Perioperative Management of Hyponatremia

Risk Assessment and Preoperative Optimization

The American College of Surgeons recommends that elective surgery be postponed in patients with hyponatremia until the sodium level is corrected to at least 135 mmol/L, as hyponatremia is independently associated with increased perioperative morbidity and mortality 1
Severe hyponatremia (<130 mmol/L) carries a 60-fold increase in hospital mortality (11.2% versus 0.19% in normonatremic patients), and surgery must be postponed at this level 1
Even asymptomatic patients with severe hyponatremia require treatment before any elective procedure 1
The risk-benefit calculation favors postponement for truly elective procedures in patients with moderate hyponatremia (130-134 mmol/L) 1
This range is associated with significantly increased perioperative complications, including falls (21% versus 5% in normonatremic patients) 1

Never exceed 8 mmol/L correction in 24 hours to prevent osmotic demyelination syndrome 1, 2, 3
High-risk patients (advanced liver disease, alcoholism, malnutrition, prior encephalopathy) require even slower correction at 4-6 mmol/L per day 2, 3
Monitor sodium levels every 4-6 hours during active correction 2

Obtain serum and urine osmolality, urine sodium, and assess volume status to determine the etiology of hyponatremia 2, 3
Measure uric acid (levels <4 mg/dL suggest SIADH with 73-100% positive predictive value) 2
Check thyroid function and morning cortisol to exclude endocrine causes 2

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 in hypovolemic hyponatremia 2
Implement fluid restriction to 1 L/day as first-line treatment in euvolemic hyponatremia (SIADH) 2, 3
Consider vasopressin receptor antagonists (tolvaptan 15 mg daily) for resistant cases of euvolemic hyponatremia (SIADH) 2

Use isotonic fluids (0.9% NaCl or balanced crystalloids) exclusively and avoid hypotonic solutions 2
Minimize total fluid volume to reduce the substrate for electrolyte-free water generation 2
Monitor urine output and electrolytes closely 2
Check sodium levels every 4-6 hours for the first 24 hours postoperatively 2
Continue daily sodium monitoring for at least 7-10 days (14 days for neurosurgical procedures) 2