What is the recommended correction protocol for an asymptomatic 60‑year‑old woman with severe hyponatraemia (serum sodium 106 mmol/L)?

Management of Severe Asymptomatic Hyponatremia (Sodium 106 mmol/L)

For a 60-year-old asymptomatic woman with severe hyponatremia (sodium 106 mmol/L), initiate cautious correction with isotonic saline or fluid restriction based on volume status, targeting a maximum increase of 4-6 mmol/L in the first 24 hours, with an absolute ceiling of 8 mmol/L per day to prevent osmotic demyelination syndrome.

Initial Assessment and Diagnostic Workup

Before initiating treatment, rapidly assess the following critical parameters:

• Volume status determination through physical examination looking specifically for orthostatic hypotension, dry mucous membranes, decreased skin turgor (hypovolemia), versus peripheral edema, ascites, jugular venous distention (hypervolemia), versus absence of both (euvolemia) 1

• Obtain serum and urine osmolality, urine sodium concentration, urine electrolytes, and serum uric acid to determine the underlying etiology 1

• Check thyroid-stimulating hormone (TSH) and morning cortisol to exclude hypothyroidism and adrenal insufficiency, which must be ruled out before confirming other diagnoses 1

• Urinary sodium <30 mmol/L** has a 71-100% positive predictive value for hypovolemic hyponatremia responsive to saline 1, while **urine sodium >20-40 mmol/L with urine osmolality >300 mOsm/kg suggests SIADH 1

• Serum uric acid <4 mg/dL has a 73-100% positive predictive value for SIADH 1

Critical Safety Parameters for This Sodium Level

The severity of hyponatremia at 106 mmol/L places this patient at extraordinarily high risk for osmotic demyelination syndrome with any correction, even though she is currently asymptomatic. 1

• Maximum correction rate: 4-6 mmol/L per 24 hours for the first day, with an absolute maximum of 8 mmol/L in any 24-hour period 1

• Target sodium level is 125-130 mmol/L, NOT normalization to the normal range 1, 2

• Monitor serum sodium every 2-4 hours initially during active correction to ensure the rate does not exceed safe limits 1

Treatment Based on Volume Status

Hypovolemic Hyponatremia (Most Likely if Urine Sodium <30 mmol/L)

• Administer isotonic saline (0.9% NaCl) for volume repletion at an initial rate of 15-20 mL/kg/h for the first hour, then 4-14 mL/kg/h based on clinical response 1

• Discontinue any diuretics immediately if the patient is taking them 1

• Once euvolemia is achieved, switch to maintenance isotonic fluids at approximately 30 mL/kg/day 1

Euvolemic Hyponatremia (SIADH - if Urine Sodium >20-40 mmol/L, Urine Osmolality >300 mOsm/kg)

• Implement strict fluid restriction to 1 L/day (or 800 mL/day for refractory cases) as the cornerstone of treatment 1, 2

• If no response to fluid restriction after 24-48 hours, add oral sodium chloride 100 mEq (approximately 6 grams) three times daily 1

• For severe asymptomatic SIADH at this sodium level, consider urea 15-30 grams twice daily as an alternative to salt tablets, which may be better tolerated 2

• Vasopressin receptor antagonists (tolvaptan 15 mg once daily) may be considered for resistant cases, but require extremely careful monitoring to avoid overly rapid correction 1, 2

Hypervolemic Hyponatremia (Heart Failure, Cirrhosis - if Edema/Ascites Present)

• Implement fluid restriction to 1-1.5 L/day as first-line therapy 1

• Temporarily discontinue diuretics until sodium improves above 125 mmol/L 1

• For cirrhotic patients, consider albumin infusion (8 g per liter of ascites removed) alongside fluid restriction 1

• Avoid hypertonic saline in hypervolemic states unless life-threatening neurological symptoms develop, as it worsens fluid overload 1

Why Asymptomatic Status Does NOT Change the Cautious Approach

Despite the absence of symptoms, this sodium level requires the same cautious correction strategy:

• The brain has already adapted to chronic severe hyponatremia by reducing intracellular osmoles over 48-72 hours 1, 3

• Rapid correction in adapted brains causes osmotic demyelination syndrome (dysarthria, dysphagia, oculomotor dysfunction, quadriparesis) typically 2-7 days after overcorrection 1

• Even asymptomatic patients with sodium <120 mmol/L have increased mortality risk and require hospital admission for monitored correction 1

Monitoring Protocol

• Serum sodium every 2 hours for the first 6-8 hours, then every 4 hours for the first 24 hours 1

• Calculate sodium deficit using: Desired increase in Na (mEq/L) × (0.5 × ideal body weight in kg) 1

• If correction exceeds 6 mmol/L in the first 6 hours or approaches 8 mmol/L in 24 hours, immediately stop current fluids and switch to D5W (5% dextrose in water) or administer desmopressin to slow/reverse the rise 1

• Watch for signs of osmotic demyelination syndrome starting 2-7 days after correction begins 1

Common Pitfalls to Avoid

• Never aim for rapid normalization of sodium to 135-145 mmol/L; the goal is 125-130 mmol/L 1, 2

• Never use hypotonic fluids (0.45% saline, lactated Ringer's) in any hyponatremic patient, as they worsen the condition 1

• Never delay treatment while pursuing a complete diagnostic workup; begin correction based on volume status assessment while investigations proceed 4, 5

• Never apply fluid restriction if the patient has hypovolemic hyponatremia or cerebral salt wasting, as this worsens outcomes 1

• Never exceed 8 mmol/L correction in 24 hours regardless of how slowly you think you are correcting 1, 2