Definition
Serum potassium concentration higher than the testing laboratory's upper limit of normal, generally >5.7 mEq/L (mmol/L).
Pathophysiology
- Potassium is primarily intracellular; serum concentrations do not accurately reflect tissue concentrations.
- Hyperkalemia is often associated with cellular injury (e.g., trauma and ischemia) and other causes of translocation of potassium out of the intracellular space (e.g., acidosis).
- Potassium is eliminated in the kidneys and elimination is enhanced by aldosterone; conditions that inhibit renal elimination of potassium will cause hyperkalemia.
Systems Affected
- Cardiovascular-potassium affects cardiac conduction, and changes are reflected on the ECG; as potassium rises, the T waves become tall and spiked with a narrow base, the QRS complexes widen, and the P-R intervals lengthen; the P waves become smaller and wider and, in animals with severe hyperkalemia, disappear (atrial standstill); higher concentrations of potassium cause fusion of the QRS-T, which causes a wide complex idioventricular rhythm followed by ventricular fibrillation or asystole; ECG changes in animals with hyperkalemia vary and are diminished by hypernatremia, hypercalcemia, and alkalosis.
- Nervous-neuromuscular function affected.
Signalment
- Dog and cat
- Pseudohyperkalemia in certain East Asian dog breeds (e.g., Akita, Shiba, Jindo, and Chinese Shar-Pei)
Signs
Historical Findings
- Weakness
- Collapse
- Flaccid paralysis
- Death
Physical Examination Findings
In addition to historical findings, arrhythmias, especially bradyarrhythmias, in some animals.
Causes
- Pseudohyperkalemia-some blood cells (i.e., RBCs [reported in East Asian dog breeds including Akita, Shiba, Jindo, and Chinese Shar-Peisdue to the presence of a Na-K pump in the mature RBC membrane in some animals], platelets, WBCs), contain high concentrations of potassium; if the blood sample is not analyzed or separated promptly, this intracellular potassium is released into the serum, causing the potassium concentration to be artificially high (pseudohyperkalemia).
- Low potassium elimination-anuric or oliguric renal failure; renal hypoperfusion (complete AV block); urinary tract rupture or urethral obstruction; administration of potassium-sparing diuretics, ACE inhibitors, trimethoprim, nonsteroidal anti-inflammatory drugs, or heparin (causing hypoaldosteronism); some gastrointestinal diseases (e.g., salmonellosis, trichuriasis, duodenal perforation).
- Translocation of potassium-acidosis, reperfusion syndrome, thrombolysis in feline aortic thromboembolism, tumor lysis syndrome, muscle injury (trauma, phosphofructokinase deficiency), severe digitalis overdose, infusion of mannitol, and hyperglycemia causing hyperosmolality.
- High potassium intake-oral or parenteral potassium supplements. Potassium bromide toxicosis
- Miscellaneous-pleural effusion and ascites.
Risk Factors
- Fluid therapy with potassium supplementation.
- Parenteral nutrition.
- Administration of potassium-sparing diuretics (e.g., spironolactone) and ACE inhibitors (e.g., enalapril, benazepril), primarily in patients with renal disease.
- Conditions associated with acidosis.
- Trauma.
- Renal disease.
- Lower urinary tract disease in male cats.
- Cystic calculi in male dogs.
- Thrombocytosis and leukemia.
- Akita, Shiba, Jindo, and Chinese Shar-Pei-pseudohyperkalemia. Not all animals within a breed are at risk for pseudohyperkalemia. Approximately 20% of Akitas have the high potassium phenotype.
- Phosphofructokinase deficiency.
