In an elderly patient with mild hyponatraemia (serum sodium 128 mmol/L), can I prescribe oral sodium chloride 1 g twice daily and re‑check the serum sodium after one week?

Management of Mild Hyponatremia in an Elderly Patient (Serum Sodium 128 mmol/L)

For an elderly patient with serum sodium of 128 mmol/L, oral sodium chloride 1 g twice daily is NOT the appropriate first-line approach—you must first determine the patient's volume status (hypovolemic, euvolemic, or hypervolemic) to guide treatment, and rechecking sodium after one week is too infrequent for safe monitoring.

Initial Assessment Required Before Treatment

Before prescribing any sodium supplementation, you need to establish:

• Volume status through physical examination: look for orthostatic hypotension, dry mucous membranes, decreased skin turgor (hypovolemic); peripheral edema, ascites, jugular venous distention (hypervolemic); or absence of these findings (euvolemic) 1
• Urine sodium concentration: values <30 mmol/L suggest hypovolemic hyponatremia responsive to saline; >20-40 mmol/L with high urine osmolality suggests SIADH 1
• Medication review: diuretics, SSRIs, carbamazepine, NSAIDs, and opioids are common culprits 1
• Symptom assessment: even mild hyponatremia at 128 mmol/L is associated with increased fall risk (21% vs 5% in normonatremic patients) and cognitive impairment 1, 2

Treatment Algorithm Based on Volume Status

If Hypovolemic (True Volume Depletion)

• Administer isotonic saline (0.9% NaCl) for volume repletion, starting at 15-20 mL/kg/h initially, then 4-14 mL/kg/h based on response 1
• Discontinue any diuretics immediately if sodium <125 mmol/L 1
• Oral salt tablets are NOT appropriate for acute hypovolemic hyponatremia—intravenous fluids are required 1

If Euvolemic (Likely SIADH)

• First-line therapy is fluid restriction to 1 L/day (or <800 mL/day for refractory cases), NOT salt tablets 1, 2
• If fluid restriction fails after 48-72 hours, then consider adding oral sodium chloride 100 mEq (approximately 6 g) three times daily—NOT 1 g twice daily 1
• Each 1 gram of sodium chloride contains only 17 mEq of sodium, making your proposed dose of 1 g BID (34 mEq total) inadequate 3, 4
• Alternative second-line options include urea or vaptans (tolvaptan 15 mg daily) 2, 5

If Hypervolemic (Heart Failure, Cirrhosis)

• Implement fluid restriction to 1-1.5 L/day for sodium <125 mmol/L 1
• Continue diuretics with close monitoring when sodium is 126-135 mmol/L and renal function is normal 1, 6
• Avoid salt tablets entirely—they worsen fluid overload in hypervolemic states 1
• For cirrhosis, consider albumin infusion alongside fluid restriction 1

Critical Monitoring Requirements

Rechecking sodium after one week is dangerously inadequate. The correct monitoring schedule is:

• Check serum sodium every 24-48 hours initially when starting any treatment for mild asymptomatic hyponatremia 1, 7
• Never exceed correction of 8 mmol/L in any 24-hour period to prevent osmotic demyelination syndrome 1, 2
• For elderly patients with risk factors (malnutrition, alcoholism, liver disease), limit correction to 4-6 mmol/L per day 1

Why Your Proposed Regimen Is Problematic

• 1 g NaCl twice daily provides only 34 mEq sodium total—this is far below the 100 mEq three times daily (300 mEq total) recommended for SIADH refractory to fluid restriction 1, 4
• Salt tablets are contraindicated in hypervolemic hyponatremia (heart failure, cirrhosis) as they worsen edema and ascites 1
• Weekly sodium monitoring is too infrequent—you risk missing dangerous overcorrection or undercorrection 1, 7
• Salt tablets should never be first-line therapy—fluid restriction or volume repletion (depending on volume status) must be attempted first 1, 2, 5

Correct Approach for This Patient

1. Assess volume status clinically and check urine sodium 1, 7
2. For euvolemic hyponatremia (SIADH): start fluid restriction to 1 L/day 1, 2
3. If fluid restriction fails after 48-72 hours: add oral NaCl 100 mEq (6 g) three times daily OR consider urea/vaptans 1, 2, 5
4. Monitor serum sodium every 24-48 hours, not weekly 1, 7
5. Target correction of 4-6 mmol/L per day, maximum 8 mmol/L in 24 hours 1, 2

Common Pitfalls to Avoid

• Do not prescribe salt tablets without determining volume status—they can be harmful in hypervolemic states 1
• Do not use inadequate salt doses (1 g BID)—if salt supplementation is indicated, use 100 mEq (6 g) three times daily 1, 4
• Do not monitor sodium weekly—this interval is too long and risks complications 1, 7
• Do not skip fluid restriction as first-line therapy for euvolemic hyponatremia 1, 2, 5
• Do not ignore the 8 mmol/L/24-hour correction limit—elderly patients are at high risk for osmotic demyelination syndrome 1, 2