Hyperkalaemia

Hyperkalaemia refers to an elevated potassium level in the dog’s blood. The normal range is 3.5–5.5 mmol/l; values above this disrupt the electrical activities of the heart and muscles. Hyperkalaemia is a medical emergency.

Causes of Hyperkalaemia

In dogs, hyperkalaemia usually develops from one of the following causes:

• Kidney failure: The kidneys excrete excess potassium. With impaired kidney function, potassium accumulates in the blood.
• Addison’s disease (hypoadrenocorticism): In this adrenal insufficiency, hormones that regulate potassium and sodium are lacking. The potassium level rises, while the sodium level falls.
• Traumatic injuries: Severe burns, muscle trauma or massive cell breakdown release potassium from the cells into the bloodstream.
• Urinary retention: Urinary tract obstructions (e.g. due to bladder stones) prevent potassium excretion via urine.
• Overdose of potassium-containing medications: Incorrect intravenous administration of potassium can lead to acute hyperkalaemia.

Symptoms of Hyperkalaemia

The clinical picture depends on the severity:

• Weakness and lethargy: A disturbed potassium balance impairs muscle function.
• Muscle weakness or paralysis: In severe cases, this leads to lameness up to paralysis.
• Heart rhythm disturbances: Elevated potassium disrupts the electrical impulses of the heart. Possible consequence: ventricular fibrillation or cardiac arrest.
• Weak, slow pulse: Bradycardia (slow heartbeat) typically occurs with pronounced hyperkalaemia.
• Vomiting and diarrhoea: Gastrointestinal symptoms occur occasionally.

If left untreated, hyperkalaemia can lead to cardiac arrest within a short time.

Diagnosis and Treatment

Diagnosis is made via a blood test (potassium level measurement). Additionally, kidney values (creatinine, urea) are checked, and if Addison’s disease is suspected, the electrolytes sodium and potassium are examined in relation to each other. An ECG shows typical changes: prolonged PR intervals, widened QRS complexes, tall T waves.

Treatment depends on severity and cause:

• Intravenous fluid therapy: Dilutes potassium in the blood and promotes renal excretion.
• Calcium gluconate: Stabilises the heart (membrane potential), but does not lower the potassium level. Emergency measure for life-threatening ECG changes.
• Glucose and insulin: Insulin transports potassium back into the cells; glucose prevents hypoglycaemia.
• Sodium bicarbonate: In metabolic acidosis, it can support the shift of potassium into the cells.

In Addison’s disease, long-term treatment involves mineralocorticoid and glucocorticoid substitution. In kidney failure, dialysis may be necessary.

Prognosis

With timely treatment, the prognosis is good, particularly if an acute cause such as urinary retention is present. With chronic underlying conditions (kidney failure, Addison’s disease), the long-term prognosis depends on the controllability of the underlying condition. Regular blood tests are essential for at-risk patients.