Medical Care
Medical care involves the correction of hypernatremia and treating the underlying disease.
However, avoid rapid correction of sodium levels in patients with chronic hypernatremia, because a rapid decline in the serum sodium concentration can cause cerebral edema. [10]
The recommended rate of sodium correction is 0.5 mEq/h or as much as 10-12 mEq/L in 24 hours. Dehydration should be corrected over 48-72 hours. Guidelines for hydration management have been established. [11] If the serum sodium concentration is more than 200 mEq/L, peritoneal dialysis should be performed using a high-glucose, low-sodium dialysate.
Body water deficit
Body water deficit may be calculated. The equations used are based on a goal of plasma sodium concentration of 145 mEq/L. In children, total body water (TBW) is 60% of their lean body weight. Therefore, TBW = 0.6 X weight. Babies are an exception to these equations and may have a TBW as much as 80% of their body weight.
One of the following equations may be used to calculate body water deficit:
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Water deficit (in L) = [(current Na level in mEq/L ÷ 145 mEq/L) - 1] X 0.6 × weight (in kg)
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Water deficit (in L) = [(current Na level in mEq/L - 145 mEq/L)/145 mEq/L)] × 0.6 X weight (in kg)
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Water deficit (in L) = [1- (145 mEq/L ÷ current Na level in mEq/L)] × 0.6 × weight (in kg)
An example calculation is: A child weighs 10 kg and has a plasma sodium concentration of 160 mEq/L. By using the first equation, water deficit (in L) = [(160 mEq/L ÷ 145 mEq/L) - 1] X 0.6 × 10 = 0.62 L.
Replacement fluid
The volume of replacement fluid needed to correct the water deficit is determined by using the concentration of sodium in the replacement fluid. The replacement volume can be determined as follows:
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Replacement volume (in L) = TBW deficit × 1 ÷ [1 - (Na concentration in replacement fluid in mEq/L ÷ 154 mEq/L)]
An example calculation is: If the patient from the example calculation above has a TBW of 0.62, and if the replacement fluid contains 0.2% NaCl (Na concentration of 34 mEq/L), the replacement volume (in L) = 0.62 L × 1 ÷ [1 - (34 mEq/L ÷ 154 mEq/L)] = 0.79 L. This volume has to be replaced slowly over 48-72 hours.
Intravenous fluid
The election of intravenous fluid is based on the following:
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If the patient is hypotensive, normal saline (lactated Ringer solution, or 5% albumin solution) should be used regardless of a high serum sodium concentration.
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In hypernatremic dehydration, 0.45% or 0.2% NaCl should be used as a replacement fluid to prevent excessive delivery of free water and a too-rapid decrease in the serum sodium concentration.
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In cases of hypernatremia caused by sodium overload, sodium-free intravenous fluid (eg, 5% dextrose in water) may be used, and a loop diuretic may be added.
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The serum sodium concentration should be monitored frequently to avoid too-rapid correction of hypernatremia.
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In cases of associated hyperglycemia, 2.5% dextrose solution may be given. Insulin treatment is not recommended because the acute decrease in glucose, which lowers plasma osmolality, may precipitate cerebral edema.
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Once the child is urinating, add 40 mEq/L KCl to fluids to aid water absorption into cells.
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Calcium may be added if the patient has an associated low serum calcium level.
Serum sodium levels
Serum sodium levels should be monitored every 4 hours.
Further inpatient care
Inpatient management also includes the following:
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Record daily body weights in patients with hypernatremia.
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Frequently monitor electrolyte concentrations.
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Restrict sodium and protein intake.
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Treat the underlying disease.
Transfer
Patients with symptomatic hypernatremia should be transferred to a pediatric intensive care unit for appropriate treatment and close monitoring.
Patients should be transferred to a facility that has dialysis in case of renal failure or in case the serum sodium concentration is more than 180 mEq/L.
Diet
In diabetes insipidus, a sodium-restricted and protein-restricted diet should be prescribed
Consultations
Consultation is also recommended for patients with renal dysplasia, medullary cystic disease, reflux nephropathy, or polycystic disease. Consider obtaining consultations with the following specialists:
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Critical care specialist: Patients with symptomatic hypernatremia may need to be transferred to a pediatric ICU for appropriate treatment and monitoring.
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Endocrinologist: Consult an endocrinologist for patients with primary hyperaldosteronism.
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Nephrologist: Consult a nephrologist in cases of renal failure, obstructive uropathy, and serum sodium levels of more than 180 mEq/L for possible peritoneal dialysis.
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Pediatric Hypernatremia. Figure A: Normal cell. Figure B: Cell initially responds to extracellular hypertonicity through passive osmosis of water extracellularly, resulting in cell shrinkage. Figure C: Cell actively responds to extracellular hypertonicity and cell shrinkage in order to limit water loss through transport of organic osmolytes across the cell membrane, as well as through intracellular production of these osmolytes. Figure D: Rapid correction of extracellular hypertonicity results in passive movement of water molecules into the relatively hypertonic intracellular space, causing cellular swelling, damage, and ultimately death.
