Hypokalemia and Hyperkalemia: Cardiac Risks and Management

Potassium (K⁺) is the primary intracellular cation; its narrow serum range (3.5–5.0 mEq/L) is critical for cardiac and neuromuscular excitability.

Hypokalemia (<3.5 mEq/L)

Cardiac Effects

• ↑ Risk of ventricular arrhythmias (PVCs, VT/VF), especially with digoxin or structural heart disease.
• ECG: ST depression, flattened T waves, prominent U waves, QT prolongation.

Neuromuscular

• Weakness (proximal > distal), cramps, ileus, respiratory failure if severe (<2.5 mEq/L).

Common Causes

Diuretics (loop/thiazide), GI losses (diarrhea, vomiting), alkalosis, hyperaldosteronism, insulin/β-agonist shift.

Hyperkalemia (>5.0 mEq/L)

Cardiac Effects

• Peaked T waves → PR prolongation → QRS widening → sine wave → VF/asystole.
• Can cause sudden cardiac arrest without warning.

Neuromuscular

• Ascending weakness, paresthesias, flaccid paralysis.

Common Causes

CKD/ESRD, ACEi/ARB/K-sparing diuretics, NSAIDs, rhabdomyolysis, tumor lysis, adrenal insufficiency, acidosis.

Emergency Management

• Hyperkalemia with ECG changes: IV calcium gluconate (membrane stabilization) → insulin+glucose, β-agonist, loop diuretic, kayexalate/patiromer, dialysis.
• Hypokalemia with arrhythmia/severe weakness: IV KCl 10–20 mEq/h (central line) with continuous ECG monitoring.