How often should serum sodium be checked during correction of hyponatremia, particularly when using hypertonic saline or rapid‑infusion protocols?

Frequency of Serum Sodium Monitoring During Hyponatremia Correction

For severe symptomatic hyponatremia requiring hypertonic saline, check serum sodium every 2 hours during the initial correction phase until symptoms resolve, then transition to every 4 hours. 1, 2

Monitoring Protocol Based on Symptom Severity

Severe Symptomatic Hyponatremia (Seizures, Coma, Altered Mental Status)

• Check serum sodium every 2 hours during active correction with 3% hypertonic saline until severe symptoms resolve or the initial 6 mmol/L correction target is achieved 1, 2
• Once severe symptoms resolve, transition to checking every 4 hours for the remainder of the first 24 hours 1, 2
• After the first 24 hours, continue monitoring every 4–6 hours until the correction is complete and sodium stabilizes 1

Mild to Moderate Symptomatic or Asymptomatic Hyponatremia

• Check serum sodium every 4 hours initially during active correction 1, 3
• After stabilization, transition to daily monitoring once the correction rate is controlled 1

Critical Safety Checkpoints

First 24 Hours

• The absolute maximum correction is 8 mmol/L in any 24-hour period to prevent osmotic demyelination syndrome 1, 3, 4
• For high-risk patients (advanced liver disease, alcoholism, malnutrition), limit correction to 4–6 mmol/L per day 1
• If using 3% hypertonic saline boluses, recheck sodium within 4–6 hours after each bolus to guide whether additional doses are needed 5, 6, 7

Monitoring for Overcorrection

• Watch for sudden decreases in urine specific gravity (≥0.010 from baseline), which signals water diuresis and risk of overcorrection 8
• If water diuresis is detected, immediately recheck serum sodium and consider desmopressin to prevent further rapid correction 9, 8
• Overcorrection typically occurs after a median of 13 hours (range 9–17 hours), so heightened vigilance is needed during this window 7

Special Populations Requiring More Frequent Monitoring

Cirrhotic Patients

• Check sodium every 2 hours during initial correction due to exceptionally high risk of osmotic demyelination 1
• Target correction of only 4–6 mmol/L per day with absolute maximum of 8 mmol/L in 24 hours 5, 1

Neurosurgical Patients (Cerebral Salt Wasting)

• Monitor every 2 hours during severe symptomatic correction with volume and sodium replacement 1
• Distinguish from SIADH, as treatment approaches differ fundamentally 1

Practical Monitoring Algorithm

Hour 0–6 (Initial Correction Phase):

• Severe symptoms: every 2 hours 1, 2
• Mild symptoms: every 4 hours 1, 3

Hour 6–24 (Stabilization Phase):

• After symptom resolution: every 4 hours 1, 2
• Continue until 24-hour correction limit confirmed 1

After 24 Hours:

• Every 4–6 hours if correction ongoing 1
• Daily once stable 1

Common Pitfalls to Avoid

• Inadequate monitoring frequency is a major cause of overcorrection and osmotic demyelination syndrome 1
• Do not rely on scheduled monitoring alone—recheck immediately if urine output suddenly increases or urine specific gravity drops 8
• Never exceed 8 mmol/L correction in 24 hours, even if symptoms persist, except in confirmed acute hyponatremia (<48 hours duration) 1, 3, 4
• Failing to monitor more frequently in high-risk patients (cirrhosis, alcoholism, malnutrition) increases demyelination risk 1