NCLEX Deck

Fluid & Electrolytes
& Acid-Base

Clinical study booklet · 17 cards

Contents

Fluid Volume Deficit.

Fluids
What is Fluid Volume Deficit?
  • Loss of extracellular fluid — not enough circulating volume.
  • Reduced perfusion to tissues and organs.
What are the Causes / Risk Factors?
  • Hemorrhage / trauma
  • Vomiting & diarrhea
  • Diuretics, polyuria
  • Poor oral intake
  • Fever & diaphoresis
  • Third-spacing (burns, ascites)
What are the Symptoms?
  • ↑HR, ↓BP, orthostatic hypotension
  • Weak, thready pulse
  • Poor skin turgor, dry mucous membranes
  • ↓urine output, dark urine
  • Weight loss, thirst, restlessness
How is it Diagnosed?
  • ↑Hct, ↑BUN
  • ↑urine specific gravity
  • ↑serum osmolality
  • Daily weight ↓ (1 kg ≈ 1 L)
What is the Treatment?
  • Replace fluids — oral or IV isotonic (0.9% NS, LR)
  • Monitor I&O and daily weight
  • Treat the cause
  • Fall precautions; monitor VS & LOC
NCLEX TipDaily weight is the most reliable indicator of fluid loss — 1 kg ≈ 1 L.
© NCLEX Deck1 / 17

Fluid Volume Excess.

Fluids
What is Fluid Volume Excess?
  • Too much fluid in the vascular & interstitial space.
  • Usually Na⁺ and water retention.
What are the Causes / Risk Factors?
  • Heart failure
  • Renal failure
  • Excess Na⁺ / IV fluids
  • SIADH
  • Cirrhosis
  • Corticosteroids
What are the Symptoms?
  • Edema, rapid weight gain
  • Crackles, dyspnea
  • JVD, bounding pulse
  • ↑BP, S3 gallop
  • Ascites
How is it Diagnosed?
  • ↓Hct & BUN (dilutional)
  • ↓serum osmolality
  • CXR: pulmonary congestion
  • Daily weight ↑
What is the Treatment?
  • Restrict fluids & sodium
  • Loop diuretics
  • Daily weight, strict I&O
  • Semi-Fowler's; O₂ as needed
NCLEX TipCrackles + JVD + rapid weight gain = overload. Weigh daily, same time & scale.
© NCLEX Deck2 / 17

Hyponatremia.

Sodium
What is Hyponatremia?
  • Serum Na⁺ < 135 mEq/L.
  • Water excess dilutes sodium → cells swell (cerebral edema risk).
What are the Causes / Risk Factors?
  • SIADH
  • Excess water intake
  • Diuretics
  • Vomiting / diarrhea
  • Renal disease
  • Adrenal insufficiency
What are the Symptoms?
  • Headache, confusion
  • Muscle cramps & weakness
  • Nausea, vomiting
  • Seizures, ↓LOC (severe)
How is it Diagnosed?
  • Serum Na⁺ < 135
  • Serum & urine osmolality
  • Assess fluid volume status
What is the Treatment?
  • Identify & treat cause
  • Fluid restriction (if dilutional)
  • Hypertonic 3% NS for severe — SLOWLY
  • Seizure precautions
NCLEX TipCorrect sodium slowly — rapid correction risks osmotic demyelination.
© NCLEX Deck3 / 17

Hypernatremia.

Sodium
What is Hypernatremia?
  • Serum Na⁺ > 145 mEq/L.
  • Usually a water deficit; cells shrink.
What are the Causes / Risk Factors?
  • Water deprivation / NPO
  • Diabetes insipidus
  • Excess Na⁺ intake
  • Fever, heat, diaphoresis
  • Osmotic diuresis
What are the Symptoms?
  • Intense thirst, dry mucous membranes
  • Restlessness, agitation
  • Weakness
  • Seizures, coma (severe)
How is it Diagnosed?
  • Serum Na⁺ > 145
  • ↑serum osmolality
  • Urine specific gravity (DI vs dehydration)
What is the Treatment?
  • Replace water — oral or hypotonic IV (0.45% NS) slowly
  • Restrict sodium
  • Monitor neuro status
  • Treat DI
NCLEX TipThink 'salty & dry' — thirst and agitation dominate. Lower Na⁺ gradually.
© NCLEX Deck4 / 17

Hypokalemia.

