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Hyperkalemia is the medical term for high levels of potassium in the blood. Potassium is an essential electrolyte (body salt) which performs several functions such as:
- Regulating nerve impulse and muscle contractions.
- Maintains intracellular volume.
- Assists in maintaining blood pressure.
- Maintains heart function.
- Maintains the body's electrolyte balance and acid/alkali levels in cells and tissues.
- It also plays an important role in heart, skeletal, and smooth muscle contraction, making it an important nutrient for normal heart, digestive, and muscular function.
Hyperkalemia occurs due to decreased potassium excretion via the urine. Normal blood values for potassium are 3.5 - 5.8 mmol/L
Decreased urinary excretion are the most common causes of hyperkalemia in cats. It is the role of the kidneys to remove excess potassium from the blood via the urine if they are no longer functioning as efficiently potassium levels can build up.
Other causes can include a shift of potassium from the intracellular fluid into the extracellular fluid (more than 90% of the body's potassium is found within the cells).
- Kidney failure is a common disorder in cats. It may be acute (sudden onset) or chronic (slow and progressive). Chronic kidney failure is seen more commonly in middle-aged to senior cats. There are a number of causes of acute kidney failure such as ingestion of toxins (such as lily or ethylene glycol).
- Urinary tract blockages occur when crystals or stones become lodged in the urethra. Urine is unable to pass the blockage, causing it to build up in the bladder. Once this occurs, the kidneys stop functioning/or become less efficient, and again, blood levels of potassium build up. Males are more prone to developing urinary blockages due to their narrower urethra.
- Ruptured bladders usually occur due to trauma (such as being hit by a car or a fall from a height) or urinary blockage. Fluid leaks into the abdomen, causing a build up of toxic wastes, including potassium. Obviously, once the bladder is ruptured, urine can no longer be excreted from the body, making the problem worse.
- Addison's disease is an endocrine disorder due to a deficiency of corticosteroids, which the adrenal glands produce. One hormone, aldosterone, is responsible for regulating water, salt, and potassium levels in the blood.
- Diabetic ketoacidosis - Caused when blood glucose can't get to the cells for energy due to lack of insulin. The body breaks down fat as an alternate energy sauce, which causes the blood to become too acidic and hyperglycemia (high blood sugar). Acidosis and hyperglycemia can cause potassium to move from the cells and into the blood circulation.
- Reperfusion injury occurs when blood flow is restored after a blockage has occurred (such as blood clot). During blockage (known as ischemia), cells are deprived of oxygen leading to a cascade of biochemical reactions occur leading to toxic build up. Once blood flow is restored, these by products are released into the circulatory system and hyperkalemia can occur.
Not all cats will show signs of hyperkalemia. When they do occur, it is usually when levels have become dangerously high (above 7 mmol/L). Symptoms of hyperkalemia may include:
- Cardiac arrhythmias
- Muscle weakness
- Gastrointestinal disturbances
In addition to the symptoms listed above, the underlying cause will also produce symptoms.
- Increased urination and drinking
- Anorexia (loss of appetite)
- Bad breath
- Loss of coordination
- Frequent trips to the litter tray, your cat may be seen straining, crying, licking his genitals
- A small amount of urine may be produced or none at all if he has become completely blocked
- Blood in the urine
- Abdominal pain
- Abdominal swelling
- Inability to urinate at all
- Abdominal pain
- Abdominal swelling
- Increased thirst and urination
- Fruity smelling breath
- Vomiting and diarrhea
- Weight loss
- Biochemical profile. Elevated BUN and creatinine levels which will be elevated in cats with kidney disease as well as a cat who has a urinary blockage. Hyperglycemia may occur in cats with diabetes or ketoacidosis.
- Complete blood count to evaluate the blood. If red blood cell count is reduced that may point towards chronic kidney failure.
- Urinalysis to look for blood in the urine, urinary crystals, white blood cells and evaluate kidney function.
- ECG may also be advised to evaluate the heart for arrhythmias.
- Ultrasound or abdominal x-rays may be performed to check the bladder and urinary tract for rupture or blockage.
Additional tests may be required depending on the results of bloodwork to assist with diagnosis.
Treatment is aimed at addressing the underlying cause and may include:
- Kidney failure (chronic) - Low protein and phosphate diet along with phosphorous binders, which reduce the absorption of phosphate.
- Kidney failure (acute) - Find and treat the underlying cause, this may include inducing vomiting or activated charcoal to reduce absorption of ingested toxins, supportive care will also be required in cats suffering from acute kidney failure.
- Ketoacidosis - Proper management of diabetes.
- Urinary blockage - Removing the blockage, usually by catheterisation. If the blockage can't be relieved via the methods listed above, an emergency perineal urethrostomy will be performed. This involves surgery to create a new urethral opening.
- Removal of urine from the bladder or abdomen may also be performed if the cat is blocked or has a ruptured bladder.
- Ruptured bladder - Surgery is required to repair the damaged bladder.
- Addison's disease - Lifelong administration of the deficient adrenal hormones.
In addition to treating the underlying condition, fluid therapy may be administered to increase urine output, which reduces levels of potassium in the blood. This may include:
- 0.9% sodium chloride (NaCl) to increase urination
- 10% calcium gluconate to help counteract the effects of hyperkalemia on the heart
- Sodium bicarbonate (NaHCO3) to correct acidosis
- Glucose (with or without insulin) to push potassium back into the intracellular fluid
Follow up appointments with your veterinarian will be necessary to monitor your cat's heart.
Cats who have had a urinary blockage are at risk of a recurrence. Your veterinarian may recommend a change in diet if your cat is at risk. This may include a switch to wet food (raw or canned) or a prescription diet.