Potassium (K+) on the NCLEX
Hyperkalemia and hypokalemia: ECG changes, causes, emergency treatment.
Potassium 3.5-5.0. The most-tested electrolyte. ECG changes signal severity.
Hyperkalemia (>5)
Causes: renal failure, ACE/ARB, K-sparing diuretics, hemolysis (pseudo), acidosis, tissue breakdown. ECG: peaked T waves → wide QRS → sine wave → cardiac arrest. Treatment: calcium gluconate (cardiac protection, doesn't lower K+) → insulin + D50 (shifts into cells) → albuterol (also shifts) → kayexalate or patiromer (removes) → dialysis (definitive in renal failure).
Hypokalemia (<3.5)
Causes: diuretics (loop, thiazide), vomiting, diarrhea, alkalosis. ECG: flattened T waves, U waves, arrhythmias. Treatment: oral K+ (KCl) if mild. IV K+ if severe (never push, max rate 10-20 mEq/h peripheral, monitor cardiac). Replace magnesium too, low Mg makes K+ replacement ineffective.
Frequently asked
Patient on Lasix with low K+?
Expected. Replace orally if mild, IV if severe. Consider switching to K-sparing or pairing.
Can I IV push KCl?
Never. Always dilute and infuse slowly. Cardiac arrest risk.
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