How to manage persistent hypernatremia in a patient with improving renal function and a calculated free water deficit of approximately 2 liters, currently being treated with 50 ml/hour of D5W?

Persistent Hypernatremia Despite D5W Correction

Your sodium correction is slower than expected because D5W at 50 ml/hour provides insufficient free water replacement for a 2-liter deficit, and ongoing insensible losses plus any continued renal free water loss are competing with your correction efforts. 1, 2

Why Sodium Isn't Correcting as Expected

Inadequate Free Water Delivery Rate

• D5W at 50 ml/hour delivers only 1.2 liters of free water per 24 hours (50 ml/hr × 24 hours = 1,200 ml), which is insufficient when you have a calculated 2-liter free water deficit 1, 2
• At this rate, it would take approximately 40 hours to replace the deficit, assuming no ongoing losses 2
• The maximum safe correction rate for hypernatremia is 10-15 mEq/L per 24 hours, but your current rate may be too conservative given the persistent elevation 3

Competing Ongoing Losses

• Insensible losses alone account for 800-1,000 ml/day in adults, which your current D5W rate barely covers 1
• If the patient has any degree of diabetes insipidus, nephrogenic concentrating defects, or ongoing osmotic diuresis, additional free water losses will prevent correction 2
• Improving renal function (creatinine 1.11 from higher baseline) may paradoxically increase free water clearance if there's underlying concentrating defect 2

Recommended Management Adjustments

Increase D5W Infusion Rate

• Increase D5W to 75-100 ml/hour to provide 1.8-2.4 liters of free water per 24 hours, accounting for both deficit replacement and ongoing losses 1, 2
• This rate allows correction of 8-12 mEq/L per 24 hours while covering insensible losses 3, 1
• Monitor sodium every 4-6 hours initially to ensure correction doesn't exceed 10-15 mEq/L per 24 hours 3

Calculate Precise Free Water Deficit

• Recalculate free water deficit using current sodium of 156 mEq/L: Free water deficit = 0.6 × body weight (kg) × [(current Na - 140)/140] 1, 2
• Add 1-1.5 liters to account for ongoing insensible and renal losses over the correction period 1
• Divide total replacement volume by 48-72 hours for safe correction timeline 2

Address Underlying Causes

• Evaluate for ongoing free water losses: Check urine osmolality and urine output to identify diabetes insipidus or osmotic diuresis 2
• If urine osmolality is inappropriately low (<300 mOsm/kg) with hypernatremia, consider central or nephrogenic diabetes insipidus requiring specific treatment 2
• Ensure adequate oral intake if patient is alert: Free water by mouth is preferable to IV when feasible 1

Critical Monitoring Parameters

Sodium Correction Rate

• Check sodium every 4-6 hours during active correction to prevent overcorrection 3, 1
• Target reduction of 0.5 mEq/L per hour or 10-12 mEq/L per 24 hours maximum 3, 2
• If correction exceeds 12 mEq/L in 24 hours, reduce D5W rate by 25-50% 3

Volume Status and Renal Function

• Monitor daily weights and fluid balance to ensure adequate hydration without volume overload 1
• Continue tracking BUN and creatinine to assess renal response 2
• Watch for signs of cerebral edema if correction is too rapid: headache, altered mental status, seizures 2

Common Pitfalls to Avoid

• Don't assume calculated deficit equals actual replacement needs - ongoing losses require additional free water beyond the initial deficit 1, 2
• Don't maintain the same D5W rate if sodium isn't responding - reassess and increase rate if correction is inadequate after 12-24 hours 1
• Don't correct hypernatremia faster than 48-72 hours in chronic cases - rapid correction risks cerebral edema, particularly in vulnerable populations 2
• Don't ignore underlying causes - persistent hypernatremia despite adequate free water suggests ongoing pathologic losses requiring specific treatment 2