Potassium is an essential electrolyte for proper muscle function. However, high blood potassium levels cause a life-threatening condition known as hyperkalemia.
Langdon Fielding, DVM, Dipl. ACVECC, ACVSMR, of the Loomis Basin Equine Medical Center, in Penryn, California, summarized treatment options at the 2016 American Association of Equine Practitioners Convention, held Dec. 3-7 in Orlando, Florida.
Causes of Hyperkalemia
The two main causes of hyperkalemia include failure of the kidneys to remove potassium (which gets excreted in the urine) and abnormal potassium release from cells. Horses with a history of hyperkalemic periodic paralysis (HYPP, a genetic muscle disorder of Quarter Horses), compromised kidney function, or massive cellular damage (due to injury or disease) are at greater risk of developing hyperkalemia, said Fielding.
Signs of Hyperkalemia
Muscle weakness is a classic sign of hyperkalemia and, while on its own it’s a fairly general symptom, when accompanied by changes in cardiac rhythm, veterinarians should suspect hyperkalemia. Cardiac changes are not always present in hyperkalemia cases, Fielding noted to veterinarians, so don’t rule out a diagnosis in the absence of such abnormalities.
One treatment option is administering intravenous (IV) calcium borogluconate (23%) in a 5-liter bag of isotonic fluids. This calcium-containing fluid will not reduce plasma potassium concentrations, but it can help protect the heart muscle from their negative effects.
Administering IV dextrose causes the body to produce more insulin, which shifts potassium from the blood into many types of cells (muscle, adipose, etc.). Veterinarians can administer insulin IV in conjunction with dextrose, but Fielding noted that, due to other risk factors, they should only use this technique when they can monitor blood glucose can be closely.
Beta agonists are a class of drugs that relax airway muscles. Like insulin, beta agonists drive potassium into cells. However, more research is needed in horses, as most beta agonist data has been conducted in other species. Veterinarians might administer diuretics to help increase potassium excretion in urine, but Fielding said not give them to dehydrated horses
Historically, researchers have recommended administering sodium bicarbonate to treat hyperkalemia, but clinical trials have shown it to have little to no benefit, and so it should not be a primary treatment, said Fielding.
Recognizing hyperkalemia can be difficult. Consider the horse’s health history, and if you suspect hyperkalemia, initiate treatment as soon as possible and monitor the horse for signs of improvement.