Treatment of Hypernatremia with 0.45% NaCl
Critical Assessment: This is Inappropriate Therapy
For a serum sodium of 165 mEq/L, administering 0.45% NaCl (half-normal saline) at 60 mL/hr is inappropriate and potentially dangerous. This solution contains 77 mEq/L of sodium, which is still hypertonic relative to the patient's needs and will not effectively correct severe hypernatremia 1.
Correct Fluid Selection for Severe Hypernatremia
Use hypotonic fluids such as 0.18% NaCl (quarter-normal saline with ~31 mEq/L sodium) or D5W (5% dextrose in water) for patients with severe hypernatremia requiring correction 1.
Rationale for Fluid Choice:
- 0.45% NaCl is inadequate because it provides insufficient free water relative to sodium content for a sodium level of 165 mEq/L 1
- 0.18% NaCl or D5W are preferred as they provide greater free water content necessary for correcting severe hypernatremia 1
- Isotonic fluids (0.9% NaCl) will worsen hypernatremia and should be avoided entirely 1
Correction Rate Guidelines
Reduce serum sodium at 10-15 mmol/L per 24 hours to prevent cerebral edema 1. Too rapid correction over less than 48-72 hours increases the risk of pontine myelinolysis 1.
Specific Correction Protocol:
- Calculate water deficit: Use the formula to determine total free water needed
- Distribute correction over 48-72 hours to avoid neurological complications 2, 3
- Monitor serum sodium every 4-6 hours during active correction 4
Special Clinical Scenarios Requiring Hypotonic Fluids
Renal Concentrating Defects:
- Patients with nephrogenic diabetes insipidus require ongoing hypotonic fluid administration to match excessive free water losses 1
- These patients will develop worsening hypernatremia if given isotonic solutions 1
Excessive Fluid Losses:
- Voluminous diarrhea or severe burns require hypotonic fluids to replace free water losses 1
- Match fluid composition to losses while providing adequate free water 1
Monitoring During Correction
Track the following parameters closely:
- Serum sodium every 4-6 hours initially 4
- Neurological status for signs of cerebral edema (confusion, seizures, altered consciousness) 4, 2
- Volume status to avoid pulmonary edema 2
- Urine output and osmolality 4
Common Pitfalls to Avoid
Never use 0.45% NaCl as primary therapy for severe hypernatremia - it contains too much sodium (77 mEq/L) to effectively correct a sodium of 165 mEq/L 1.
Never correct hypernatremia faster than 48-72 hours - rapid correction causes cerebral edema and pontine myelinolysis 1, 2.
Never use isotonic saline (0.9% NaCl) in hypernatremia - this will exacerbate the condition 1.
In salt intoxication cases, add diuretics to prevent pulmonary edema during water replacement 2.