Hyperkalemia

Hyperkalemia is a topic covered in the 5-Minute Emergency Consult.

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Basics

Description

  • Potassium distribution:
    • Extracellular space: 2%
    • Intracellular space: 98%
  • Potassium excretion:
    • Renal: 90%
    • GI: 10%
  • Renal (80–90%) and extrarenal mechanisms maintain normal plasma concentration between 3.5 and 5 mmol/L.
  • Renal excretion of potassium affected by:
    • Dietary intake
    • Distal renal tubular function
    • Acid–base balance
    • Mineralocorticoids
  • Regulation between intracellular and extracellular potassium balance is affected by:
    • Acid–base balance
    • Insulin
    • Mineralocorticoids
    • Catecholamines
    • Osmolarity
    • Drugs

Etiology

  • Decreased potassium excretion:
    • Most common cause: Renal failure (acute or chronic)
    • Distal tubular diseases:
      • Acute interstitial nephritis
      • Renal transplant rejection
      • Sickle cell nephropathy
      • Renal tubular acidosis (diabetes)
    • Mineralocorticoid deficiency:
      • Addison disease
      • Hypoaldosteronism
    • Drugs:
      • ACE inhibitors/angiotensin receptor blockers
      • β-blockers
      • Potassium-sparing diuretics
      • NSAIDs
      • Cyclosporine
      • High-dose trimethoprim
      • Lithium toxicity
  • Intracellular to extracellular potassium shifts:
    • Metabolic acidosis:
      • Serum K+ rises 0.2–1.7 mmol/L for each 0.1 U fall in arterial pH.
    • Hyperosmolar states
    • Insulin deficiency
    • Cell necrosis
    • Rhabdomyolysis
    • Hemolysis
    • Chemotherapy
    • Drugs:
      • Digitalis toxicity
      • Depolarizing muscle relaxants (e.g., succinylcholine)
      • β-blockers
      • α-agonists
    • Hyperkalemic periodic paralysis
  • Excess exogenous potassium load:
    • Cellular breakdown:
      • Trauma
      • Tumor lysis
    • Salt substitutes
    • Oral potassium
    • Potassium penicillin G
    • Rapid transfusions of banked blood
  • Pseudohyperkalemia:
    • Traumatic venipuncture with hemolysis
    • Postvenipuncture release of potassium can occur in the setting of:
      • Thrombocytosis (platelets >800,000/mm3)
      • Extreme leukocytosis (WBC >100,000/mm3)
    • Prolonged tourniquet time

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