Treatment Of Chronic Symptomatic Hyponatremia

*The sum of urinary cations (U^ + Uk) should be less than the concentration of infused sodium, to ensure excretion of electrolyte-free water.

Acute hyponatremia (duration < 48 hrs)

Increase serum sodium rapidly by approximately 2 mmol/L/h until symptoms resolve Full correction probably safe but not necessary

Chronic hyponatremia (duration > 48 hrs)

Initial increase in serum sodium by 10% or 10 mmol/L

Perform frequent neurologic evaluations; correction rate may be reduced with improvement in symptoms At no time should correction exceed rate of 1.5 mmol/L/h, or increments of 15 mmol/d

Measure serum and urine electrolytes every 1-2 h

Calculate the net water loss needed to raise the serum sodium (S^) from 110 mEq/L to 120 mEq/L in a 50 kg person.

Example

Current SNa X Total body water (TBW) = Desired SNa X New TBW

Assume that TBW = 60% of body weight

120 mEq/L

Thus the electrolyte-free water loss needed to raise the SNa to 120 mEq/L = Present TBW - New TBW = 2.5 L

Calculate the time course in which to achieve the desired correction (1 mEq/h)—in this case, 250 mL/h

Administer furosemide, monitor urine output, and replace sodium, potassium, and excess free water lost in the urine

Continue to monitor urine output and replace sodium, potassium, and excess free water lost in the urine

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