fluid and electrolytes

regulating fluids

shifts between intracellular fluid (ICF) and Extracellular fluid (ECF) for transports of nutrients gases and waste.

capillaries

filter out of vessels that increase hydrostatic pressure

and reabsorb back into vessel, which increases osmotic pressure

kidneys

kidneys are like water filters.

• If you drink a LOT of water, it’s too watery, so your pee comes out clear.

• If you don’t drink enough, your pee is more yellow because it’s more concentrated.

cardiovascular system

is a pump.

• If it pumps faster, it pushes blood harder through your body.

• That makes your blood pressure go up (like blowing harder into a balloon).

Third-spacing

 is when the water leaks out into places it shouldn’t go — like into the walls or basement — where it can’t be used by the house anymore.

Thired spacing: What happens

• Even though your body has water, it’s stuck in the wrong place.

• That means the blood doesn’t have enough fluid, so your heart, kidneys, and blood pressure start to struggle.

signs of thrid spacing

Early sign

• Less pee 🚽 → Even if you drink enough, your kidneys don’t get enough blood, so they make less urine to save water.

 

Other signs

• You look and feel like you don’t have enough fluid in your blood:

  • Faster heartbeat ❤‍🔥 (heart works harder)

  • Lower blood pressure ⬇

  • Swelling (edema) 💧 in your body

  • Weight goes up ⚖ (because fluid is stuck in tissues)

  • Fluids in vs. fluids out don’t match (imbalance)

Third spacing occurs in

• Ascites → fluid in the belly

• Burns 🔥 → skin is damaged, fluid leaks out

• Peritonitis 🦠 → infection in the belly lining

• Bowel obstruction 🚫🥒 → blocked intestines cause fluid shift

• Massive bleeding 🩸

dehydration

when your body loses more water than salt (electrolytes).

How your body tries to fix dehydration (compensatory mechanisms):

• SNS (sympathetic nervous system) = makes you feel thirsty 🥤

• ADH (antidiuretic hormone) = tells kidneys to hold onto water 🚱

• Aldosterone = helps keep both water and salt 💦🧂

why older adults are at risk for dehydration

• They have less body water to start with

• They don’t feel as thirsty as younger people

• Their bodies can’t adjust as quickly

Severe dehydration (fluid volume deficit) dangers

• Your blood becomes too “empty” (low volume of blood)

• Your heart has to work really hard to pump what little fluid is left

• Eventually, your body can’t keep blood pressure up → hypovolemic shock 🚨

• This can even cause seizures or be life-threatening

Recognize and Analyze Cues of Dehydration (Low Fluid Volume)

1. Low volume in the blood (not enough fluid in the pipes 🚰)

• Fast heart rate = tachycardia ❤‍🔥

• Weak, thin pulse = thready pulse

• Low blood pressure = hypotension ⬇

• Fast breathing = tachypnea 😮‍💨

• Little urine = oliguria 🚽

• Slow capillary refill (press nail → takes long to turn pink)

 

2. Low volume to the brain (brain not getting enough fluid 🧠💧)

• Dizziness 🎢

• Fainting (syncope) 😵

• Confusion 🤔

 

3. Low water in tissues (body cells are thirsty 🌵)

• Thirst 🥤

• Dry mouth/mucous membranes 👅

• Nausea & vomiting 🤢

• Skin turgor down = pinch skin, it stays up like a tent ⛺

dehydration risk factors (what causes it)

• Losing too much water (sweat, diarrhea, fever)

• Third spacing = fluid stuck in wrong place (burns, ascites)

• Blood or plasma loss (hemorrhage)

• Not taking in enough (NPO, can’t swallow, anorexia)

Lab test for dehydration

• Hematocrit (Hct) = high (unless bleeding, then low)

• Blood osmolality = high (blood is concentrated)

• Urine specific gravity = high (pee is dark & concentrated)

• Sodium (Na+) = high

• BUN = high (>25, blood too concentrated

deydration immediate actions

1. Check vital signs & labs

   • Breathing: rate & effort (RR) 😮‍💨

   • Oxygen: SpO₂

   • Urine output 🚽

   • Blood tests: CBC, electrolytes 🧪

2. Give oxygen if needed 🫁

3. Check the heart & brain

   • Level of consciousness (LOC) 🧠

   • Heart rhythm ❤

   • Blood pressure lying & standing (orthostatic BP)

4. Rehydrate the body 💦

   • Oral fluids if possible 🥤

   • IV fluids if ordered 💉

   • Keep IV access ready

dehydration ongoing actions

1. Track fluid balance

   • Daily weight ⚖

   • Input & output (I & O)

2. Alert the doctor if urine <30 mL/hr 🚨

3. Watch for nausea & vomiting 🤢

4. Safety first

   • Help with walking / changing positions slowly 🚶‍♂

   • Prevent falls

Hypotonic fluid

0.45% Normal Saline (half-normal)

More water than particles → water moves into cells

Dehydration inside cells; watch for swelling

isotonic fluid

0.9% Normal Saline (NSS), Lactated Ringers

Expands blood volume → stays mostly in blood vessels

Replace fluid loss, maintain IV access

hypertonic fluid

3% NaCl, Mannitol

Pulls water out of cells into blood

Cerebral swelling (brain), very concentrated; use carefully

Dextrose fluid

D5W (5% dextrose in water)

Starts isotonic → becomes hypotonic after glucose is used

Can cause fluid overload; not for nutrition

Hypervolemia

• Your body has too much water or fluid.

