Fluid Volume Deficit (Dehydration)
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Welcome to MedSimu Nursing Podcast.
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Today, we're doing a deep dive into a really crucial topic,
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especially if you're prepping for the NCLEX,
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fluid volume deficit, dehydration.
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It sounds basic, maybe, but the details
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are so important for patient care.
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We're joined by an expert who can really unpack this for us.
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Welcome.
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Glad to be here.
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It's definitely fundamental.
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Understanding fluid volume deficit well is just non-negotiable for safe nursing.
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Absolutely.
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So at its heart, dehydration is simply when the body's fluid output is more than its intake.
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Pretty straightforward concept there.
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But the treatment goals, they're threefold, really.
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Restore the fluid volume, replace any lost electrolytes, and crucially, fix whatever caused the deficit to begin with.
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OK, so it's definitely more complex than just telling someone to drink water.
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Oh, absolutely.
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Now the background information we looked at breaks dehydration down, different type, right?
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That's correct.
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We typically talk about three main categories, isotonic, hypertonic, and hypertonic dehydration.
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And each one has, you know, its own specific characteristics, different implications for
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the patient.
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Let's start with isotonic then.
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What's the main takeaway for that one?
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Okay, so isotonic dehydration.
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This is where the body loses both water and electrolytes, sodium, chloride, things like
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that in pretty much equal proportions.
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- Okay, equal loss.
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- Exactly.
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And it's actually the most common type you'll encounter.
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You'll often hear it called hypovolemia.
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- Hypovolemia, right.
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- The big problem here is the decrease
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in circulating blood volume.
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Less volume means less effective perfusion,
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less oxygen getting to the tissues.
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- And that impacts everything.
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- It really does.
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And you know, something really important,
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especially thinking about exams
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like the NCLEX hypovolemia, can get serious fast,
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particularly in patients who already have heart issues.
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You might see subtle vital sign changes
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even before their blood pressure tanks.
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Those are key early warnings.
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- That's a critical point, speed matters.
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So what causes this isotonic type?
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What are the triggers?
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- Well, several things.
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It could just be inadequate intake,
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not drinking enough and not getting enough electrolytes.
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- Makes sense.
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- Or you could have fluid shifts
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where fluid moves out of the blood vessels into other spaces
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and then there are excessive losses of fluids
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that are isotonic themselves, like I think significant bleeding or prolonged vomiting
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or diarrhea.
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Okay, got it.
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Bleeding, vomiting, diarrhea, classic causes.
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So that's isotonic.
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How is hypertonic dehydration different?
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Right, hypertonic.
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Here the key difference is that the body loses more water than it loses electrolytes.
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More water loss.
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So this imbalance changes the concentration of salutes like sodium in the blood plasma.
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It gets more concentrated.
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And because the environment outside the cells is now more concentrated than inside, water
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gets pulled out of the cells, osmosis basically.
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So the cells actually shrink.
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Exactly.
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The fluid shifts from the intracellular space to the extracellular space, causing cellular
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dehydration.
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The cells themselves are losing water.
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Wow, okay.
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That sounds potentially quite damaging at a cellular level.
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What kind of situations lead to that?
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Yeah, it can be serious.
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You see it in conditions where there's significant water loss without matching electrolyte loss.
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think excessive sweating, like with a really high prolonged fever, or patients who are
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hyperventilating, blowing off a lot of water vapor.
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Diabetic ketoacidosis is another one.
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C.K., right.
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Mm-hmm.
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Also severe watery diarrhea, some types of kidney problems like early renal failure,
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and a condition called diabetes insipidus, where the kidneys can't conserve water properly.
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So a different set of causes driving that water loss?
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Precisely.
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Okay.
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What about the third type, hypotonic dehydration?
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How does that contrast?
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- So, hypotonic is pretty much the flip side of hypotonic.
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In this case, the body loses more electrolytes
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than it loses water.
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- More electrolytes lost this time.
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- Correct, and again, the problems come from fluid shifts,
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but the direction is different.
