section name header

Basics ⬇

Outline

BASICS

Overview!!navigator!!

  • Hypokalemia is defined as decreased potassium concentration in serum/plasma, usually <2.5 mEq/L (depends on reference values of laboratory performing the assay)
  • 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 GI tract in health (typically in excess of body need); the average equine diet is potassium-rich, easily providing the daily requirement of 23 g for an adult horse
    • Alfalfa hay—13 lb (6 kg) provides 145 g potassium
    • Grass hay (average)—16 lb (7 kg) provides 121 g potassium
    • Trace mineral salt—2 oz provides 145 g potassium
  • Excretion of excess potassium from dietary intake is performed by the kidney, preventing potentially toxic hyperkalemia in health
  • Renal conservation of potassium is nonspecific and inefficient, developing over the course of several days in horses with decreased dietary potassium intake and/or excessive potassium losses. This aspect of potassium physiology increases risk of clinically significant hypokalemia in horses with inappetence or potassium-wasting diseases
  • The quantity of potassium in the ECF is <2% of the total body potassium; as such, plasma potassium evaluation is a poor assessment of whole-body potassium status
  • The ratio of ICF to ECF potassium concentration is critical to determining the resting membrane potential; changes in plasma potassium concentration can have marked effects on excitable tissue (muscle and nervous tissue)
  • May be due to total body potassium deficit, or, more likely, may reflect a shift in potassium distribution between ECF and ICF
  • Hypokalemia is uncommon in horses with normal feed intake

Signalment!!navigator!!

Any breed, age, or sex.

Signs!!navigator!!

  • Usually noted when serum potassium concentration falls below 1.8 mEq/L
  • Weakness
  • Collapse
  • Arrhythmia (ventricular premature beats, ventricular tachycardia)
  • Sudden death
  • Ileus

Causes and Risk Factors!!navigator!!

  • Alkalemia (any cause)—extracellular potassium is exchanged for intracellular hydrogen ion in an attempt to restore acid–base equilibrium
  • Profuse sweating (sweat contains high concentration of potassium)
  • Renal tubular acidosis (types 1 and 2)
  • Decreased dietary intake (inappetence for any reason)
  • GI loss
    • Diarrhea
    • Nasogastric reflux
  • Iatrogenic
    • Sodium bicarbonate
    • Dextrose-containing fluids
    • Insulin
    • Prolonged parenteral nutrition

Diagnosis ⬆ ⬇

Outline

DIAGNOSIS

Differential Diagnosis!!navigator!!

  • Muscular weakness—underlying myopathy, other electrolyte, acid–base abnormalities (e.g. hypocalcemia, hypomagnesemia)
  • Cardiac arrhythmia—underlying cardiomyopathy, other electrolyte, acid–base abnormalities

CBC/Biochemistry/Urinalysis!!navigator!!

  • CBC—may be helpful for identification of underlying disease
  • Biochemistry—evidence of underlying disease may be present; other electrolyte abnormalities, such as hypomagnesemia and hypocalcemia, may be noted and may exacerbate clinical signs of hypokalemia
  • Urinalysis—fractional clearance of potassium is variably affected

Other Laboratory Tests!!navigator!!

Arterial blood gas analysis may reveal alkalemia.

Diagnostic Procedures!!navigator!!

ECG

  • Peaked P waves
  • Decreased amplitude of T waves
  • Increased QRS duration
  • Ventricular ectopic rhythms (ventricular premature contractions, ventricular tachycardia)

Treatment ⬆ ⬇

TREATMENT

  • Definitive treatment of underlying cause is required
  • Potassium-rich diet should be offered (e.g. legume hay)
  • Oral supplementation with potassium chloride is typically sufficient in mild cases
    • 25–40 g/day via nasogastric tube in divided doses
  • Potassium chloride supplementation IV (20–40 mEq/L; no more than 0.5 mEq/kg/h to avoid potentially dangerous hyperkalemia)

Medications ⬆ ⬇

Outline

MEDICATIONS

Drug(s) of Choice!!navigator!!

Potassium chloride (see Treatment).

Contraindications/Possible Interactions!!navigator!!

  • Supplemental potassium should be given with caution in patients with known renal insufficiency; careful monitoring of serum potassium concentration should be performed
  • Medications that may exacerbate hypokalemia should be avoided:
    • Sodium bicarbonate
    • Glucose/dextrose, insulin
    • Diuretics (acetazolamide, furosemide)

Follow-up ⬆ ⬇

Outline

FOLLOW-UP

Patient Monitoring!!navigator!!

  • Serial assessment of serum potassium concentration
  • ECG monitoring should be continued until normal

Possible Complications!!navigator!!

  • Cardiac arrhythmias (especially idioventricular rhythms)
  • Sudden death
  • Ileus, colic
  • Predisposition to exertional rhabdomyolysis/myopathy

Miscellaneous ⬆ ⬇

Outline

MISCELLANEOUS

Abbreviations!!navigator!!

  • ECF = extracellular fluid
  • GI = gastrointestinal
  • ICF = intracellular fluid

Suggested Reading ⬆ ⬇

Johnson PJ. Electrolyte and acid-base disturbances in the horse. Vet Clin North Am Equine Pract 1995;11:491–514.

Stäempfli H, Oliver-Espinosa O. Serum potassium. In: Smith BP, ed. Large Animal Internal Medicine, 5e. St. Louis, MO: Elsevier Mosby, 2015:357–358.

Author(s) ⬆ ⬇

Author: Teresa A. Burns

Consulting Editor: Sandra D. Taylor

Additional Further Reading ⬆

Click here for Additional Further Reading