Understanding Fluid and Electrolyte Imbalances for NCLEX: The Ultimate Study Guide

Why Fluid and Electrolytes Are NCLEX Gold

Fluid and electrolyte imbalances are one of the most heavily tested topics on the NCLEX. Questions on this topic appear across all NCLEX categories — from Physiological Integrity to Reduction of Risk Potential.

Sodium (Na+) — Normal: 135-145 mEq/L

Hyponatremia (Na+ below 135)

Causes: Excessive water intake, SIADH, diuretics, heart failure, liver disease. Signs: Headache, confusion, seizures, nausea, muscle weakness. Interventions: Fluid restriction, hypertonic saline (severe cases), seizure precautions.

Hypernatremia (Na+ above 145)

Causes: Dehydration, diabetes insipidus, excessive sodium intake. Signs: Extreme thirst, dry mucous membranes, confusion, seizures. Interventions: Gradual fluid replacement — correct slowly to prevent cerebral edema!

Potassium (K+) — Normal: 3.5-5.0 mEq/L

Potassium is the most critical electrolyte for cardiac function. Both hypo- and hyperkalemia can cause life-threatening arrhythmias.

Hypokalemia (K+ below 3.5)

Causes: Loop diuretics (furosemide), vomiting, diarrhea, insulin therapy. Signs: Muscle weakness, leg cramps, U waves on EKG. Key Nursing Note: IV potassium must NEVER be given as a bolus — always diluted infusion!

Hyperkalemia (K+ above 5.0)

Causes: Renal failure, potassium-sparing diuretics, tissue destruction. Signs: Peaked T waves on EKG, bradycardia, cardiac arrest. Interventions: Kayexalate, IV calcium gluconate (cardiac protection), insulin + dextrose.

Calcium (Ca2+) — Normal: 8.5-10.5 mg/dL

Hypocalcemia

Signs: Trousseau's sign (carpal spasm with BP cuff), Chvostek's sign (facial twitch with tapping), tetany, seizures. Interventions: IV calcium gluconate, fall and seizure precautions.

Hypercalcemia

Remember: Bones, Stones, Groans, Psychic Moans — bone pain, kidney stones, constipation, depression/confusion.

Magnesium (Mg2+) — Normal: 1.5-2.5 mEq/L

Hypermagnesemia Key Sign: Loss of deep tendon reflexes (DTRs) is the first sign of toxicity. Antidote = calcium gluconate. This is critically important in preeclampsia management with magnesium sulfate!