Hyperkalemia (plasma potassium concentration > 5.5 mmol/L) is common in animals with inadequate urine excretion, particularly when they are also acidemic (blood pH < 7.2). Affected animals are depressed, with generalized muscle weakness, and might have cardiac abnormalities. Treatment is based on IV and oral fluid therapy to increase urinary excretion and to correct acid-base abnormalities.
Etiology of Hyperkalemia in Ruminants
Hyperkalemia is common in neonatal ruminants that have diarrhea, dehydration, acidemia, and strong ion (metabolic) acidosis. Hyperkalemia often accompanies acidemia, because low blood pH results in intracellular acidosis and leakage of potassium from the intracellular compartment to the extracellular space.
Hyperkalemia is exacerbated in calves that have severe dehydration, because hypovolemia decreases renal blood flow and consequently the glomerular filtration rate, thereby minimizing the animal's ability to excrete potassium.
Hyperkalemia is rare in steers, wethers, and bucks that have obstructive urolithiasis and bladder or urethral rupture, because excess potassium is secreted in adult ruminant saliva, and affected animals have a decrease in potassium intake because of illness. Hyperkalemia can be present in ruminants with exertional rhabdomyolysis resulting from damage to skeletal muscle cells.
Pseudohyperkalemia is an artificial elevation of potassium concentration that is due to the leakage of potassium from RBCs or to hemolysis in inappropriately prepared or stored blood samples.
Clinical Findings and Diagnosis of Hyperkalemia in Ruminants
Depression
Generalized muscle weakness
Bradycardia or other cardiac arrhythmia
Serum or plasma potassium concentration > 5.5 mmol/L
Severe hyperkalemia is usually associated with depression, weakness, lethargy, and cardiac abnormalities, including bradycardia and other arrhythmias with ECG abnormalities (1), particularly when the serum or plasma potassium concentration is > 6.5 mmol/L. Severe cardiotoxic effects are almost always evident when the serum potassium concentration is ≥ 8 mmol/L.
Serum biochemical analysis is required to confirm a diagnosis of hyperkalemia. Treatment can be guided by measurement of serum potassium concentration, as well as measurement of serum sodium, calcium, phosphorus, urea, and creatinine concentrations; measurement of CK and AST activities; and blood gas analysis.
Treatment of Hyperkalemia in Ruminants
IV administration of saline or sodium bicarbonate
Optional IV administration of glucose and insulin
Treatment of the primary condition
Hyperkalemia should initially be treated by IV administration of saline solution (0.9% NaCl) to increase the rate of urine production in dehydrated patients with a patent urinary system. Sodium bicarbonate is administered to correct systemic and intracellular acidosis and is the preferred IV solution for correcting hyperkalemia in patients with acidemia (blood pH < 7.2).
Pearls & Pitfalls
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Urine should be removed from the abdomen of animals that have obstructive urolithiasis and ruptured bladder due to the high potassium content, and urethral patency should be established.
In select cases, administration of 5% glucose (2.2–4.4 mL/kg/h, IV) and regular insulin (0.1 IU/kg, IV or SC) (1), or of 46.2% hypertonic glucose solution (5 mL/kg, IV) (2), has been described to facilitate the correction of hyperkalemia.
The rationale for IV glucose and insulin administration to treat hyperkalemia is that insulin-mediated glucose entry into cells is accompanied by the movement of potassium from the extracellular space to the intracellular compartment. However, serum potassium concentrations do not begin to decrease until at least 20 minutes after the start of IV glucose administration in hyperkalemic diarrheic calves, and 8.4% hypertonic bicarbonate solution (6.4 mL/kg) is more effective at lowering potassium concentrations (2). Therefore, routine provision of glucose with or without insulin seems unnecessary to correct hyperkalemia.
The treatment of hyperkalemia should therefore focus on expanding the plasma volume to assist in renal excretion of potassium, to identify and correct acidemia, and to increase the serum sodium concentration (3).
Key Points
Hyperkalemia (plasma potassium concentration > 5.5 mmol/L) is common in animals with inadequate urinary excretion, particularly when they are also dehydrated and acidemic (blood pH < 7.2).
Hyperkalemia results in depression, generalized muscle weakness, and a variety of electrocardiographic abnormalities.
Treatment should focus on reestablishing urinary potassium excretion by IV administration of isotonic saline (normal blood pH) or isotonic sodium bicarbonate solutions (blood pH < 7.2).
For More Information
Potassium. eClinpath, Cornell University College of Veterinary Medicine.
References
Sweeney RW. Treatment of potassium balance disorders. Vet Clin North Am Food Anim Pract. 1999;15(3):609-617. doi:10.1016/s0749-0720(15)30166-3
Trefz FM, Constable PD, Lorenz I. Effect of intravenous small-volume hypertonic sodium bicarbonate, sodium chloride, and glucose solutions in decreasing plasma potassium concentration in hyperkalemic neonatal calves with diarrhea. J Vet Intern Med. 2017;31(3):907-921. doi:10.1111/jvim.14709
Constable P. Fluid and electrolyte therapy in ruminants. Vet Clin North Am Food Anim Pract. 2003;19(3):557-597. doi:10.1016/s0749-0720(03)00054-9
