Canis ISSN: 2398-2942

Fluid therapy: for electrolyte abnormality

Contributor(s): Elisa Mazzaferro, Sheilah Robertson, Claire Waters

Sodium

Hyponatremia

  • Serum [Na+] <136 mmol/l Blood biochemistry: sodium Hyponatremia.
  • Plasma osmolality may be normal, high or low (n = 290-310 mOsm/kg)
  • Retention of water, eg in response to decreased blood volume or blood pressure.
  • Causes include:
    • Gastrointestinal loss.
    • Congestive cardiac failure.
    • Diuretic therapy.
    • Hypoadrenocorticism.
  • Clinical signs:
    • Lethargy.
    • Weakness.
    • Vomiting.
    • Muscle cramping.
    • Seizures Seizures - due to changes in brain volume.
    • Wide QRS and ST segment elevation.
    • Water retention will increase bodyweight.
  • Severe hyponatremia (<110 mmol/l) give 3% saline over 24 h: mmol Na+ required = 0.2 x bodyweight (kg) x (normal [Na+] - patient's [Na+]).
    Correct slowly as oversupplement, too fast can cause central pontine myelinolysis.
  • Less severe (<120 mmol/l)  correct underlying cause and give 0.9% saline.
    For composition of solutions see the Parenteral fluids comparison table Parenteral fluids comparison table.

Hypernatremia

  • Serum [Na+] = >156 mmol/l Hypernatremia.
  • Free water loss, eg heat exhaustion Fluid therapy: for heat exhaustion.
  • Diabetes insipidus.
  • Can be caused by excess administration, eg giving sodium bicarbonate.
  • Shift of water from ICS → ECS → cell dehydration.
  • Clinical signs - related to the CNS:
    • Lethargy.
    • Confusion.
    • Muscle weakness.
    • Seizures Seizures.
    • Coma.
  • Give hypotonic fluid, eg 5% dextrose in water or 0.45% NaCl.
    For composition of solutions see the Parenteral fluids comparison table.
  • In patients with long-standing hypernatremia, correct slowly to prevent cerebral edema.
  • Equation for replacement of H2O:
    • Free water deficit = 0.4x lean bodyweight (kg) x ((plasma[Na+]/140) -1).
      Do not lower plasma [Na+] more than 15 mEq/L in first 8 h.

Potassium

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Calcium

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Further Reading

Publications

Refereed papers
  • Brady C A et al(1999)Severe neurologic sequelae in a dog after treatment of hypoadrenal crisis. JAVMA215(2), 222-225.
  • Churcher R K et al(1999)Suspected myelinolysis following rapid correction of hyponatremia in a dog. J Am Anim Hosp Assoc35(6), 493-497.

 

Other sources of information

  • Wingfield W E (1997)Veterinary Emergency Medicine Secrets.Eds Hanley & Belfus ISBN 1560534214.


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