• The electrolytes (salts, minerals) are usually still normal, but they get diluted because there’s too much water.

Hypervolemia causes

• Drinking or receiving too much fluid

• Fluid overload from IVs or heart/kidney problems

• Body can’t remove fluid properly (kidney issues)

Hypervolemia complications

• Severe cases → heart and lungs affected

  • CHF (congestive heart failure)

  • Pulmonary edema (fluid in lungs)

hypervolemia body compensation

• Kidneys try to get rid of extra salt and water (natriuresis)

• Less aldosterone is released → body holds onto less water

Hypervolemia Recognize the Cues

Body System	What You Might See
Vitals	Fast heart rate (tachycardia), strong pulse, high blood pressure (HTN), fast breathing
Neuro / Muscles	Confusion, muscle weakness, seizures, tingling, vision changes
GI	More active gut (increased motility), fluid in belly (ascites)
Respiratory	Trouble breathing (dyspnea), crackles in lungs, shortness of breath when lying down (orthopnea)
Other	Swelling (pitting edema), jugular vein distention (JVD), weight gain, pale and cool skin

💧 Hypervolemia risk factors

1. Hypervolemia (too much fluid + sodium)

• Kidney disease 🚽 (can’t get rid of fluid)

• CHF ❤ (heart too weak to pump fluid forward)

• Cirrhosis 🍺 (liver disease → fluid buildup in belly)

• Older age 👵 (less effective heart & kidneys)

• Excessive sodium intake 🧂 (salt pulls in water)

2. Overhydration (too much water, not enough electrolytes)

• Drinking/replacing only water 💧 (no electrolytes)

• SIADH (too much ADH → body keeps water)

• Too much IV D5W or hypotonic fluids

Hypervolemia lab test

• Hematocrit (Hct) ↓ (blood is watered down)

• Blood osmolality ↓ (less concentrated)

• Urine specific gravity ↓ (pee more diluted)

  • Exception: SIADH → urine concentrated

• Sodium (Na⁺) ↓ (too much water makes sodium look low)

• BUN ↓ (blood looks diluted)

• Other electrolytes ↓ in overhydration

• ABG → Respiratory alkalosis (from fast breathing, trying to blow off CO₂)

💧 FVO – Immediate actions

1. Monitor breathing 🫁

   • Respiratory rate & effort

   • Breath sounds (crackles, wheezes)

   • Shortness of breath / dyspnea

   • SpO₂ (oxygen level)

2. Check labs & diagnostics 🧪

   • Urine output

   • CBC, electrolytes

   • ABG

   • Chest X-ray (CXR for pulmonary edema)

3. Interventions

   • Give oxygen as needed

   • Give diuretics (to help pee out excess fluid) 💊

   • Keep IV access ready

   • Restrict fluids & sodium intake 🚫🥤🧂

PVO Ongoing actions

1. Track fluid balance

   • Daily weight ⚖ (best indicator of fluid changes)

   • Input & output (I & O)

2. Protect skin & comfort

   • Reposition every 2 hours (prevent skin breakdown from edema)

   • Monitor for swelling (edema)

   • Elevate/support arms & legs 🛏

3. Safety

   • Monitor for weakness, confusion, or fall risk

   • Ensure safe mobility 🚶‍♂

⚖ Acid-Base Balance (ABG Basics) Why it matters

• Keeps the body in homeostasis (stable internal balance).

• Controlled by lungs (respiratory) and kidneys (metabolic).

• Imbalances → Acidosis (too much acid) or Alkalosis (too much base).

pH

normal range: 7.35-7.45

acid or basic

overall balance

PaCO2

normal range: 35-45

CO2 in blood

respiratory

PaO2

normal range: 80-100

O2 level in aterial blood

respitory gas exchange

HCO3

normal range: 22-26

bicarbonate

metabolic

SaO2

normal range: 95-100%

% of hemoglobin carrying O2

O2 status

Clinicians Use ABG To:

• Check respiratory efficiency (ex: COPD, asthma, respiratory failure)

• Assess metabolic function (ex: kidney disease, diabetes, shock)

• Diagnose/manage acid-base imbalances

• Guide treatments: oxygen therapy, ventilation, electrolyte replacement, meds

Metabolic Acidosis

• ABG Pattern: ↓ pH, ↓ HCO₃⁻

• Risk Factors (Causes):

  • Diarrhea 🚽 (loss of bicarb)

  • Fever 🌡

  • Hypoxia (low O₂)

