Hypokalemia

Clinical Features

• CNS
  • Weakness
  • Cramps
  • Hyporeflexia
• GI
  • Ileus
• Renal
  • Metabolic alkalosis
• CV
  • PACs/PVCs
  • Bradycardia or atrial/junctional tachycardia
  • AV block
  • Ventricular tachycardia, Ventricular fibrillation

Differential Diagnosis

Differential diagnosis of hypokalemia

Shift

• Alkalosis (each 0.10 rise in pH causes 0.5 decrease)
• Insulin
• B-agonist

Decreased intake

• Special diets or those low in potassium

Increased loss

• GI
  • Vomiting, diarrhea, fistula
• Renal
  • Diuretics
  • Hyperaldo
  • Exercise
  • Hypercalcemia
  • Hypomagnesemia

Drugs

• Penicillins
• Lithium
• L-dopa
• Theophyline

Diagnosis

• Serum potassium level is diagnostic
  • Normal = 3.5-5meq/L
  • Severe hypokalemia = <2.5meq/L
• Suggestive ECG findings:
  • ST segment depression
  • U wave (V4-V6)
  • QT prolongation
  • Premature ventricular contraction

Management

• Potassium repletion (PO or IV)
  • Every 10mEq KCl → serum K ↑ ~0.1mEq/L
  • PO preferred (if symptomatic or level is <2.5, both oral and IV should be given)
• Oral potassium
  • Inexpensive and rapidly absorbed
  • KCl tablet (elixir form available but has poor taste)
  • K-Dur (extended release tablet) is large and may be difficult to swallow
• Intravenous potassium
  • Must be given in dilute solutions at slow rate (10meq/hour) to minimize side effects and cardiac toxicity
  • Generally should not give more than 40mEq via IV
  • Side effects: Local tissue burning, phelbitis, sclerosis
• Also treat Hypomagnesemia if present

Disposition

• Based on underlying cause

See Also

• Electrolyte Abnormalities (Main)
• Hypokalemic periodic paralysis
• Hyperkalemia

External Links

• DDxOf: Differential Diagnosis of Electrolyte Abnormalities