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Both hyponatremia and hypernatremia are common problems within the newborn intensive care unit. Hyponatremia, defined by a serum sodium less than 130 mEq/L, frequently occurs as a result of an inability to secrete a water load, increasing sodium losses, or poor sodium intake. Hypernatremia, defined as serum sodium greater than 150 mEq/L, frequently occurs as a result of increased losses of free body water, insufficient water intake, or inadvertent excess sodium administration.


To provide guidance for neonatologists, pediatricians, advanced practitioners, and nurses on management of disorders of sodium equilibrium in the neonatal period.


Treatment of hyponatremia (serum sodium <130 mEq/L) and hypernatremia (serum sodium >150 mEq/L) in newborn infants continues to be problematic. There is a significant lack of evidence to support specific management guidelines, and physiologic changes of the developing premature infant further confound treatment. These guidelines were developed with the intention to assemble and distribute more specific treatment methodologies to guide the clinician.



Hyponatremia (Serum Sodium <130 mEq/L)


Defined by decreased total body sodium and total body water.

  • If the urine sodium <20 mEq/L, one should consider extra-renal losses (i.e., vomiting, diarrhea, drainage tubes or fistulas, pleural effusions, ascites, ileus, and necrotizing enterocolitis).

  • Sodium content (mmol/L) of various body fluids:

    • Stomach: 20–80

    • Small intestine: 100–140

    • Bile: 120–140

    • Ileostomy: 45–135

    • Diarrheal stool: 10–90

  • If the urine sodium >20 mEq/L, one should consider renal losses (i.e., diuretics, osmotic diuresis, contraction alkalosis, mineralocorticoid deficiency, mineralocorticoid resistance, Fanconi syndrome, Bartter syndrome, or obstructive uropathy).

Treatment. Volume expansion.


  1. Treat underlying cause.

  2. In cases of symptomatic hyponatremia or Na <120 mEq/L, correction to a serum sodium above 120 mEq/L with 3% saline solution (0.513 mEq of sodium per milliliter) is recommended over 4–6 hours in addition to ongoing maintenance fluids at the appropriate rates suggested below. Calculation of the sodium deficit (mEq) and the use of fluids with the applicable sodium concentration may aid the clinician in more appropriate replacement of sodium deficits (Table 17.1).

    Total sodium deficit (mEq) = (ideal Na – actual Na) × 0.6 × weight in kg

    1. Term infants: 60–80 mL/kg/day.

    2. Preterm infants 1250 g to 2000 g: 80–100 mL/kg/day, advancing by 20 mL/kg/day up to 140 mL/kg/day.

    3. Preterm infants <1250 g: 120 mL/kg/day, advancing by 20 mL/kg/day up to 140 mL/kg/day or higher depending on persistent insensible losses.

  3. Asymptomatic hyponatremia above 120 mEq/L can be corrected more slowly over 24−48 hours with 0.45% (0.077 mEq of sodium per milliliter) and 0.9% (0.154 mEq of sodium per milliliter) saline solutions.

  4. Follow serum sodium concentrations closely at a minimum of every 6–12 ...

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