Management of Severe Hypernatremia (Serum Sodium >160 mEq/L)
For severe hypernatremia (>160 mEq/L), administer hypotonic fluids such as 5% dextrose in water (D5W) or 0.45% NaCl, with a maximum correction rate of 0.4 mmol/L/hour or 10 mmol/L per 24 hours to prevent cerebral edema. 1
Initial Assessment and Fluid Selection
D5W (5% dextrose in water) is the preferred first-line rehydration fluid because it delivers no renal osmotic load and allows controlled, gradual decrease in plasma osmolality 1
0.45% NaCl (half-normal saline) is an alternative hypotonic option containing 77 mEq/L sodium with osmolarity of approximately 154 mOsm/L, appropriate for moderate hypernatremia correction 2
Avoid isotonic saline (0.9% NaCl) entirely in hypernatremic dehydration as it delivers excessive osmotic load—requiring 3 liters of urine to excrete the osmotic load from just 1 liter of isotonic fluid, which risks worsening hypernatremia 2
Critical Correction Rate Guidelines
Never exceed 8-10 mmol/L correction per 24 hours for chronic hypernatremia (>48 hours duration) to prevent osmotic demyelination syndrome 1
The maximum safe correction rate is 0.4 mmol/L/hour, which translates to approximately 10 mmol/L per day 1
Rapid changes in serum sodium concentration may cause osmotic demyelination syndrome, making close laboratory monitoring essential 1
Initial Fluid Administration Rates
For adults, start with 25-30 mL/kg/24 hours as the initial fluid administration rate 2
For children, calculate physiological maintenance requirements: 100 mL/kg/24 hours for the first 10 kg, 50 mL/kg/24 hours for 10-20 kg, and 20 mL/kg/24 hours for remaining weight 2
High-risk populations (infants, malnourished patients) may benefit from smaller-volume frequent boluses (10 mL/kg) due to reduced cardiac output capacity 2
Special Clinical Scenarios
Nephrogenic Diabetes Insipidus
Patients with renal concentrating defects require ongoing hypotonic fluid administration to match excessive free water losses 2
Isotonic fluids will worsen hypernatremia in these patients and must be avoided 2
Acute vs. Chronic Hypernatremia
For acute hypernatremia (<24 hours), hemodialysis is an effective option to rapidly normalize serum sodium levels 1
When starting renal replacement therapy in patients with chronic hypernatremia, avoid rapid sodium drops by careful dialysate selection 1
Underlying Cause Management
Address excessive water loss (diarrhea, vomiting) by replacing ongoing losses in addition to correcting the existing deficit 2
Ensure access to free water for patients with inadequate fluid intake as a primary intervention 2
For diabetes insipidus, administer Desmopressin (Minirin) in addition to hypotonic fluid replacement 1
Monitoring Protocol
Check serum sodium every 4-6 hours during active correction to ensure adherence to safe correction rates 1
Monitor for signs of cerebral edema: confusion, headache, seizures, or altered mental status during correction 1
Track urine output and osmolality to assess response to therapy and guide ongoing fluid selection 1
Measure volume status clinically (orthostatic vital signs, skin turgor, mucous membranes) to guide fluid administration rate 2
Common Pitfalls to Avoid
Never correct chronic hypernatremia faster than 10 mmol/L per day—this causes cerebral edema and neurological complications 1
Do not use isotonic saline in hypernatremic patients—it provides insufficient free water and can paradoxically worsen hypernatremia 2, 1
Avoid switching to isotonic fluids prematurely before serum sodium normalizes, as this halts correction 2
Do not neglect ongoing losses—patients with continued diarrhea or polyuria require additional free water beyond calculated deficits 2