Management of Severe Hypernatremia (162 mmol/L) in a Patient on Furosemide
Immediately discontinue furosemide and initiate free water replacement with hypotonic fluids to correct the hypernatremia, while simultaneously investigating and treating the underlying cause.
Immediate Actions
Stop furosemide immediately – loop diuretics promote free water loss and will worsen hypernatremia 1. The patient's sodium of 162 mmol/L represents severe hypernatremia that requires urgent intervention 1.
Assess volume status and hydration – determine if the patient has pure water deficit (hypovolemic hypernatremia from diuretic-induced free water loss) versus hypervolemic hypernatremia 1, 2. Look specifically for:
- Orthostatic hypotension, tachycardia, dry mucous membranes, decreased skin turgor (hypovolemia) 3
- Peripheral edema, ascites, jugular venous distention (hypervolemia) 3
Check urine osmolality and urine sodium to determine the mechanism 1, 2:
- High urine osmolality (>600-800 mOsm/kg) suggests extrarenal water loss
- Low urine osmolality (<300 mOsm/kg) suggests diabetes insipidus
- Urine sodium helps distinguish renal versus extrarenal losses 1
Fluid Replacement Strategy
Administer hypotonic fluids for correction 4, 1, 2:
- 0.45% NaCl (half-normal saline) is the preferred initial fluid for moderate hypernatremia 3
- D5W (5% dextrose in water) provides pure free water and is preferred for severe hypernatremia or when more aggressive free water replacement is needed 3, 2
- Avoid isotonic saline (0.9% NaCl) – this will worsen hypernatremia as it delivers excessive osmotic load requiring 3 liters of urine to excrete the osmotic load from just 1 liter of fluid 3
Calculate the free water deficit using the formula 4:
- Free water deficit = 0.6 × body weight (kg) × [(current Na ÷ 140) - 1]
- This guides the total volume of hypotonic fluid needed
Critical Correction Rate Guidelines
Do NOT correct faster than 10-12 mmol/L per 24 hours 1, 2:
- For chronic hypernatremia (>48 hours), limit correction to 8-10 mmol/L per day maximum 2
- Rapid correction can cause cerebral edema and seizures 1, 2
- Correction rates faster than 48-72 hours for severe hypernatremia increase the risk of pontine myelinolysis 3
Target correction rate: 0.5 mmol/L per hour or approximately 10-12 mmol/L per day 1, 2.
Monitor serum sodium every 2-4 hours initially during active correction to ensure you stay within safe limits 1, 2.
Addressing the Underlying Cause
Investigate why hypernatremia developed 1, 2:
- Excessive diuretic use (furosemide) causing free water loss
- Inadequate fluid intake or impaired thirst mechanism
- Osmotic diuresis (check glucose for hyperglycemia)
- Diabetes insipidus (central or nephrogenic)
- Gastrointestinal losses (diarrhea, especially lactulose-induced in cirrhotic patients) 5
If diabetes insipidus is suspected, consider desmopressin (DDAVP) administration 2.
Special Considerations
In cirrhotic patients, hypernatremia usually follows hypotonic fluid losses from osmotic diuresis or lactulose-induced diarrhea 5. Prompt recognition and removal of precipitating factors with non-osmotic fluid administration are essential 5.
If the patient has renal concentrating defects (e.g., nephrogenic diabetes insipidus), they will require ongoing hypotonic fluid administration to match excessive free water losses 3.
Avoid fluid restriction – this is contraindicated in hypernatremia and will worsen the condition 1, 2.
Monitoring Protocol
- Serum sodium every 2-4 hours during initial correction phase 1, 2
- Daily weights and strict intake/output monitoring 1
- Neurological examination for signs of cerebral edema (confusion, seizures, altered consciousness) 4, 1
- Urine output and osmolality to assess response 1, 2
Common Pitfalls to Avoid
Never continue furosemide while trying to correct hypernatremia – loop diuretics promote free water excretion and will counteract your correction efforts 1.
Never use isotonic saline for hypernatremia correction – this worsens the condition by delivering excessive sodium load 3.
Never correct too rapidly – exceeding 10-12 mmol/L per day risks cerebral edema, seizures, and permanent neurological damage 1, 2.
Do not ignore the underlying cause – simply correcting the sodium without addressing why it occurred (e.g., continuing diuretics, not treating diabetes insipidus) will lead to recurrence 1, 2.