Potassium
What is Hypokalemia?
  • Serum K⁺ < 3.5 mEq/L.
  • Impairs muscle and cardiac cell function.
What are the Causes / Risk Factors?
  • Loop / thiazide diuretics
  • Vomiting, diarrhea, NG suction
  • Insulin / alkalosis (shift)
  • Corticosteroids
  • Poor intake
What are the Symptoms?
  • Muscle weakness, leg cramps
  • ↓reflexes
  • Paralytic ileus (↓bowel sounds)
  • Flat/inverted T waves, U waves
  • Dysrhythmias
How is it Diagnosed?
  • Serum K⁺ < 3.5
  • ECG: flat T, U wave, ST depression
  • Check magnesium (often low too)
What is the Treatment?
  • Replace K⁺ — oral or diluted IV
  • NEVER IV push; ≤10 mEq/hr peripheral, on a pump
  • Ensure urine output first
  • Cardiac monitoring
NCLEX TipNever give IV potassium by push — always dilute and infuse slowly on a pump.
© NCLEX Deck5 / 17

Hyperkalemia.

Potassium
What is Hyperkalemia?
  • Serum K⁺ > 5.0 mEq/L.
  • Disrupts electrical activity of cardiac & muscle cells — life-threatening.
What are the Causes / Risk Factors?
  • Kidney failure (↓excretion)
  • Metabolic acidosis / DKA
  • Potassium-sparing diuretics
  • Tissue breakdown (burns, crush)
  • ACE inhibitors & ARBs
  • Excess K⁺ / salt substitutes
What are the Symptoms? (Think MURDER)
  • M Muscle weakness / cramps
  • U Urine output low (oliguria)
  • R Respiratory distress
  • D Decreased cardiac contractility
  • E EKG changes (peaked T, wide QRS)
  • R Reflex changes / paresthesias
  • Palpitations & bradycardia
  • Dysrhythmias → cardiac arrest
  • Tingling / numbness
  • Nausea, diarrhea
How is it Diagnosed?
  • Serum K⁺ > 5.0 mEq/L
  • ECG: peaked T, wide QRS
  • ABG (check acidosis)
  • BUN / creatinine
What is the Treatment?
  • Calcium gluconate — protects heart
  • Insulin + D50 — shifts K⁺ into cells
  • Albuterol (nebulized)
  • Kayexalate / patiromer — removes K⁺
  • Dialysis (severe / renal failure)
NCLEX TipPeaked T = hyper (Points up = Plus). Calcium gluconate protects the heart first.
© NCLEX Deck6 / 17

Hypocalcemia.

Calcium
What is Hypocalcemia?
  • Serum Ca²⁺ < 9 mg/dL (ionized < 4.5).
  • Increased neuromuscular excitability → tetany.
What are the Causes / Risk Factors?
  • Hypoparathyroidism / thyroidectomy
  • Vitamin D deficiency
  • Acute pancreatitis
  • Renal failure
  • Massive transfusion (citrate)
What are the Symptoms?
  • +Chvostek's & +Trousseau's signs
  • Tetany, muscle spasms
  • Perioral & finger paresthesias
  • Hyperactive reflexes
  • Laryngospasm, seizures
How is it Diagnosed?
  • Serum & ionized Ca²⁺ low
  • ECG: prolonged QT
  • Check albumin, Mg, phosphorus
What is the Treatment?
  • Calcium (oral or IV calcium gluconate)
  • Vitamin D
  • Seizure & airway precautions
  • Quiet environment
NCLEX TipChvostek's (cheek tap) and Trousseau's (BP-cuff spasm) = low-calcium tetany.
© NCLEX Deck7 / 17

Hypercalcemia.

Calcium
What is Hypercalcemia?
  • Serum Ca²⁺ > 10.5 mg/dL.
  • Decreased neuromuscular excitability — everything slows.
What are the Causes / Risk Factors?
  • Hyperparathyroidism
  • Malignancy (bone metastasis)
  • Prolonged immobility
  • Excess vitamin D / calcium
  • Thiazide diuretics
What are the Symptoms?
  • 'Bones, stones, groans, moans'
  • Muscle weakness, ↓reflexes
  • Kidney stones
  • Constipation, anorexia
  • Confusion, lethargy, dysrhythmias
How is it Diagnosed?
  • Serum Ca²⁺ > 10.5
  • ECG: short QT
  • PTH, renal & bone workup
What is the Treatment?
  • IV NS hydration + loop diuretics
  • Promote mobility & weight-bearing
  • Bisphosphonates, calcitonin
  • Treat underlying cause
NCLEX TipHigh calcium = sluggish everything — slowed muscles, gut, and reflexes.
© NCLEX Deck8 / 17

Hypomagnesemia.

