Management of Severe Hypernatremia (167 mEq/L) with Altered Mental Status in COPD
For your drowsy COPD patient with severe hypernatremia (sodium 167 mEq/L), correct the sodium slowly using hypotonic fluids (0.45% NaCl or D5W) at a maximum rate of 10 mmol/L per 24 hours, targeting a reduction of approximately 0.4 mmol/L per hour. 1
Immediate Assessment
Your patient requires urgent but controlled correction. The drowsiness indicates CNS dysfunction from cellular dehydration, which is a medical emergency requiring ICU-level monitoring 1, 2. However, rapid correction in chronic hypernatremia (which this likely is given the severity) can cause cerebral edema and death 3.
Determine Acuity
- If hypernatremia developed over >48 hours (chronic): Correct slowly at ≤0.4 mmol/L per hour (maximum 10 mmol/L per 24 hours) 1
- If hypernatremia developed acutely (<48 hours): Faster correction improves prognosis, but this is unlikely given the severity 1
- In COPD patients with altered mental status and sodium 167 mEq/L, assume chronic hypernatremia unless you have clear evidence of acute development 1, 2
Fluid Selection and Administration
Use hypotonic fluids as your primary correction strategy:
- First-line: 0.45% NaCl (half-normal saline) provides both free water and some sodium replacement 1
- Alternative: D5W (5% dextrose in water) for more aggressive free water replacement if the patient has pure water deficit 1
- Avoid isotonic saline (0.9% NaCl) as this will worsen hypernatremia in patients unable to excrete sodium appropriately 1, 2
Calculate Free Water Deficit
Free water deficit = 0.6 × body weight (kg) × [(current Na ÷ 140) - 1]
This tells you the total volume needed, but replace this deficit slowly over 48-72 hours minimum 1, 3.
Correction Rate: The Critical Safety Parameter
Maximum correction: 10 mmol/L per 24 hours (approximately 0.4 mmol/L per hour) 1
For your patient with sodium 167 mEq/L:
- Day 1 target: Reduce to approximately 157 mEq/L
- Day 2 target: Reduce to approximately 147 mEq/L
- Day 3 target: Approach normal range (135-145 mEq/L)
Faster correction risks cerebral edema, seizures, permanent neurologic damage, and death 3, 4. Even though recent data in ICU patients showed no increased mortality with faster correction rates 4, the traditional conservative approach remains safer for chronic hypernatremia, especially with CNS symptoms 1, 3.
Monitoring Protocol
Check sodium every 2-4 hours during active correction 1, 2:
- If sodium drops too quickly (>0.5 mmol/L per hour), slow or temporarily stop hypotonic fluids
- If sodium drops too slowly, increase infusion rate slightly
- Monitor mental status closely—improvement should parallel sodium correction
Additional monitoring:
- Urine output and osmolality to assess ongoing losses 1
- Volume status (avoid fluid overload in COPD patients) 2
- Neurologic examination for signs of cerebral edema (worsening mental status, seizures) 3
Address Underlying Cause
In COPD patients, hypernatremia commonly results from:
- Insensible losses from tachypnea and increased respiratory effort 2
- Inadequate fluid intake due to dyspnea or altered mental status 1
- Diuretic use for cor pulmonale 2
Ensure adequate ongoing fluid intake matches losses once initial correction is achieved 1.
Special COPD Considerations
- Avoid fluid overload: COPD patients may have right heart dysfunction; monitor for peripheral edema and worsening respiratory status 2
- Oxygen supplementation: Maintain adequate oxygenation during correction 2
- Consider non-invasive ventilation if respiratory distress worsens with fluid administration 2
Common Pitfalls
- Correcting too rapidly (>0.5 mmol/L per hour) risks cerebral edema in chronic hypernatremia 1, 3
- Using isotonic saline will worsen hypernatremia in patients with impaired free water excretion 1
- Failing to monitor frequently during active correction can lead to overcorrection 2
- Not addressing ongoing losses (insensible losses from tachypnea) will prevent adequate correction 1, 2