Is NaCl (normal saline) 0.9% okay for an elderly patient with altered mental status, hyponatremia, and hyperglycemia who has shown improvement after initial treatment?

Normal Saline (0.9% NaCl) is Contraindicated in Hypernatremia

No, NaCl 0.9% is absolutely not appropriate for this elderly patient with hypernatremia and hyperglycemia. Normal saline will paradoxically worsen hypernatremia because it delivers an excessive osmotic load—its tonicity is approximately 3-fold higher than typical urine osmolality in hypernatremic states 1.

Why Normal Saline Worsens Hypernatremia

• The American College of Nephrology explicitly warns against using 0.9% NaCl as primary fluid in hypernatremic dehydration, as salt-containing solutions have a tonicity that is approximately 3-fold higher than typical urine osmolality in hypernatremic states 1
• Normal saline provides excessive osmotic load that the kidneys cannot adequately excrete in hypernatremic conditions 1
• This patient's hyperglycemia from hyperosmolar hyperglycemic syndrome (HHS) has already caused osmotic diuresis-induced water loss exceeding sodium loss 2

Correct Fluid Choice: D5W (5% Dextrose in Water)

The American College of Nephrology recommends using 5% dextrose in water (D5W) as the primary IV fluid for hypernatremic dehydration 1. Here's why:

• D5W delivers no renal osmotic load, allowing controlled correction of water deficit without adding additional sodium burden 1
• The dextrose is rapidly metabolized, leaving free water to correct the hypernatremia 1
• This approach directly addresses the pathophysiology: water loss exceeding sodium loss 2

Calculating D5W Requirements

For this patient, calculate the water deficit using 1:

• Water deficit = Total body water × [(Current Na⁺/Desired Na⁺) - 1]
• Total body water (TBW) = 0.6 × weight in kg for adult males 1
• The total D5W needed equals the calculated water deficit 1

Administration Protocol

• Initial D5W rate = Total volume ÷ 48 hours (e.g., 6.1 L ÷ 48 hours = 127 mL/hour) 1
• Critical safety limit: Correction rate must not exceed 8-10 mEq/L/day to prevent cerebral edema 1
• The induced change in serum osmolality should not exceed 3 mOsm/kg H₂O per hour 1

Essential Monitoring

• Monitor serum sodium every 4-6 hours during initial correction and adjust D5W rate based on measurements 1
• Assess volume status regularly through hemodynamic monitoring, input/output measurements, and clinical examination for fluid overload 1
• If renal or cardiac compromise exists, more frequent monitoring of serum osmolality and mental status is required 1
• Continue monitoring until osmolality normalizes to <300 mOsm/kg 1

Concurrent Electrolyte Management

• Address potassium abnormalities concurrently with sodium correction 1
• Once renal function is assured, add 20-30 mEq/L potassium to IV fluids (2/3 KCl and 1/3 KPO4) as hypernatremia often coexists with potassium depletion 1
• This patient's initial hypokalemia (K 3.2 mEq/L) requires correction alongside sodium management 3

Critical Pitfall to Avoid

The single most dangerous error is using 0.9% NaCl as primary fluid 1. This mistake occurs because clinicians reflexively reach for "normal" saline without recognizing that its sodium content (154 mEq/L) far exceeds what hypernatremic patients need. The case report of successful recovery from extreme hypernatremia emphasizes that judicious fluid replacement with appropriate hypotonic solutions is essential 2.

Special Consideration for This Patient

Given the patient's altered mental status and hyperglycemia, this likely represents hyperosmolar hyperglycemic state (HHS) 2, 4. The abnormal mental status may include reversible electroencephalogram changes that resolve with appropriate fluid therapy 2. Gradual replacement of sodium and water deficits (maximal reduction in osmolality 3 mOsm/kg H₂O/h) helps prevent cerebral edema 1.