Magnesium
What is Hypomagnesemia?
  • Serum Mg²⁺ < 1.5 mEq/L.
  • Behaves like low calcium — hyperexcitable.
What are the Causes / Risk Factors?
  • Chronic alcohol use
  • Malnutrition / malabsorption
  • Diarrhea
  • Diuretics
  • Often with ↓K⁺ and ↓Ca²⁺
What are the Symptoms?
  • Tremors, twitching
  • Hyperactive reflexes
  • +Chvostek's / Trousseau's
  • Torsades de pointes
  • Seizures, confusion
How is it Diagnosed?
  • Serum Mg²⁺ < 1.5
  • ECG: prolonged QT, torsades
  • Check K⁺ and Ca²⁺
What is the Treatment?
  • Replace magnesium (oral or IV)
  • IV Mg: monitor reflexes & respirations
  • Cardiac monitoring
  • Correct K⁺ / Ca²⁺
NCLEX TipLow Mg mimics low Ca (hyperreflexia, tetany) and is common in alcohol use disorder.
© NCLEX Deck9 / 17

Hypermagnesemia.

Magnesium
What is Hypermagnesemia?
  • Serum Mg²⁺ > 2.5 mEq/L.
  • Depresses neuromuscular and cardiac function.
What are the Causes / Risk Factors?
  • Renal failure
  • Excess Mg antacids / laxatives
  • OB magnesium sulfate therapy
  • Adrenal insufficiency
What are the Symptoms?
  • ↓deep tendon reflexes (early warning)
  • Hypotension, flushing, warmth
  • Bradycardia
  • Respiratory depression
  • Lethargy → cardiac arrest
How is it Diagnosed?
  • Serum Mg²⁺ > 2.5
  • ECG: prolonged PR / QRS
  • Monitor reflexes & RR
What is the Treatment?
  • Stop the magnesium source
  • Calcium gluconate (antidote)
  • IV fluids + loop diuretics
  • Dialysis (renal); support airway
NCLEX TipDisappearing deep-tendon reflexes are the earliest warning of Mg toxicity.
© NCLEX Deck10 / 17

Phosphorus Imbalance.

Phosphorus
What is Phosphorus Imbalance?
  • Normal phosphorus 3.0–4.5 mg/dL.
  • Phosphorus is INVERSELY related to calcium.
What are the Causes / Risk Factors?
  • High: renal failure, tumor lysis, hypoparathyroidism
  • Low: refeeding syndrome, alcohol use, antacids, DKA recovery
What are the Symptoms?
  • Hyperphosphatemia → mirrors HYPOcalcemia (tetany, cramps)
  • Hypophosphatemia → weakness, confusion, ↓cardiac output, bone pain
How is it Diagnosed?
  • Serum phosphorus
  • Serum calcium (moves opposite)
  • Renal function
What is the Treatment?
  • High: phosphate binders, low-phosphorus diet, treat renal cause
  • Low: replace phosphorus; monitor during refeeding
NCLEX TipCalcium up → phosphorus down, and vice versa. They see-saw.
© NCLEX Deck11 / 17

Respiratory Acidosis.

Acid-Base
What is Respiratory Acidosis?
  • pH < 7.35 with PaCO₂ > 45.
  • CO₂ retained from hypoventilation → acid builds up.
What are the Causes / Risk Factors?
  • COPD, asthma
  • Opioid / sedative overdose
  • Atelectasis, pneumonia
  • Chest trauma, muscle weakness
  • Airway obstruction
What are the Symptoms?
  • Dyspnea, ↓/shallow RR
  • Drowsiness, headache
  • Confusion, ↓LOC
  • Tachycardia, dysrhythmias
  • Flushed skin
How is it Diagnosed?
  • ABG: pH ↓, PaCO₂ ↑ (HCO₃ ↑ if compensating)
  • Pulse oximetry
What is the Treatment?
  • Improve ventilation & airway
  • Reverse cause (e.g., naloxone)
  • Bronchodilators; cautious O₂ in COPD
  • Deep breathing / suction
NCLEX TipNot breathing enough traps CO₂ → acidosis. Fix ventilation first (ABCs).
© NCLEX Deck12 / 17

Respiratory Alkalosis.

