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Sodium Imbalances

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References:

  1. Saunders Comprehensive Review for the NCLEX-RN Examination, 9th Edition, ISBN 978-032-37-9530-2, by Linda Anne Silvestri, Angela E. Silvestri, and Jessica Grimm (Ch. 8, pp. 88-105)

Hyponatremia

Normal Serum Sodium Level: 135 to 145 mEq/L (135 to 145 mmol/L)

Imbalances related to sodium is closely tied with fluid volume imbalances. This may be caused by:

  1. Increased sodium excretion: diaphoresis, diuretics, vomiting, diarrhea, wound drainage (especially gastrointestinal), kidney disease, and decreased secretion of aldosterone (the salt-saving hormone).
  2. Inadequate sodium intake: fasting/NPO status, low-salt diet
  3. Dilution of serum sodium: excessive ingestion of or irrigation with hypotonic fluids; kidney disease; freshwater drowning; SIADH; hyperglycemia; heart failure

Assessment

  1. Cardiovascular: symptoms depend on vascular volume.
    • Normovolemic: rapid pulse rate, normal blood pressure
    • Hypovolemic: thready, weak, rapid pulse rate; hypotension; flat neck veins; normal or low central venous pressure
    • Hypervolemic: rapid, bounding pulse; blood pressure is normal or elevated; normal or elevated central venous pressure
  2. Respiratory: shallow, ineffective respiratory movement is a late manifestation related to skeletal muscle weakness.
  3. Neuromuscular: generalized skeletal muscle weakness that is worse in the extremities; diminished deep tendon reflexes
  4. Central Nervous System:
    • Headache
    • Personality changes
    • Confusion
    • Seizures
    • Coma
  5. Gastrointestinal:
    • Nausea
    • Increased motility and hyperactive bowel sounds
    • Abdominal cramping and diarrhea
  6. Renal: increased urinary output
  7. Integumentary: dry mucous membranes
  8. Laboratory Findings: <135 mEq/L serum sodium concentration; decreased urinary specific gravity

Interventions

Interventions depend on the cause and accompanying conditions:

  • If a fluid volume deficit (hypovolemia) is present, IV sodium chloride infusions are administered to restore sodium content and fluid volume.
  • If a fluid volume excess (hypervolemia) is present, osmotic diuretics may be prescribed to promote the excretion of water, but not sodium.
  • Treatment depends on whether the hyponatremia is chronic or acute; if the imbalance is severe, hospitalization may be required to closely monitor sodium levels, avoid rapid sodium shifts, and monitor the patient’s neurological status.
  • A sudden correction of hyponatremia may cause osmotic demyelination (sudden shift of fluid from the brain to circulation results in dehydration and destruction of myelin in the white matter).
  • If hyponatremia is caused by SIADH, medications that antagonize ADH may be administered.
  • Instruct the client to increase oral sodium intake as prescribed, and inform the client about the foods to include in the diet: sodium chloride (table salt), milk, beets, celery, some drinking waters, food products (Worcestershire sauce, soy sauce, onion salt, garlic sault, bouillon cubes), processed meats, canned soups and vegetables, processed baked foods, and fast foods.
  • If the client is taking lithium, monitor the lithium level, because hyponatremia can reduce lithium excretion and therefore potential toxicity.

Hyponatremia precipitates lithium toxicity in a client taking this medication.

Hypernatremia

A serum sodium level that exceeds 145 mEq/L (145 mmol/L). This is caused by:

  1. Decreased sodium excretion: corticosteroids, Cushing’s syndrome, kidney disease, hyperaldosteronism
  2. Increased sodium intake: excessive oral sodium ingestion or administration of sodium-containing IV fluids.
  3. Decreased water intake leading to sodium concentration, from fasting or NPO status.
  4. Increased water loss leading to sodium concentration: increased rate of metabolism, fever, hyperventilation, infection, excessive diaphoresis, watery diarrhea, and diabetes insipidus.

Assessment

  1. Cardiovascular: heart rate and blood pressure responsive to vascular volume status
  2. Respiratory: pulmonary edema if hypervolemia is present
  3. Neuromuscular: an early manifestation of spontaneous muscle twitches, and later skeletal muscle weakness and diminished deep tendon reflexes (same as hyponatremia)
  4. Central Nervous System: altered cerebral function (most common)
    • If normovolemic or hypovolemic, agitation, confusion, and seizures
    • If hypervolemic, lethargy, stupor, and coma
  5. Gastrointestinal: extreme thirst
  6. Renal: decreased urine output
  7. Integumentary: dry and sticky tongue and mucous membranes; dry and flushed skin; presence or absence of edema depending on fluid volume changes.
  8. Laboratory Findings: serum sodium level more than 145 mEq/L (145 mmol/L); increased urine specific gravity

Interventions

  • If fluid loss is the cause, prepare to administer IV infusions to restore fluid volume.
  • If inadequate renal excretion of sodium is the cause, prepare to administer diuretics that promote sodium excretion.
  • Restrict sodium and fluid intake as prescribed.
  • In some situations, IV fluid of D5W will be prescribed to lower the sodium level. If the client has diabetes, monitor glucose closely for hyperglycemia.

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