In a patient whose hyperglycaemic crisis has been treated and glucose is now normal but serum sodium remains 123 mmol/L, how should the persistent hyponatraemia be managed?

Management of Persistent Hyponatremia After Hyperglycemic Crisis Resolution

After correcting hyperglycemia and achieving normal glucose levels, persistent hyponatremia at 123 mmol/L requires immediate assessment of volume status and underlying etiology, followed by targeted treatment based on whether the patient is hypovolemic, euvolemic, or hypervolemic—with the critical principle that correction must never exceed 8 mmol/L in 24 hours to prevent osmotic demyelination syndrome. 1

Understanding the Clinical Context

During hyperglycemic crises, the measured serum sodium is artificially lowered by approximately 1.6 mmol/L for every 100 mg/dL of glucose above normal (pseudohyponatremia). 1, 2 Once glucose normalizes, the "true" sodium level becomes apparent. If sodium remains at 123 mmol/L after glucose correction, this represents genuine hyponatremia requiring specific management. 2

Immediate Assessment Steps

Volume Status Determination

Physical examination must assess for specific signs of volume status, though this alone has limited accuracy (sensitivity 41%, specificity 80%). 1

• Hypovolemic signs: orthostatic hypotension, dry mucous membranes, decreased skin turgor, flat neck veins, tachycardia 1
• Euvolemic signs: normal skin turgor, moist mucous membranes, no edema, no orthostatic changes 1
• Hypervolemic signs: peripheral edema, ascites, jugular venous distention, pulmonary congestion 1

Essential Laboratory Tests

• Urine sodium concentration: <30 mmol/L suggests hypovolemia (71-100% positive predictive value for saline responsiveness); >20-40 mmol/L with high urine osmolality suggests SIADH 1
• Urine osmolality: >100 mOsm/kg indicates impaired water excretion; >300-500 mOsm/kg supports SIADH 1, 3
• Serum osmolality: Should be low (<275 mOsm/kg) in true hypotonic hyponatremia 1, 3
• Thyroid function (TSH) and morning cortisol: To exclude hypothyroidism and adrenal insufficiency 1

Treatment Algorithm Based on Volume Status

If Hypovolemic (True Volume Depletion)

Administer isotonic saline (0.9% NaCl) for volume repletion 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
• Monitor urine sodium; values <30 mmol/L confirm appropriate response to volume repletion 1
• Target correction rate: 4-8 mmol/L per day, maximum 8 mmol/L in 24 hours 1, 4
• Check serum sodium every 4-6 hours during active correction 1, 4

Common pitfall: Using hypotonic fluids (0.45% saline, lactated Ringer's, D5W) will worsen hyponatremia and must be avoided. 1

If Euvolemic (Likely SIADH)

Fluid restriction to 1 L/day (or <800 mL/day for refractory cases) is the cornerstone of treatment. 1, 4

• If fluid restriction fails after 24-48 hours, add oral sodium chloride 100 mEq three times daily 1, 4
• Consider high-protein diet to augment solute intake 4
• For persistent cases, vasopressin receptor antagonists (tolvaptan 15 mg daily) may be considered 1
• Monitor serum sodium every 24 hours initially 1

Key principle: SIADH requires fluid restriction, NOT saline administration, which can paradoxically worsen hyponatremia. 1

If Hypervolemic (Heart Failure, Cirrhosis)

Implement fluid restriction to 1-1.5 L/day for sodium <125 mmol/L. 1, 4

• Temporarily discontinue diuretics if sodium <125 mmol/L 1
• For cirrhotic patients, consider albumin infusion (8 g per liter of ascites removed) alongside fluid restriction 1
• Avoid hypertonic saline unless life-threatening neurological symptoms develop, as it worsens fluid overload 1
• Target correction: 4-6 mmol/L per day in cirrhotic patients (maximum 8 mmol/L in 24 hours) 1, 4

Critical distinction: In cirrhosis, it is sodium restriction (not fluid restriction) that produces weight loss, as fluid follows sodium. 1

Special Considerations for Post-Hyperglycemic Crisis Patients

Insulin-Induced Fluid Shifts

During hyperglycemic crisis treatment, large volumes of fluid are administered, and insulin drives glucose (and water) intracellularly. 5, 6 This can create complex volume status:

• Assess total fluid balance during resuscitation: Patients receiving >6-7 L of dextrose-containing fluids may develop dilutional hyponatremia 6
• Evaluate for ongoing osmotic diuresis: If polyuria persists despite glucose normalization, consider cerebral salt wasting in neurosurgical contexts 1

Medication Review

Review all medications that can cause or worsen hyponatremia: 1

• SSRIs, carbamazepine, NSAIDs, opioids
• Chemotherapy agents (platinum-based, vinca alkaloids)
• Diuretics (thiazides more than loops)

Critical Safety Parameters

Correction Rate Limits

The single most important safety principle: NEVER exceed 8 mmol/L correction in any 24-hour period. 1, 4, 3, 7

• Standard-risk patients: 4-8 mmol/L per day 1
• High-risk patients (cirrhosis, alcoholism, malnutrition, prior encephalopathy): 4-6 mmol/L per day, absolute maximum 8 mmol/L in 24 hours 1, 4

Monitoring Protocol

• Serum sodium every 4-6 hours during active correction 1, 4
• Daily weights and strict intake-output monitoring 1
• Watch for osmotic demyelination syndrome signs (dysarthria, dysphagia, oculomotor dysfunction, quadriparesis) typically 2-7 days after rapid correction 1

Management of Overcorrection

If sodium rises >8 mmol/L in 24 hours: 1

• Immediately discontinue current fluids
• Switch to D5W (5% dextrose in water)
• Consider desmopressin to slow or reverse the rapid rise
• Target: bring total 24-hour correction back to ≤8 mmol/L from baseline

When to Use Hypertonic Saline (3% NaCl)

Reserve hypertonic saline ONLY for severe symptomatic hyponatremia with neurological manifestations (seizures, coma, altered mental status). 1, 4, 7

• Administer 100 mL boluses over 10 minutes, up to three times 1
• Target: 6 mmol/L correction over 6 hours or until symptoms resolve 1, 4
• Then switch to maintenance therapy based on volume status 1

This patient at 123 mmol/L without severe neurological symptoms does NOT require hypertonic saline. 1

Common Pitfalls to Avoid

• Ignoring mild hyponatremia (130-135 mmol/L) as clinically insignificant—even mild levels increase fall risk and mortality 1
• Correcting chronic hyponatremia faster than 8 mmol/L in 24 hours—this causes osmotic demyelination syndrome 1, 3, 7
• Using fluid restriction in hypovolemic patients—this worsens outcomes and delays recovery 1
• Administering normal saline to euvolemic (SIADH) patients—this can paradoxically worsen hyponatremia 1
• Failing to recognize and treat the underlying cause—hyponatremia will recur without addressing the primary etiology 1