F+E Highlights: Hyponatremia

Hyponatremia refers to

a serum sodium level that is less than 135 mEq/L (135 mmol/L)

In what forms can hyponatremia present?

Acute or chronic.

What commonly causes acute hyponatremia in surgical patients, and why is it called dilutional hyponatremia?

Fluid overload; excess water dilutes the sodium in the bloodstream.

How does chronic hyponatremia differ from acute hyponatremia?

It occurs more frequently outside hospitals, lasts longer, and has less serious neurologic effects.

What is exercise-associated hyponatremia?

Hyponatremia occurring during or after prolonged exercise

which individuals are more at risk for exercise-associated hyponatremia? Why?

women and smaller-stature individuals, due to excessive fluid intake or sodium loss through perspiration, especially in extreme temperatures.

What is the primary cause of hyponatremia?

An imbalance of water rather than sodium.

What factors influence the clinical manifestations of hyponatremia?

The cause, magnitude, and speed of the sodium deficit.

Clinical Manifestations of Hyponatremia

Poor skin turgor, dry mucosa, headache, decreased saliva production, orthostatic fall in blood pressure, nausea, vomiting, and abdominal cramping.

What neurologic changes can occur with hyponatremia, and what causes them?

Altered mental status, status epilepticus, and coma caused by cellular swelling and cerebral edema.

What happens to water movement in cells as extracellular sodium levels decrease?

Water is pulled into the cells because the intracellular fluid becomes relatively more concentrated.

How does the speed of serum sodium decrease affect cerebral edema and mortality in hyponatremia?

Acute decreases cause more cerebral edema and higher mortality than slowly developing hyponatremia.

What signs may occur when serum sodium falls below 115 mEq/L?

Lethargy, confusion, muscle twitching, focal weakness, hemiparesis, papilledema, seizures, and death due to increasing intracranial pressure.

What does a targeted assessment for hyponatremia include?

History and physical exam with focused neurologic assessment, evaluation of signs and symptoms, lab results, review of current IV fluids, and all medications the patient is taking.

What is the most common treatment for hyponatremia?

Careful administration of sodium orally, via nasogastric tube, or parenterally.

Why is sodium easily replaced in patients who can eat and drink?

Because sodium is consumed abundantly in a normal diet.

What intravenous solutions may be prescribed for patients who cannot consume sodium orally?

Lactated Ringer’s solution or isotonic saline (0.9% sodium chloride).

What is the maximum recommended increase in serum sodium in 24 hours, and why?

No more than 12 mEq/L in 24 hours to avoid neurologic damage from demyelination.

Under what conditions can overcorrection of serum sodium lead to serious complications?

When serum sodium exceeds 140 mEq/L too rapidly or in the presence of hypoxia or anoxia.

How should highly hypertonic sodium solutions be administered in hyponatremia, and why is close monitoring required?

They should be administered slowly, with close monitoring, because only small volumes are needed to raise serum sodium.

What should a nurse assess for when administering fluids to patients with cardiovascular disease?

Hemodynamic signs of circulatory overload, including cough, dyspnea, jugular venous distention, dependent edema, 1–2 lb weight gain in 24 hours, and auscultation for lung crackles indicating pulmonary edema.