elderly, specific gravity generally decreases.

The kidneys just lose their ability to concentrate urine.

So even if the patient is dehydrated, their urine might still look dilute and watery.

And the glucose threshold.

What's that about?

This is fascinating.

Normally, if your blood sugar gets high, say around 180, the kidneys can't hold on to all of it and sugar spills into the urine.

That's how the old urine dipsticks for diabetes worked.

Right.

But in older adults, that spillover point rises.

They can have a blood sugar of 200, 250, even 300, and their kidneys will still hold on to all of it.

The urine will be negative for glucose.

So urine testing for diabetes management in the elderly is?

Useless.

Completely unreliable.

You have to use a finger -stick blood test.

Section 8, arterial blood gases, or ABGs, and drug monitoring.

Let's talk about oxygen.

We're going right back to our shifting map analogy.

If you draw an ABG on an 80 -year -old, you have to expect their pay -o -to, their arterial oxygen level, to be lower than yours.

It drops naturally with age.

It does.

It drops about 25 % between age 30 and age 80.

The lungs just aren't as efficient at gas exchange.

And there's a formula in the text for this, isn't there?

Yes.

It's pay -o -to equals 109 minus 0 .43 times the patient's age.

I am definitely not doing that math in my head right now, but just give me the so -what.

The so -what is that a pay -o -to of 75 millimiller -Hg would be considered hypoxic for a 30 -year -old.

You'd be rushing to put oxygen on them.

But for an 80 -year -old, that can be perfectly normal.

Normal moves.

Normal moves.

And if you over -oxygenate them based on the wrong map, you can actually suppress their drive to breathe.

And finally, drug monitoring.

The narrow window.

This really sums up everything we've talked about regarding the kidneys and the liver.

Older bodies just don't clear drugs as fast.

So the window between this drug is helping and this drug is killing you gets very, very tiny.

The text lists three main culprits that nurses need to watch like a hawk.

Digoxin, phenytoin, and theophylline.

We mentioned digoxin.

The signs of toxicity are so subtle, confusion, loss of appetite, seeing halas around lights.

And remember, it can happen even at normal blood levels if their potassium is low.

And phenytoin.

That's Dilantin for seizures.

Toxicity looks like drunkenness.

Ataxia, which is stumbling, slurred speech, confusion.

If an older patient on Dilantin starts acting like they've had a few too many drinks, you need to check the level.

And theophylline.

I don't see that used as much anymore.

For very good reason.

It's a bronchodilator.

But the risk of toxicity, arrhythmias, seizures is so high in the elderly that the text suggests it's largely prohibited or used with extreme caution.

It's just too risky.

Okay, we have covered a massive amount of ground.

We have redrawn the map of the geriatric body.

Let's try to summarize the big three takeaways for our listeners before we let them go.

Challenge accepted.

Let's do it.

Okay, number one.

The creatinine trap.

Never, ever trust serum creatinine alone.

It lies because of muscle loss.

Always look at the GFR to judge kidney function.

Number two.

Infection is silent.

Do not wait for a fever.

If an older patient is confused, lethargic, or just not themselves, you have to assume infection until proven otherwise.

The behavior is the symptom.

And number three.

Context is king.

Whether it's the PO2 dropping, the ESR rising, or the bacteria in the urine, you cannot interpret a number without looking at the age and the person.

Normal is a moving target.

So the nurse's role is really that of an interpreter, isn't it?

Exactly.

You are the one standing between the raw data and the patient.

You have to advocate.

When a provider wants to ignore the confusion because there's no fever, you speak up.

When they want to treat a smell with antibiotics, you speak up.

You treat the patient, not the paper.

That brings us to our final thought.

A little scenario to leave you with.

Straight from the critical thinking exercise in the text.

I love this one.

Okay, so picture an 82 -year -old woman.

It's August.

It's hot outside.

But she is wearing a sweater and she's complaining of being cold.

She's constipated.

She's tired all the time.

She's not eating much.

The easy answer is to say, well, she's 82.

Old people get cold.

Old people get constipated.

Just give her a blanket and a laxative and move on.

That's the old map answer.

The deep dive answer is?

Check her thyroid.

Exactly.

Those are the classic sneaky signs of hypothyroidism in the elderly.

The lab values are the clues to the silent struggles of the aging body.

It's your job to find them.

Thank you so much for listening.

This has been a deep dive into the hidden world of geriatric diagnostics.

Keep learning and keep looking closer.

We'll catch you on the next one.

This is the Last Minute Lecture Team signing off.