From the Guidelines
Management of a patient with dehydration and hypernatremia (sodium of 157) requires careful fluid replacement with hypotonic fluids, such as 5% dextrose in water, to correct both conditions while avoiding complications. The goal is to correct the free water deficit and normalize serum sodium levels without causing cerebral edema or osmotic demyelination syndrome. According to the international expert consensus statement on the diagnosis and management of congenital nephrogenic diabetes insipidus 1, the typical emergency in NDI is hypernatraemic dehydration, which should be treated with water, and salt-containing solutions should be avoided.
For initial treatment, calculate the free water deficit using the formula: Free water deficit = 0.6 × body weight (kg) × [(measured Na⁺/140) - 1] 1. The rate of sodium correction should not exceed 10 mEq/L in 24 hours (or 0.5 mEq/L/hour) to prevent cerebral edema and osmotic demyelination syndrome. For severe hypernatremia (>160 mEq/L), slower correction at 8 mEq/L/day is recommended.
Some key points to consider in the management of hypernatremic dehydration include:
- Administering hypotonic fluids, such as 5% dextrose in water, intravenously to correct the free water deficit
- Avoiding salt-containing solutions, such as NaCl 0.9% solutions, due to their large renal osmotic load
- Monitoring serum electrolytes every 2-4 hours initially, then every 4-6 hours as the patient stabilizes
- Maintaining adequate urine output and monitoring for signs of fluid overload
- Transitioning from IV to oral hydration once the patient can take oral fluids
It is essential to note that the use of dextrose 5% solutions does not usually pose a risk of brain edema in patients with NDI, as their urine is diluted with a very low sodium concentration, and the hypotonic intravenous fluid matches the urinary losses 1. However, dextrose 5% solution should not be administered as a bolus due to the risk of a rapid decrease in serum sodium.
In hospitalized patients, close observation of clinical status, including neurological condition, fluid balance, weight, and electrolytes, is recommended 1. Placement of a urinary catheter should be considered to ensure proper monitoring of diuresis. Fluid composition and rate of administration should be adjusted according to the patient's response to treatment.
From the Research
Managing Dehydration and Hypernatremia
To manage a patient with dehydration and hypernatremia, the following steps can be taken:
- Correct the underlying cause of the hypernatremia 2, 3
- Replace the free water deficit with hypotonic infusions 2
- Monitor the patient's volume status and osmolality of urine to guide treatment 2
- Avoid rapid changes in serum sodium concentration to prevent osmotic demyelination syndrome 2, 4, 5
- Consider the use of desmopressin in patients with central diabetes insipidus or essential hypernatremia 6, 4, 5
Treatment Options
Treatment options for hypernatremia include:
- Hypotonic infusions to replace free water deficit 2
- Desmopressin to treat central diabetes insipidus or essential hypernatremia 6
- Hemodialysis to rapidly normalize serum sodium levels in acute hypernatremia 2
- Correction of the underlying cause of the hypernatremia 2, 3
Monitoring and Precautions
When managing a patient with hypernatremia, it is essential to:
- Monitor serum sodium levels closely to avoid overcorrection 2, 4, 5
- Monitor the patient's volume status and osmolality of urine to guide treatment 2
- Avoid rapid changes in serum sodium concentration to prevent osmotic demyelination syndrome 2, 4, 5
- Consider the use of a combination of therapies, such as hypertonic saline and desmopressin, to safely correct severe hyponatremia 5