⚡ Electrolyte Imbalances: The Complete NCLEX Cheat Sheet
Electrolyte imbalances are NCLEX favorites. Here's a complete breakdown of the big 4 — what to watch for and what to do:
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🔵 POTASSIUM (K+) — Normal: 3.5 – 5.0 mEq/L
Hypokalemia (< 3.5):
• Causes: Diuretics (furosemide), vomiting, diarrhea, NG suction
• Signs: Muscle weakness, leg cramps, shallow respirations, decreased bowel sounds, U waves on ECG
• Nursing: Give K+ supplements (NEVER IV push — always dilute), monitor ECG, encourage potassium-rich foods (bananas, oranges, potatoes, spinach)
Hyperkalemia (> 5.0):
• Causes: Renal failure, ACE inhibitors, K-sparing diuretics, tissue destruction
• Signs: Muscle twitching → weakness, bradycardia, tall peaked T waves, risk of cardiac arrest
• Nursing: Calcium gluconate (cardiac stabilizer), insulin + glucose (drives K+ into cells), kayexalate, restrict K+ foods, prepare for dialysis
Memory trick: "The HEART doesn't like high K+" — think cardiac arrest risk
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🟡 SODIUM (Na+) — Normal: 136 – 145 mEq/L
Hyponatremia (< 136):
• Causes: SIADH, water intoxication, diuretics, heart failure
• Signs: Confusion, headache, nausea, seizures, muscle cramps
• Nursing: Restrict fluids, give hypertonic saline (3% NaCl) SLOWLY, monitor for cerebral edema, seizure precautions
Hypernatremia (> 145):
• Causes: Dehydration, diabetes insipidus, excess sodium intake
• Signs: Thirst, dry mucous membranes, restlessness, confusion, elevated temperature
• Nursing: Give hypotonic fluids (0.45% NaCl), encourage water intake, monitor I&O, daily weights
Memory trick: "Water follows salt" — where sodium goes, water follows
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🟢 CALCIUM (Ca²+) — Normal: 9.0 – 10.5 mg/dL
Hypocalcemia (< 9.0):
• Causes: Thyroidectomy (parathyroid damage), pancreatitis, vitamin D deficiency, renal failure
• Signs: Numbness/tingling, muscle spasms, positive Chvostek's sign (face twitch), positive Trousseau's sign (hand spasm), seizures, prolonged QT
• Nursing: Give IV calcium gluconate, seizure precautions, vitamin D supplement
Hypercalcemia (> 10.5):
• Causes: Hyperparathyroidism, cancer, prolonged immobility, excess vitamin D
• Signs: Muscle weakness, constipation, kidney stones, confusion, shortened QT, cardiac arrest risk
• Nursing: Hydrate aggressively (NS), loop diuretics (furosemide — flushes calcium), weight-bearing exercise, limit calcium/vitamin D intake
Memory trick: Chvostek's = Cheek (tap face), Trousseau's = Tourniquet (BP cuff)
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🔴 MAGNESIUM (Mg²+) — Normal: 1.3 – 2.1 mEq/L
Hypomagnesemia (< 1.3):
• Causes: Alcoholism, malnutrition, diuretics, diarrhea
• Signs: Tremors, hyperactive reflexes, seizures, cardiac dysrhythmias (similar to hypokalemia)
• Nursing: Give magnesium sulfate IV (slowly — watch for decreased reflexes/respiratory depression), increase dietary Mg (nuts, whole grains, green leafy vegetables)
Hypermagnesemia (> 2.1):
• Causes: Renal failure, excess Mg intake (antacids), MgSO4 overdose
• Signs: Decreased deep tendon reflexes (FIRST sign), drowsiness, hypotension, respiratory depression, cardiac arrest
• Nursing: Stop Mg administration, give calcium gluconate (antidote), mechanical ventilation if needed
Memory trick: Always check reflexes before giving MgSO4 — lost reflexes = STOP
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NCLEX Tip: When you see an electrolyte question, go straight to the cardiac effects. The NCLEX loves testing ECG changes and life-threatening complications.
Which electrolyte trips you up the most? Let's review it 👇
