Differential Diagnosis for Hypokalemia

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.

Foscarnet

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.

Hyperaldosteronism

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.

Hypomagnesemia

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.

Vomiting

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.

Hypokalemia Differential Diagnoses