  • Starvation / ketoacidosis 🍽

  • Seizures ⚡

  • ASA (aspirin) overdose 💊

  • Renal failure 🩺

  • DKA (diabetic ketoacidosis)

  • Dehydration

• Clinical Manifestations (Signs):

  • Bradycardia ❤‍🩹

  • Weak pulses

  • Hypotension ⬇

  • Tachypnea (fast breathing, Kussmaul respirations) 😮‍💨

  • Flaccid paralysis

  • Confusion

Metabolic Alkalosis

• ABG Pattern: ↑ pH, ↑ HCO₃⁻

• Risk Factors (Causes):

  • Too many antacids 🍼

  • GI suction (loss of stomach acid)

  • Hypokalemia (low K⁺)

  • TPN (Total Parenteral Nutrition)

  • Blood transfusions

  • Prolonged vomiting 🤮

• Clinical Manifestations (Signs):

  • Dizziness 🎢

  • Paresthesia (tingling) ✨

  • Muscle cramps/spasms (hypertonic muscles) 💪

  • Slow/shallow breathing (respiratory compensation)

Interventions (Both Metabolic Acidosis & Alkalosis)

• Treat the underlying cause 🩺

• Give fluids + electrolytes as needed 💧🧂

• Monitor vital signs, neuro status, and ABGs

⚖ Compensation for Metabolic Imbalances

1. Metabolic Acidosis (↓ pH, ↓ HCO₃⁻)

• Problem: Too much acid / not enough base

• Compensation:

  • Lungs hyperventilate (breathe fast & deep)

  • This blows off CO₂ (acid)

  • Helps raise pH back toward normal

  • Example: Kussmaul respirations in DKA

 

2. Metabolic Alkalosis (↑ pH, ↑ HCO₃⁻)

• Problem: Too much base / not enough acid

• Compensation:

  • Lungs hypoventilate (slow breathing)

  • This retains CO₂ (acid)

  • Helps lower pH back toward normal

  • Limited by O₂ needs — the body won’t let you stop breathing too much

 Respiratory Acidosis

• ABG Pattern: ↓ pH, ↑ CO₂

• Risk Factors (Causes):

  • Respiratory depression (opioids, anesthesia, trauma)

  • Pneumothorax (collapsed lung)

  • Airway obstruction (asthma, choking, mucus plug)

  • Inadequate ventilation (neuromuscular disease, hypoventilation)

• Clinical Manifestations (Signs):

  • Dizziness, headache

  • Palpitations

  • Muscle twitching

  • Convulsions/seizures

• Interventions:

  • Maintain a patent airway

  • Administer naloxone if opioid-induced

  • Support ventilation (bag-mask, intubation, mechanical ventilation if severe)

  • Give bronchodilators (open airways)

  • Give mucolytics (thin mucus)

Respiratory Alkalosis

• ABG Pattern: ↑ pH, ↓ CO₂

• Risk Factors (Causes):

  • Hyperventilation (anxiety, panic attack)

  • Hypoxemia (low O₂ → breathing too fast)

  • Altitude sickness ⛰

  • Asphyxiation

  • Asthma

  • Pneumonia

• Clinical Manifestations (Signs):

  • Tachypnea (rapid breathing)

  • Anxiety / panic

  • Tetany (muscle spasms)

  • Paresthesia (tingling in hands/feet)

  • Palpitations, chest pain

• Interventions:

  • Regulate oxygen therapy (don’t over-oxygenate)

  • Reduce anxiety (calm environment, meds if needed)

  • Rebreathing techniques (paper bag, rebreather mask → increases CO₂)

 Compensation for Respiratory Imbalances

1. Respiratory Acidosis (↓ pH, ↑ CO₂)

• Problem: Too much acid (CO₂ buildup from hypoventilation).

• Kidney Compensation:

  • Excrete H⁺ (acid) into urine 🚽

  • Retain HCO₃⁻ (bicarbonate, base) in blood

  • Helps raise pH back toward normal

 

2. Respiratory Alkalosis (↑ pH, ↓ CO₂)

• Problem: Too much base (CO₂ blown off from hyperventilation).

• Kidney Compensation:

  • Excrete HCO₃⁻ (base) in urine 🚽

  • Retain H⁺ (acid) in blood

  • Helps lower pH back toward normal

Hypernatremia >145 causes

Fluid deprivation,

enteral feedings without adequate water flushes,

watery diarrhea (dilutional),

diabetes insipidus,

kidney failure,

excessive sodium intake,

dehydration (dilutional),

Hypernatremia >145 clinical manifestations

Restlessness,

weakness,

disorientation,

hallucinations,

thirst,

dry mucous membranes,

flushed skin,

peripheral/pulmonary edema,

increased muscle tone,

increased deep tendon reflexes

Hypernatremia >145 nursing interventions/ medical management

Medical management:

Gradually lowering serum sodium level with infusion of hypotonic solution.

The gradual decrease will prevent cerebral edema. Restrict dietary sodium, diuretics that promote NA+ loss

Nursing Interventions

I & O, safety, offer fluids at regular intervals