Management of Hypernatremia of 160 mmol/L
For severe hypernatremia at 160 mmol/L, immediately initiate hypotonic fluid replacement with 5% dextrose in water (D5W) or 0.45% NaCl, targeting a correction rate no faster than 0.4 mmol/L/hour or 10 mmol/L per 24 hours to prevent cerebral edema. 1, 2
Initial Assessment and Fluid Selection
The primary goal is restoration of plasma tonicity through controlled free water replacement. 2 The choice of hypotonic fluid depends on severity and clinical context:
- D5W (5% dextrose in water) is the preferred initial fluid because it delivers no renal osmotic load and allows slow, controlled decrease in plasma osmolality 1
- 0.45% NaCl (half-normal saline, 77 mEq/L sodium) is appropriate for moderate hypernatremia correction, providing both free water and some sodium replacement 1
- 0.18% NaCl (quarter-normal saline, 31 mEq/L sodium) may be used for more aggressive free water replacement 1
Critical pitfall: Never use isotonic saline (0.9% NaCl) in hypernatremic patients, 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 1
Correction Rate Guidelines
The correction rate must not exceed 0.4 mmol/L/hour or 10 mmol/L per 24 hours for chronic hypernatremia (>48 hours duration). 2, 3 This cautious approach prevents osmotic demyelination syndrome and cerebral edema from rapid osmotic shifts 3
For acute hypernatremia (<24-48 hours), rapid correction improves prognosis by preventing cellular dehydration effects, but still requires monitoring 2
If hypernatremia developed slowly over days, limit correction to no more than 8-10 mmol/L per day. 3
Initial Fluid Administration Rates
Calculate maintenance fluid requirements:
- Adults: 25-30 mL/kg/24 hours 1
- Children: 100 mL/kg/24h for first 10 kg, 50 mL/kg/24h for 10-20 kg, 20 mL/kg/24h for remaining weight 1
Special Clinical Scenarios
Hyperglycemic States (DKA/HHS)
When hypernatremia coexists with severe hyperglycemia, calculate corrected sodium (add 1.6 mEq/L for each 100 mg/dL glucose >100 mg/dL) to determine true severity 4
In combined DKA/HHS with hypernatremia:
- Start insulin drip per DKA protocol initially 4
- Once glucose approaches 300 mg/dL, switch to D5W and Ringer's lactate 4
- Consider desmopressin and free water via nasogastric tube for severe cases with corrected sodium >190 mEq/L 4
Diabetes Insipidus
For central diabetes insipidus: administer desmopressin (Minirin) in addition to hypotonic fluid replacement 3
For nephrogenic diabetes insipidus: Ongoing hypotonic fluid administration is required to match excessive free water losses; isotonic fluids will worsen hypernatremia 1
Hypervolemic Hypernatremia
If hypernatremia results from excessive sodium intake (hypertonic NaCl/NaHCO3 solutions), address the source and consider diuretics alongside hypotonic fluid replacement 2
Monitoring Protocol
- Check serum sodium every 2-4 hours during active correction 1
- Monitor serum osmolality every 6 hours 5
- Track urine output and osmolality to assess underlying cause (diabetes insipidus vs. renal losses) 2
- Assess volume status continuously (orthostatic vitals, mucous membranes, skin turgor) 1
Common Pitfalls to Avoid
- Never correct chronic hypernatremia faster than 10 mmol/L per 24 hours—rapid correction causes cerebral edema 2, 3
- Avoid isotonic saline in hypernatremic patients—it worsens the condition 1
- When initiating renal replacement therapy in chronic hypernatremia, use caution—rapid sodium drops during dialysis can be harmful 3
- For acute severe hypernatremia (<24 hours), hemodialysis is an effective option to rapidly normalize sodium levels 3
Underlying Cause Management
Address the root cause simultaneously: