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HWN Suggests

Hypernatremia

It is important not to correct the serum sodium concentration too rapidly due to the risk of cerebral oedema (in chronic hypernatraemia, the aim is to lower the serum sodium level by 10 mmol/L/day). When replacing any fluid deficits, enteral free water replacement is preferred where possible (including administration via nasogastric tube if needed).

If enteral intake is not possible, intravenous fluid choice includes 5% dextrose (most preferred), 0.9% saline (used if evidence of volume depletion) or Hartmann’s solution. Adjust rates and fluid compositions depending on sodium levels and fluid status accordingly.

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  Free Water Deficit in Hypernatremia

Calculates free water deficit by estimated total body water.

 EM@3AM: Hypernatremia

Most cases of hypernatremia are due to a total body water deficit. Heatstroke, increased insensible losses from burns or sweating, and gastrointestinal fluid losses from diarrhea or protracted vomiting can all result in hypernatremia. Patients without access to water or impaired thirst mechanisms are at particular risk for hypernatremia, including elderly bedridden patients, those with mental impairment, and patients who are in a coma.

 Improving on the Adrogué–Madias Formula

The Adrogué–Madias (A-M) formula is correct as written, but technically, it only works when adding 1 L of an intravenous (IV) fluid. For all other volumes, the A-M algorithm gives an approximate answer, one that diverges further from the truth as the IV volume is increased.

Articles of Interest

Hypernatremia

Think water depletion...

Hyponatremia and Hypernatremia: A Practical Guide to Disorders of Water Balance

Hyponatremia and hypernatremia are disorders of water balance. Hyponatremia is usually due to failure to excrete excess water rather than excess sodium loss. Hypernatremia is usually due to inadequate water intake or water loss rather than excess sodium intake.

Treatment of acute hypernatremia caused by sodium overload in adults

Treatment of hypernatremia typically involves infusion of hypotonic solutions such as 5% dextrose in water (D5W), or in rare occasions, hemodialysis, to lower serum sodium concentration [Na].

Resources

International Emergency Medicine Education Project

Hypernatremia should be excluded in any patient who presents with altered mental status, particularly, the very young or old and those with abnormal basal cognition.