Acid-Base
What is Respiratory Alkalosis?
  • pH > 7.45 with PaCO₂ < 35.
  • Hyperventilation blows off too much CO₂.
What are the Causes / Risk Factors?
  • Anxiety / panic
  • Pain, fever
  • Hypoxia, high altitude
  • Pulmonary embolism
  • Over-aggressive mechanical ventilation
What are the Symptoms?
  • Lightheadedness, dizziness
  • Tingling / paresthesias
  • Carpopedal spasm
  • Palpitations
  • Rapid deep breathing
How is it Diagnosed?
  • ABG: pH ↑, PaCO₂ ↓ (HCO₃ ↓ if compensating)
What is the Treatment?
  • Treat cause — calm anxiety, control pain
  • Coach slow breathing
  • Correct hypoxia
  • Adjust ventilator settings
NCLEX TipHyperventilation blows off CO₂ → alkalosis. Address the anxiety or pain.
© NCLEX Deck13 / 17

Metabolic Acidosis.

Acid-Base
What is Metabolic Acidosis?
  • pH < 7.35 with HCO₃ < 22.
  • Acid gain or bicarbonate loss.
What are the Causes / Risk Factors?
  • DKA / ketoacidosis
  • Lactic acidosis / shock
  • Renal failure
  • Severe diarrhea (loses bicarb)
  • Salicylate toxicity
What are the Symptoms?
  • Kussmaul respirations (deep, rapid)
  • Confusion, lethargy
  • Hyperkalemia
  • Hypotension, warm skin
  • Nausea
How is it Diagnosed?
  • ABG: pH ↓, HCO₃ ↓ (PaCO₂ ↓ if compensating)
  • Anion gap
  • Check K⁺, glucose, lactate
What is the Treatment?
  • Treat cause (insulin+fluids for DKA; perfusion for shock)
  • Sodium bicarbonate if severe
  • Monitor K⁺ & cardiac rhythm
NCLEX TipDiarrhea loses bicarbonate → metabolic acidosis. DKA is the classic cause.
© NCLEX Deck14 / 17

Metabolic Alkalosis.

Acid-Base
What is Metabolic Alkalosis?
  • pH > 7.45 with HCO₃ > 26.
  • Acid loss or bicarbonate gain.
What are the Causes / Risk Factors?
  • Vomiting / NG suction (loses acid)
  • Excess antacids / bicarbonate
  • Diuretics (loss of K⁺, Cl⁻)
  • Hypokalemia
  • Hyperaldosteronism / Cushing's
What are the Symptoms?
  • Slow, shallow breathing (compensation)
  • Dizziness, confusion
  • Tingling, tremors, cramps
  • Tetany (with ↓Ca²⁺)
  • Hypokalemia signs
How is it Diagnosed?
  • ABG: pH ↑, HCO₃ ↑ (PaCO₂ ↑ if compensating)
  • Check K⁺ and Cl⁻
What is the Treatment?
  • Treat cause; restore fluids (0.9% NS)
  • Replace K⁺ and Cl⁻
  • Monitor for tetany & dysrhythmias
NCLEX TipVomiting or NG suction loses acid → metabolic alkalosis. Replace K⁺ and Cl⁻.
© NCLEX Deck15 / 17

ABG Interpretation (ROME).

Acid-Base
Normal Values
  • pH 7.35–7.45
  • PaCO₂ 35–45 mmHg (respiratory)
  • HCO₃ 22–26 mEq/L (metabolic)
  • PaO₂ 80–100 mmHg
The ROME Rule
  • Respiratory OPPOSITE — pH & CO₂ move in opposite directions
  • Metabolic EQUAL — pH & HCO₃ move in the same direction
Step-by-Step
  • 1. pH: < 7.35 acidosis, > 7.45 alkalosis
  • 2. Which value matches the pH? CO₂ (respiratory) or HCO₃ (metabolic)
  • 3. Compensating? The other value shifts toward normalizing pH
NCLEX TipMatch the pH to CO₂ or HCO₃ to name the primary problem, then check for compensation.
© NCLEX Deck16 / 17

IV Fluid Tonicity.

IV Fluids
Isotonic — 0.9% NS, LR
  • Stays in the vessels; expands intravascular volume
  • Use: shock, hypovolemia, blood loss, DKA (NS)
Hypotonic — 0.45% NS
  • Shifts water INTO the cells
  • Use: cellular dehydration, hypernatremia
  • Caution: avoid with ↑ICP / cerebral edema risk
Hypertonic — 3% NS, D10, D5NS
  • Pulls fluid OUT of cells into the vessels
  • Use: severe hyponatremia, cerebral edema
  • Give slowly — watch for fluid overload
NCLEX TipIsotonic stays put; hypotonic moves INTO cells; hypertonic pulls fluid OUT of cells.
© NCLEX Deck17 / 17
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