What is the treatment for polyuria after correction of hyponatremia with 3% Sodium Chloride (NaCl)?

Treatment for Polyuria Post 3% NaCl for Hyponatremia

Polyuria following 3% hypertonic saline correction of hyponatremia represents an aquaresis (water diuresis) that requires immediate intervention with desmopressin to prevent overcorrection and osmotic demyelination syndrome. 1, 2

Immediate Management

Administer desmopressin 1-2 µg parenterally (IV or subcutaneously) every 6-8 hours to halt the water diuresis and prevent overcorrection. 1, 2 This medication blocks the aquaretic response that commonly emerges after hypertonic saline administration, which is the primary cause of inadvertent overcorrection. 2

• Discontinue or reduce the 3% saline infusion immediately when polyuria develops to prevent further sodium increase 1
• Switch to D5W (5% dextrose in water) if sodium has already been overcorrected (>8 mmol/L in 24 hours) to actively relower sodium levels 1

Monitoring Protocol

Check serum sodium every 2 hours during active polyuria until the water diuresis is controlled and sodium stabilization is confirmed. 1 This frequent monitoring is critical because:

• Polyuria can cause sodium to rise by >12 mmol/L in 24 hours, exceeding safe correction limits 2
• The aquaretic response is unpredictable in timing and magnitude 2
• Osmotic demyelination syndrome risk increases dramatically with overcorrection >8 mmol/L per 24 hours 1, 3

Track urine output hourly to assess the effectiveness of desmopressin therapy and adjust dosing accordingly. 2

Target Correction Limits

The total sodium correction must not exceed 8 mmol/L in 24 hours to prevent osmotic demyelination syndrome, regardless of the initial severity of hyponatremia. 1, 3, 4 For high-risk patients (advanced liver disease, alcoholism, malnutrition, or prior encephalopathy), limit correction to 4-6 mmol/L per day. 1

• If sodium has already increased by 6 mmol/L in the first 6 hours, only 2 mmol/L additional correction is permitted in the remaining 18 hours 1
• Do not attempt to normalize sodium to laboratory reference ranges—gradual correction with clinical evaluation is preferable 3

Mechanism and Rationale

The polyuria occurs because:

• Hypertonic saline suppresses endogenous ADH secretion once plasma osmolality increases 5
• The kidneys rapidly excrete the retained free water that accumulated during the hyponatremic state 2
• This aquaresis is often more vigorous than anticipated, leading to overcorrection in 4.5-28% of cases without preventive measures 4, 2

Desmopressin prevents this aquaresis by providing exogenous ADH activity, allowing controlled sodium correction while maintaining the ability to administer additional hypertonic saline if needed. 2 This strategy has been shown to prevent overcorrection without adverse effects when combined with weight-based hypertonic saline dosing. 2

Common Pitfall to Avoid

Never assume polyuria will self-limit—this is the most common cause of iatrogenic overcorrection and osmotic demyelination syndrome. 1, 2 The combination of hypertonic saline plus desmopressin from the outset prevents this complication entirely, with studies showing no overcorrection when this protocol is followed. 2

If overcorrection has already occurred (sodium increased >8 mmol/L in 24 hours), immediately administer D5W and desmopressin to actively relower sodium levels, targeting a reduction to bring the total 24-hour correction to no more than 8 mmol/L from baseline. 1