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Here, the plasma becomes less concentrated
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than the inside of the cells.
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- So the fluid moves into the cells.
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- Exactly, fluid moves from the plasma
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and the interstitial space into the cells.
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This leads to a decrease in the circulating plasma volume,
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but also causes the cells to swell up.
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- Self-swelling, okay.
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And what situations typically cause
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hypotonic dehydration?
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- You often see this in patients,
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maybe with chronic illnesses.
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It can also happen, interestingly,
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if someone loses fluids and then replaces them
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only with fluids that are very low in electrolytes,
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like drinking huge amounts of plain water
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after sweating a lot.
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- Replacing loss with the wrong kind of fluid.
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- Yes, exactly.
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or excessive IV administration of hypertonic solutions.
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Other causes can include things like renal failure,
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especially later stages, and chronic malnutrition.
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- Okay, this breakdown is super helpful.
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Isotonic, hypertonic, hypotonic,
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different loss of different shifts.
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So as nurses on the floor are preparing
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for that NCLEX question,
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how do we spot fluid volume deficit?
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What are the key assessment findings?
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- Assessment is absolutely paramount
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and you need to look across multiple systems.
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Let's start cardiovascular.
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You might feel a pulse that's rapid, but weak and thready.
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- Okay, fast but weak pulse.
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- Yes, blood pressure will likely be low
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and you'll often see orthostatic hypotension,
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that dizziness or drop in BP when they change position,
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like sitting to standing.
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- Orthostatics, check.
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- You might notice their neck veins
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where the veins on the back of their hands
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like flat, collapsed, peripheral pulses radial,
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pedal might feel diminished, hard to find.
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And if they have a central line,
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you'd see a decreased CVP, central venous pressure.
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Even dysrhythmias can occur.
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- Okay, quite a few cardiac, what about breathing?
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Respiratory signs.
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- You might see an increased respiratory rate in depth,
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the body's trying to compensate, you know.
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- Makes sense, neuromuscular changes.
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- Yeah, this is important too.
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You could see decreased CNS activity.
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That might range from just lethargy seeming really tired.
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- Fluggishness.
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- Right, all the way to confusion or in severe cases,
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even coma.
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Fever can sometimes be present too.
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paradoxically and patients might complain of muscle weakness.
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- Okay, and the kidneys, they must show signs.
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- Absolutely, a classic sign is decreased urine output,
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oliguria, if the kidneys aren't getting perfused well,
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they just can't make much urine.
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- Low output, got it.
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- Yeah.
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- What about skin, that seems like a common check.
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- Definitely, you'll likely see dry skin,
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and that classic sign of poor skin turgor,
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you pinch the skin, maybe on the forearm or sternum,
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and it stays tented up instead of snapping right back.
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- Nothing right.
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mouth, dry mucous membranes are also common.
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- And GI system.
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Any clues there?
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- Yes, things tend to slow down.
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You might hear decreased or absent bowel sounds.
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Constipation can be an issue.
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The patient will almost certainly report feeling thirsty
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and look out for a recent unexplained weight loss.
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That can be a big indicator of fluid loss.
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- Thirst and weight loss.
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Okay, lastly, labs.
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What blood or urine tests help confirm it?
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- Several labs can point towards dehydration.
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Serum osmolality might be increased,
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the blood is more concentrated.
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Hematocrit might be high, again,
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because the blood cells are concentrated
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in less plasma volume.
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BUN, blood urea, nitrogen, often goes up.
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Serum sodium can be high, low, or normal,
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depending on the type of dehydration,
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which is why understanding those types is key.
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- Right, connects back to the types.
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- Exactly, and urine-specific gravity
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will usually be elevated.
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The urine is more concentrated
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because the kidneys are trying desperately
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to hold onto water.
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- Okay, that's a really comprehensive assessment picture.
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extremely helpful.
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So we've identified the problem using these signs.
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What are the core nursing interventions?
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What do we do?
