Disorders of Potassium Metabolism

Etiology (Causes):

• Increased Loss: Renal losses (polyuria, tubular disease), GI losses (vomiting, diarrhea), or iatrogenic loss from large volumes of IV fluid.

• Decreased Uptake: GI stasis or sustained decrease in feed intake.

• Intracellular Shifts: Translocation into cells due to hyperinsulinemia associated with hyperglycemia.

Clinical Findings:

• Mild/Moderate: Often non-specific.

• Severe: Generalized muscle weakness leading to recumbency, ventroflexion of the head, and cardiac arrhythmias (atrial and ventricular premature complexes).

• Chronic: Prolonged, profound deficiency can result in difficult-to-treat myopathy.

Species-Specific Notes:

• Cats: Affected by feline hypokalemic polymyopathy; Burmese cats have an autosomal recessive disorder leading to hypokalemic myopathy.

• Dogs & Cats: Can be caused by hyperaldosteronism.

Primary Causes:

• Reduced Excretion: Inadequate urinary excretion due to hypovolemia, urinary tract obstruction, or bladder rupture.

• Muscle Release: Potassium release into the blood from exertional rhabdomyolysis in horses and ruminants.

• Endocrine: Frequently occurs in dogs with hypoadrenocorticism.

Genetic Factors: Identified as hyperkalemic periodic paralysis in heavily muscled Quarter Horses and related breeds.

Clinical Findings:

• Generalized muscle weakness and depression.

• Cardiac Conduction Disturbances: Can progress to lethal cardiac arrhythmias.

Whole Body Status: Serum concentrations do not always reflect total body status; for example, animals with acidemia may show hyperkalemia despite being whole-body depleted.

Pseudohyperkalemia: Occurs in serum or plasma due to hemolysis, as red blood cells in most species have high potassium concentrations.

Species Variation: Some species possess genetic differences in their erythrocytic potassium concentration, which can affect diagnostic results.