Should an elderly patient with hyponatremia (sodium level 115 mmol/L), who is experiencing restlessness and has been started on normal saline (0.9% NaCl), be switched to 3% hypertonic saline (3% NaCl)?

Should 3% Hypertonic Saline Be Started?

Yes, this elderly patient with severe symptomatic hyponatremia (sodium 115 mmol/L) and new-onset restlessness should be switched from normal saline to 3% hypertonic saline immediately. The restlessness represents a neurological symptom indicating hyponatremic encephalopathy, which is a medical emergency requiring urgent treatment with hypertonic saline 1, 2.

Why Normal Saline Has Failed

Normal saline (0.9% NaCl) is inappropriate for this patient's severe hyponatremia and may actually be worsening the condition 1. When the sum of urinary sodium and potassium concentrations exceeds the plasma sodium concentration, normal saline can paradoxically lower serum sodium further because the kidneys excrete the infused sodium while retaining free water 3. For patients with worsening hyponatremia on normal saline, the Neurosurgery society recommends discontinuing normal saline and switching to 3% hypertonic saline for severe symptoms 1.

Immediate Treatment Protocol

Initial Bolus Administration

• Administer 100 mL of 3% hypertonic saline IV over 10 minutes immediately 2, 4
• This can be repeated every 10 minutes if restlessness persists, up to three total boluses 2
• Target an initial sodium increase of 4-6 mEq/L in the first hour to abort severe symptoms 2, 5

Correction Rate Guidelines

• Correct sodium by 6 mmol/L over the first 6 hours or until symptoms (restlessness) resolve 1, 2
• Maximum total correction must not exceed 8 mmol/L in 24 hours to prevent osmotic demyelination syndrome 1, 2, 5
• If 6 mmol/L is corrected in the first 6 hours, limit correction to only 2 mmol/L in the following 18 hours 2

Monitoring Requirements

Frequent Sodium Checks

• Check serum sodium every 2 hours during initial correction phase 1, 2
• After severe symptoms resolve, check every 4 hours 1
• Monitor strict intake and output 2

Watch for Overcorrection

• If sodium correction exceeds 8 mmol/L in 24 hours, immediately discontinue hypertonic saline and switch to D5W (5% dextrose in water) 1
• Consider administering desmopressin to slow or reverse rapid rise 1, 5
• Signs of osmotic demyelination syndrome include dysarthria, dysphagia, oculomotor dysfunction, and quadriparesis, typically occurring 2-7 days after rapid correction 1, 2

Special Considerations for Elderly Patients

This elderly patient with recent bereavement and poor intake likely has hypovolemic hyponatremia 1. However, the development of restlessness while on normal saline suggests either:

• The patient has SIADH (where normal saline worsens hyponatremia) 1
• The hyponatremia is severe enough that even appropriate volume repletion cannot correct it fast enough 1

High-Risk Population Alert

Elderly patients with poor nutritional intake are at higher risk for osmotic demyelination syndrome and require even more cautious correction (4-6 mmol/L per day) after the initial emergency phase 1, 5. The maximum correction should not exceed 8 mmol/L in 24 hours for this patient 1.

Peripheral IV Administration

3% hypertonic saline can be safely administered through a peripheral IV 4. The misconception that it requires central access is a barrier to appropriate treatment 4. However, monitor the IV site closely for infiltration 4.

Determining Underlying Cause During Treatment

While treating the acute emergency, assess:

• Serum and urine osmolality 1, 2
• Urine sodium concentration (>20 mmol/L suggests SIADH or cerebral salt wasting; <30 mmol/L suggests hypovolemia) 1
• Extracellular fluid volume status (assess for orthostatic hypotension, dry mucous membranes, skin turgor) 1, 2
• Serum uric acid (<4 mg/dL suggests SIADH) 1

Post-Acute Management

Once sodium reaches 120-125 mmol/L and symptoms resolve:

• If hypovolemic: continue isotonic saline for volume repletion 1
• If SIADH: implement fluid restriction to 1 L/day 1, 2
• If hypervolemic: fluid restriction to 1-1.5 L/day 1

Critical Pitfalls to Avoid

• Never use fluid restriction in a patient with true volume depletion 1, 2
• Never delay hypertonic saline for symptomatic severe hyponatremia 6, 4
• Never correct chronic hyponatremia faster than 8 mmol/L in 24 hours 1, 2, 5
• Never ignore mild symptoms like restlessness—they can rapidly progress to seizures and death 6, 4

The restlessness in this patient represents early hyponatremic encephalopathy, which can rapidly progress to seizures, coma, and death from transtentorial herniation 4. Immediate treatment with 3% hypertonic saline is both indicated and potentially life-saving 2, 4.