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- Well, the main goals are,
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one, keep monitoring everything closely,
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two, stop any further fluid loss if possible,
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and three, replace the loss fluid safely.
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- Monitor, prevent loss, replace fluid.
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- Precisely.
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So ongoing assessment is key.
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Keep checking those cardiovascular signs,
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respiratory status, neuro checks,
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I know skin checks, GI status, watch the trends.
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- Constant vigil.
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- Absolutely.
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Then for replacement, if the patient can drink,
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oral rehydration is usually the first choice.
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Small sips frequently.
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Oral rehydration solutions often contain electrolytes too,
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which is ideal.
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- Oral first, if possible.
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- Yes, but if they can't drink or the deficit is severe,
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then IV fluids are necessary.
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- IV therapy.
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- And with IVs or even with oral intake,
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strict monitoring of intake and output is just critical.
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you need to know exactly what's going in
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and what's coming out to guide the therapy
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and avoid overload.
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- Makes sense.
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Does the type of IV fluid matter
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based on the type of dehydration?
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- Yes, very much so.
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It's not one size fits all.
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For isotonic dehydration,
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you generally give isotonic fluids,
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like normal saline,.9% sodium chloride,
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or lactated ringers.
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They match the body's normal concentration.
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- Okay, isotonic for isotonic.
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- Right.
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For hypertonic dehydration, where the cells are shrunk,
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you need to give a hypotonic solution,
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like half normal saline, 0.45% sodium chloride.
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This helps gently rehydrate the cells.
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- Hypotonic fluids for hypertonic dehydration.
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- Correct, and for hypertonic dehydration
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where the cells are swollen and plasma volume is low,
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you might need a hypertonic solution, like 3% saline.
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This helps pull fluid back into the vascular space.
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But hypertonic solutions have to be given really carefully,
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usually in an ICU setting, with close monitoring,
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because they can cause rapid fluid shifts or fluid overload.
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- High risk, needs close watch.
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- Yeah. - Got it.
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Are there other treatments involved
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besides fluids, medications?
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- Often, yes.
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You need to treat the underlying cause, right?
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So if it's diarrhea, maybe anti-diarrheals,
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if it's vomiting and emetics.
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- Treat to cause?
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- Infection, antimicrobials, fever, antibiotics.
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If their oxygen saturation is low
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because of poor perfusion,
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they might need supplemental oxygen.
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- Okay.
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- And you absolutely have to monitor electrolytes closely,
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sodium, potassium, et cetera, and be
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ready to replace those or correct imbalances as ordered.
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Right.
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Electrolyte management is key too.
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Crucial part of it.
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This has been incredibly clear.
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Thank you.
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Let me try and do a quick recap, especially for everyone
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listening who's got the NCLEX in their sites.
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So we talked about fluid volume deficit, dehydration.
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Remember, there are three main types
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based on what's lost relative to water--
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isotonic, equal loss, hypertonic, more water loss,
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cell shrink, and hypotonic, more electrolyte loss,
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cell swell. Knowing the assessment findings is vital. Think thready pulse, low BP, orthostatics,
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poor turgor, low urine output, altered mental status, and specific lab changes like osmolality,
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hematocrit, BUN, specific gravity. It's a good summary. And interventions focus on
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monitoring closely, stopping a loss, and replacing fluids orally if possible, or IV fluids matched
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to the type of dehydration. Isotonic for isotonic, hypertonic for hypertonic, hypertonic for
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or hypotonic carefully.
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Plus, treating the cause and managing electrolytes.
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- Exactly.
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- Understanding this whole picture isn't just exam prep,
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it's fundamental to keeping patients safe.
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- Couldn't agree more, it's core nursing knowledge.
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- Well, thank you so much for breaking all that down
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for us today, really appreciate your expertise and insights.
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- My pleasure, happy to help clarify it.
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- And for all of you listening,
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we hope this deep dive has solidified your understanding
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of fluid volume deficit.
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Join us next time as we tackle
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another essential nursing concept right here
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on MedSimu Nursing
