Hyponatremia in primary care

Hyponatremia is the most frequently observed electrolyte abnormality; its mild form is associated with cognitive deficit and falls, but in hospitalized patients it is associated with increased mortality.

In primary care, hyponatremia is usually found in patients who are monitored for chronic diseases. This motivates a reassessment aimed at finding underlying causes, such as medications, cancer or adrenal insufficiency.

Hyponatremia is defined by a serum sodium value below the reference range, which is usually 135-145 mEq /l. It is often subdivided into mild, moderate, severe and life threatening, based on the combination of symptomatology and sodium level.

However, there is little correlation between symptomatology and serum sodium level, so both must be taken into account when considering the urgency of shunt and subsequent management. It can be acute (arbitrarily defined as an onset within 48 hours), chronic (> 48 hours) or unknown (its management should be similar to that of the chronic).

What considerations should you consider?

• Mild hyponatremia is associated with an increased risk of falls and osteoporosis.

• The assessment of volume status helps guide differential diagnosis and therapeutic options.

• Medications such as diuretics, antidepressants, antipsychotics and antiepileptic drugs are common causes of hyponatremia.

• Older people are particularly at risk of developing hyponatremia and suffering its consequences.

• Verify thyroid function and cortisol at 9 am in all patients with hypovolemic and euvolemic hyponatremia.

Evaluation in primary care

Patients with asymptomatic mild hyponatremia (130-135 mEq / l) can, at least initially, be managed in primary care. In practice, this involves keeping a story focused on identifying the symptoms of an underlying cause, reviewing the medications you take and examining the condition of the fluids. Initial investigations include urinary osmolality, urinary sodium and other blood tests such as cortisol at 8 am.

Depending on the clinical picture, initially a change in medication and / or fluid restriction may be appropriate. Mild and well tolerated hyponatremia may be clinically acceptable if the patient remains stable with the medication.

The patient should be checked at intervals determined according to the clinical context, to establish if the hyponatremia has resolved and if it is indicated to refer it to a specialist. For example, if the patient is clinically well but taking a medication that causes hyponatremia, the medication should be discontinued, provided that its suspension is safe, and then, after 2 weeks, recheck the sodium level.

If initial studies suggest an inappropriate antidiuresis syndrome, the underlying cause should be considered, regardless of whether the sodium level improves.

Severe symptoms are caused by cerebral edema and should be managed as in severe hyponatremia, regardless of current serum sodium.

A patient with severe, apparently asymptomatic, biochemical hyponatremia also requires careful management, since correction too quickly can lead to complications.

It is recommended to refer any person with a sodium level

Medication and hyponatremia

A common cause of hyponatremia is pharmacotherapy. The most frequent people responsible are thiazide diuretics.

• In an observational study in primary care, 13.7% of patients who received thiazides had documented hyponatremia.

• Another study found that 29% of patients hospitalized with hyponatremia (

• Indapamide, a thiazide-like drug and hydrochlorothiazide are also involved in hyponatremia.

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