How can I safely raise serum sodium in an elderly woman with severe symptomatic hyponatraemia (Na 105 mmol/L) and confusion using only isotonic normal saline when hypertonic saline is unavailable?

Emergency Management of Severe Symptomatic Hyponatremia Using Normal Saline When Hypertonic Saline is Unavailable

Critical Limitation: Normal Saline is NOT Appropriate for Severe Symptomatic Hyponatremia

You cannot safely raise serum sodium in a patient with severe symptomatic hyponatremia (Na 105 mmol/L) using isotonic normal saline (0.9% NaCl). Normal saline is hypotonic relative to this patient's serum and will worsen hyponatremia by adding free water. 1, 2

Why Normal Saline Fails in This Clinical Scenario

• Isotonic saline (154 mEq/L sodium) is actually hypotonic compared to the patient's total osmolality when serum sodium is 105 mmol/L 1
• Normal saline will be rapidly distributed throughout total body water, diluting serum sodium further rather than raising it 2
• Severely symptomatic hyponatremia with confusion at Na 105 mmol/L represents a medical emergency requiring hypertonic saline to prevent seizures, coma, brain herniation, and death 1, 2

What Constitutes Appropriate Emergency Treatment

Severely symptomatic hyponatremia (somnolence, obtundation, coma, seizures, confusion, or cardiorespiratory distress) requires bolus hypertonic saline (3% NaCl) to reverse hyponatremic encephalopathy. 2

Evidence-Based Hypertonic Saline Protocol

• Initial bolus: 250 mL of 3% hypertonic saline administered over 15-20 minutes is more effective than 100 mL (52% vs 32% achieving ≥5 mmol/L rise within 4 hours, P=0.018) 3
• Target correction: 4-6 mmol/L increase within 1-2 hours to reverse acute cerebral edema 2, 4
• 24-hour limit: Do not exceed 10 mmol/L correction in the first 24 hours to prevent osmotic demyelination syndrome 2, 4
• Repeat bolus if needed: Can administer additional 250 mL boluses if symptoms persist and sodium has not risen adequately, checking sodium every 2 hours 2, 3

Critical Monitoring Requirements

• Check serum sodium every 2 hours initially during acute correction phase 2
• Monitor urine output closely as diuresis correlates with overcorrection risk (r=0.6, P<0.01) 5
• Stop hypertonic saline once symptoms resolve or target 4-6 mmol/L increase is achieved 2, 4

Alternative Strategies When Hypertonic Saline is Truly Unavailable

If 3% hypertonic saline cannot be obtained through any means, consider these options:

Option 1: Compound Hypertonic Saline On-Site

• Mix 3% hypertonic saline using sterile water or sterile normal saline as diluent in resource-limited settings 6
• To make 1 liter of 3% saline: Add 30 grams of NaCl to sterile water, or mix concentrated saline solutions if available 6

Option 2: Use Hypertonic Sodium Bicarbonate

• Hypertonic sodium bicarbonate achieves sodium loading similar to hypertonic saline through the same mechanism 7
• Target serum sodium should not exceed 150-155 mEq/L to prevent iatrogenic harm 7
• Monitor for hypokalemia, which can complicate alkalemia therapy 7
• This is NOT standard therapy for hyponatremia but represents a physiologically sound alternative when hypertonic saline is unavailable 7

Option 3: Emergency Transfer

• Transfer the patient immediately to a facility with hypertonic saline if the above options are not feasible
• Severe symptomatic hyponatremia at Na 105 mmol/L with confusion represents imminent risk of seizures, coma, and death 1, 2

Common Pitfalls to Avoid

• Never use hypotonic solutions (0.45% saline, Ringer's lactate, 5% dextrose, Hartmann's solution) as these will worsen hyponatremia 6
• Do not delay treatment while pursuing diagnostic workup; treat first, diagnose later 1
• Beware of spontaneous water diuresis after initial treatment, which can cause inadvertent overcorrection; monitor urine output hourly 5, 4
• Administer desmopressin if unwanted water diuresis causes overcorrection beyond 10 mmol/L in 24 hours 4
• Overcorrection occurs in 21-38% of cases depending on symptom severity, with higher risk in severely symptomatic patients 3, 5

Volume Status Considerations After Acute Phase

Once the emergency is stabilized with hypertonic saline and symptoms resolve:

• If hypovolemic hyponatremia: Transition to normal saline infusions for volume repletion 1
• If euvolemic hyponatremia: Implement free water restriction or consider vaptans 1, 2
• If hypervolemic hyponatremia: Treat underlying cause (heart failure, cirrhosis) and restrict free water 1

Normal saline has NO role in the acute emergency management of severe symptomatic hyponatremia but may be appropriate for subsequent volume repletion in hypovolemic patients after the acute crisis is resolved. 1