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Basics ⬇

Outline

BASICS

Overview!!navigator!!

  • Hyperkalemia is defined as an elevated concentration of potassium in serum/plasma
  • Potassium is the major intracellular cation in biologic systems
  • Plays a major role in determining the resting membrane potential of excitable tissue
  • Readily absorbed by the gastrointestinal tract in health
  • Excretion of excess potassium is performed by the kidney
  • The quantity of potassium in extracellular fluid is <2% of total body potassium; as such, serum potassium evaluation is a poor assessment of whole-body potassium status
  • Changes in serum potassium concentration can have marked effects on muscle and nervous tissue
  • The 2 largest clinically significant body potassium stores are erythrocytes and skeletal muscle

Signalment!!navigator!!

  • Any breed, age, or sex.
  • Uroperitoneum in neonates
  • HYPP in Quarter Horses

Signs!!navigator!!

  • Skeletal muscle weakness
    • Fasciculations
    • Stiffness, myotonia
    • Staggering gait
    • Collapse
  • Bradycardia, other cardiac dysrhythmias
  • Sweating, anxiety
  • Sudden death

Causes and Risk Factors!!navigator!!

  • Strenuous exercise—causes transient hyperkalemia
    • Likely reflects lactic acidemia that develops during exercise, but myocytes also release potassium
    • Potassium may be responsible for peripheral vasodilation during exercise, increasing blood flow to skeletal muscle
  • Rhabdomyolysis (or any condition resulting in severe, diffuse cellular injury/necrosis, resulting in leakage of intracellular potassium)
  • Intravascular hemolysis (severe)
  • HYPP—major cause of intermittent hyperkalemia
  • Poor sample handling—leakage of intracellular potassium from erythrocytes and/or platelets; samples should be spun and removed from clot as soon as possible after collection
  • Acidemia—intracellular translocation of interstitial fluid hydrogen ion in exchange for intracellular potassium
    • Mild to moderate elevation in serum potassium
    • Affected horses likely to have total-body potassium depletion due to primary disease
  • Acute kidney injury or chronic renal failure
    • Inconsistent finding
    • Anuria/oliguria more likely to cause clinically significant hyperkalemia
  • Iatrogenic—IV parenteral potassium supplementation
  • Uroperitoneum—postrenal obstruction, decreased potassium clearance
  • Hyperosmolality

Diagnosis ⬆ ⬇

Outline

DIAGNOSIS

CBC/Biochemistry/Urinalysis!!navigator!!

Biochemistry—increased potassium concentration (>5.0 mmol/L).

Other Laboratory Tests!!navigator!!

Arterial blood gas analysis may reveal acidemia.

Imaging!!navigator!!

Dependent on the underlying cause (e.g. ultrasonography to detect free abdominal fluid in foals with uroperitoneum).

Other Diagnostic Procedures!!navigator!!

  • ECG
    • Peaked, tented T waves
    • Decreased Q–T interval
    • Decreased amplitude of P waves
    • Widened QRS complexes
    • Sinus bradycardia
    • Changes may be seen when plasma potassium level >6 mEq/L
    • Changes may be marked with plasma potassium level >8 mEq/L
    • Plasma potassium level >9–10 mEq/L often fatal
      • Ventricular fibrillation
      • Asystole

Treatment ⬆ ⬇

TREATMENT

  • Dependent on the underlying cause
  • Hyperkalemia should be addressed as an emergency
  • Diuresis with potassium-free polyionic fluids may be helpful (e.g. 0.9% NaCl)
    • In mild cases, may be all that is required
    • More severe cases require additional emergency medical treatment (see Drug(s) of Choice)
    • Use caution in patients with renal disease
  • Hyperkalemia should be corrected prior to induction of anesthesia to minimize cardiovascular and musculoskeletal complications
    • Hyperkalemic patients should be offered potassium-poor diets

Medications ⬆ ⬇

Outline

MEDICATIONS

Drug(s) of Choice!!navigator!!

  • Calcium gluconate
    • 0.2–0.4 mL/kg of 23% solution diluted in 1–2 L 5% dextrose, administered slowly IV
    • Calcium is cardioprotective
  • Dextrose/insulin
    • Insulin causes rapid intracellular translocation of potassium
    • Dextrose induces endogenous insulin release
    • Oral glucose may be given in emergency (oats, light corn syrup) but is not appropriate alone for severe cases
    • IV dextrose preferred (5%, 4.4–6.6 mL/kg)
  • Sodium bicarbonate
    • Use care—rapid alkalinization of patients with metabolic acidemia may result in acute, profound hypokalemia
    • 1–2 mEq/kg IV as isotonic solution
  • Diuretics
    • Acetazolamide (2–4 mg/kg PO every 12 h) is a potassium-wasting, carbonic anhydrase inhibitor diuretic that may be effective for managing horses with HYPP

Contraindications/Possible Interactions!!navigator!!

Do not administer sodium bicarbonate with calcium-containing fluids.

Follow-up ⬆ ⬇

Outline

FOLLOW-UP

Patient Monitoring!!navigator!!

  • ECG monitoring
  • Serial evaluation of serum potassium concentration

Possible Complications!!navigator!!

  • Cardiac dysrhythmias
  • Sudden death

Miscellaneous ⬆ ⬇

Outline

MISCELLANEOUS

Abbreviations!!navigator!!

HYPP = hyperkalemic periodic paralysis

Suggested Reading ⬆ ⬇

Borer KE, Corley KTT. Electrolyte disorders in horses with colic. Part 1: potassium and magnesium. Equine Vet Educ 2006;18(5):266–271.

Author(s) ⬆

Author: Teresa A. Burns

Consulting Editor: Sandra D. Taylor