Treatment for Hypernatremia
For hypernatremia, administer hypotonic fluids (0.45% NaCl or D5W) to replace free water deficit, with a maximum correction rate of 10-15 mmol/L per 24 hours to prevent cerebral edema. 1
Initial Assessment and Fluid Selection
The cornerstone of hypernatremia treatment is identifying whether the patient is hypovolemic, euvolemic, or hypervolemic, as this determines the specific approach 1, 2.
Hypotonic fluids are the primary treatment for most cases of hypernatremia:
- 0.45% NaCl (half-normal saline) contains 77 mEq/L sodium with osmolarity ~154 mOsm/L, appropriate for moderate hypernatremia 1
- 0.18% NaCl (quarter-normal saline) contains ~31 mEq/L sodium, providing more aggressive free water replacement for severe cases 1
- D5W (5% dextrose in water) delivers no renal osmotic load and allows controlled decrease in plasma osmolality 1
Never use isotonic saline (0.9% NaCl) as initial therapy—this will worsen hypernatremia, especially in patients with nephrogenic diabetes insipidus or renal concentrating defects. 1 Isotonic saline delivers excessive osmotic load, requiring 3 liters of urine to excrete the osmotic load from just 1 liter of fluid 1.
Critical Correction Rate Guidelines
The maximum correction rate is 10-15 mmol/L per 24 hours for chronic hypernatremia (>48 hours duration). 1 Correcting chronic hypernatremia too rapidly causes cerebral edema, seizures, and permanent neurological injury because brain cells synthesize intracellular osmolytes over 48 hours to adapt to hyperosmolar conditions 1.
For acute hypernatremia (<48 hours), correction can proceed more rapidly—up to 1 mmol/L/hour if severely symptomatic 1. However, corrections faster than 48-72 hours have been associated with increased risk of pontine myelinolysis 1.
Treatment Based on Volume Status
Hypovolemic Hypernatremia
Administer hypotonic fluids at an initial rate of 4-14 mL/kg/h to replace free water deficit. 1 This is the most common scenario, often resulting from dehydration with impaired thirst mechanism or lack of access to water 2.
For patients with severe burns or voluminous diarrhea, hypotonic fluids must match ongoing free water losses while providing adequate free water replacement 1.
Euvolemic Hypernatremia
Implement a low salt diet (<6 g/day) and protein restriction (<1 g/kg/day). 1 For patients with nephrogenic diabetes insipidus, ongoing hypotonic fluid administration is required to match excessive free water losses 1.
Hypervolemic Hypernatremia
In cirrhotic patients, discontinue intravenous fluid therapy and implement free water restriction, focusing on negative water balance rather than aggressive fluid administration. 1 For heart failure patients, sodium and fluid restriction is essential, limiting fluid intake to around 2 L/day 1.
Special Clinical Scenarios
Severe Symptomatic Hypernatremia
For patients with altered mental status, combine IV hypotonic fluids with free water via nasogastric tube, targeting 10-15 mmol/L correction per 24 hours. 1 In heart failure patients, fluid restriction (1.5-2 L/day) may be needed after initial correction 1.
Nephrogenic Diabetes Insipidus
These patients require ongoing hypotonic fluid administration to match excessive free water losses—isotonic fluids will cause or worsen hypernatremia. 1 Desmopressin should not be used for nephrogenic DI 1.
Traumatic Brain Injury
Prolonged induced hypernatremia to control intracranial pressure is NOT recommended, as it requires an intact blood-brain barrier and may worsen cerebral contusions. 1 There is risk of "rebound" ICP elevation during correction as brain cells synthesize intracellular osmolytes 1.
Monitoring Protocol
Check serum sodium levels every 2-4 hours initially during active correction, then every 6-12 hours. 1 Daily monitoring should include:
- Serum electrolytes and weight 1
- Fluid input and output with careful tracking 1
- Urine output, specific gravity/osmolarity, and urine electrolyte concentrations 1
- Supine and standing vital signs 1
- Renal function (BUN, creatinine) to evaluate for worsening azotemia 1
Common Pitfalls to Avoid
Correcting chronic hypernatremia too rapidly leads to cerebral edema, seizures, and neurological injury—never exceed 10-15 mmol/L per 24 hours. 1 Inadequate monitoring during correction results in overcorrection or undercorrection 1.
Failing to identify and treat the underlying cause is critical, as hypernatremia is often iatrogenic, especially in vulnerable populations. 1 Hospital-acquired hypernatremia is usually preventable with adequate water prescription 3.
In older adults, cognitive impairment may prevent recognition of thirst or ability to access fluids, and reduced renal function affects sodium and water handling 1. These patients require more conservative fluid rates and close monitoring for worsening azotemia 1.