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Hypokalemia Differential Diagnoses

Normal Reference Range for Serum Potassium:  3.5 to 5.5 mEq/L

    • Associations:  pH > 7.45 +/- elevated bicarbonate (HCO3-)
    • Pathophysiology:  The body responds to shifts in acid-base balance by moving H+ ions out of the cell, resulting in K+ ions moving into the cell. 
    Amphotericin B Toxicity
    • Associations:  Low serum Mg++ +/- evidence of nephrotoxicity (elevated serum creatinine)
    • Pathophysiology:  Damages the cell membranes by creating pores in the luminal cells of the nephron decreasing their ability to regulate Mg++ and K+ reabsorption.
    Bartter Syndrome
    • Associations:  Hypochloremic metabolic alkalosis
    • Pathophysiology:  A defect in chloride transport at the thick ascending loop of Henle resulting in Cl- and K+ loss and metabolic alkalosis.
    Beta Agonist Excess
    • Associations:  Continuous nebulized albuterol for asthma or COPD exacerbation or as a therapy for hyperkalemia
    • Pathophysiology:  Beta-receptor agonists (e.g., albuterol) causes a shift of K+ into the cells by increasing the activity of Na+/K+ ATPase pump.
    Bicarbonate Use
    • Associations:  Patients being given bicarbonate for treatment of hyperkalemia or tricyclic antidepressant overdose or severe rhabdomyolysis
    • Pathophysiology:  Increased blood pH causes cells to shift H+ ions out of the cells, resulting in the movement of K+ ions into the cell.
    • Association:  Presence of severe fungal infection +/- hypocalcemia
    • Pathophysiology:  Chelates with cations, especially Ca++ and Mg++ which can cause seizures and cardiac dysrhythmias.
    Gitelman Syndrome
    • Associations:  Low urine Ca++ levels + hypochloremic metabolic alkalosis.
    • Pathophysiology:  Renal salt wasting due to a defect in thiazide Na+/Cl- co-transporter in the distal convoluted tubule.
    Hypokalemia Periodic Paralysis
    • Associations: Intermittent episodes of paralysis + positive family history of this condition
    • Pathophysiology: Autosomal dominant problem with excessive renal and GI losses of K+ decreasing the ability of the nerve to depolarize.
    • Associations:  Elevated blood pressure +/- moon facies or edema +/- hypernatremia
    • Pathophysiology:  Excess mineralocorticoid activity of aldosterone results in the unbalanced reabsorption of Na+ and water and release of K+ in the distal collecting tubule of the nephron.
    • Associations: Dietary or nutritional deficiency +/- alcoholic
    • Pathophysiology:  Prevents K+ repletion and maintenance of K+ because the Na+/K+ ATPase pump uses Mg++ as a co-factor for function.
    Insulin Excess
    • Associations:  Iatrogenic due to treatment of diabetes or hyperkalemia or Munchausen syndrome
    • Pathophysiology:   Insulin causes K+ to shift into the cell via activation of the Na+/K+ ATPase pump which causes 2 K+ ions to move into the cell and 2 Na+ cations to move out of the cell.
    Liddle's Syndrome
    • Associations:   High blood pressure +/- resistant to typical treatment
    • Pathophysiology:  Mutation in SCNN1B and SCNN1G genes resulting in epithelial Na+ channels that do not get degraded and cause excessive Na+ reabsorption & loss of K+.
    Loop Diuretics (Bumetanide, Furosemide, Torsemide)
    • Associations:  Past medical history of heart failure or fluid overload or cirrhosis on high dose spironolactone
    • Pathophysiology:  Inhibits the Na+/K+/Cl- cotransporter in the thick ascending loop of Henle which results in the reduction of paracellular reabsorption of magnesium and calcium.  The net effect is a loss of both K+ and Mg++ from the body.
    Nasogastric Tube
    • Associations:  Nausea and vomiting +/- bowel obstruction where a nasogastric tube is being used for management
    • Pathophysiology:  The parietal cells within the gastric mucosa utilize the K+/H+ ATPase pump to regulate the gastric contents of K+ and H+ ions.  When nasogastric (NG) tubes are being used at low intermittent or continuous suction, there is a loss of both due to removal through the NGT tube.
    Renal Tubular Acidosis - Types 1 & 2
    • Associations:  Hypokalemia + metabolic acidosis
    • Pathophysiology:  Damage to the renal tubule results in impairment in ability to regulate the reabsorption of electrolytes from the urine filtrate.
    • Associations:  Abdominal pain + nausea
    • Pathophysiology:  The parietal cells within the gastric mucosa utilize the K+/H+ ATPase pump to regulate the gastric contents of K+ and H+ ions.  When vomiting occurs, there is a loss of both.