Harvey's Garden

Hypokalemia

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2 min read

Epidemiology

Etiology

  • Decreased intake
  • Intracellular translocation
    • Insulin (eg, treatment of DKA, refeeding syndrome)
    • β-adrenergic activity
      • Pharmacologic (eg, albuterol, dobutamine)
      • Stress-induced (eg, alcohol withdrawal, acute MI)
        • Catecholamine (eg, norepinephrine, epinephrine) release. Epinephrine activates the beta-2 receptor, leading to increased activity of the sodium-potassium ATPase pump and the sodium-potassium-2-chloride cotransporter, both of which transport potassium intracellularly.
    • Alkalosis (respiratory or metabolic)
    • ↑ Cell reproduction (eg, acute myeloid leukemia, GM-CSF)
  • Gastrointestinal loss
  • Urinary loss
  • Sweat loss
    • Extreme exercise in hot climate
  • Hypomagnesemia: Co-existing deficiency that causes refractory hypokalemia due to loss of inhibition on renal outer medullary potassium (ROMK) channels, leading to excessive renal K+ wasting. c
    • Over 50% of patients with clinically significant hypokalemia have concomitant magnesium deficiency

Pathophysiology

  • ↑ Extracellular K+ concentration → resting membrane potential becomes less negative than -90 mV → ↑ excitability

Clinical features

Diagnostics

Treatment

  1. Correct Hypomagnesemia: Replete Mg2+ first (or concurrently); potassium repletion will fail if magnesium remains low. c
  2. Oral Potassium Replacement: First-line for mild-to-moderate asymptomatic hypokalemia (K+ 2.5–3.5 mEq/L). Potassium chloride (KCl) is preferred.
  3. IV Potassium Replacement: Indicated for severe hypokalemia (< 2.5 mEq/L), symptomatic pts, or those with EKG changes.
    • Max infusion rate via peripheral IV: 10 mEq/hr (to avoid local burning and phlebitis).
    • Max infusion rate via central venous catheter: 20 mEq/hr (requires continuous EKG monitoring).
    • Note: Avoid dextrose-containing carrier fluids (stimulates insulin release, worsening hypokalemia).
  4. Refractory/Underlying Etiology: Discontinue offending drugs (e.g., loop diuretics), prescribe potassium-sparing diuretics (e.g., spironolactone) if diuretic therapy is mandatory, and treat underlying GI/renal losses.

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