Hyponatremia (Na⁺ 127 mEq/L) and Heart Valve Surgery: Risk Assessment and Correction Strategy

Serum sodium of 127 mEq/L represents moderate hyponatremia and significantly increases perioperative risk for heart valve surgery.

Pathophysiologic Risks

• Cardiac electrophysiology: Hyponatremia prolongs action potential duration, predisposes to arrhythmias (AF, VT/VF), especially with cardiopulmonary bypass (CPB) electrolyte shifts.
• Neurologic: Cerebral edema risk with rapid correction; seizures, osmotic demyelination if overcorrected (>8–10 mEq/L/24h).
• Hemodynamic: SIADH vs. hypovolemic vs. hypervolemic etiology dictates fluid management; CPB exacerbates capillary leak.
• Coagulopathy: Hyponatremia impairs platelet function and fibrinolysis.

Preoperative Correction Protocol

1. Identify etiology: Medication review (diuretics, SSRIs), volume status, endocrine (cortisol, thyroid), renal/hepatic/cardiac function.
2. Target: Na⁺ 135–145 mEq/L before surgery.
3. Hypovolemic: Isotonic saline (0.9% NaCl) resuscitation.
4. Euolemic (SIADH): Fluid restriction (800–1000 mL/day), salt tablets, consider vaptans (tolvaptan) if chronic/symptomatic.
5. Hypervolemic (HF, cirrhosis): Diuresis + fluid/salt restriction; avoid rapid shifts.
6. Correction rate: ≤6–8 mEq/L/24h; ≤18 mEq/L/48h. Frequent monitoring (q2–4h initially).

Emergency Surgery Exception

Life-threatening conditions (acute severe aortic stenosis with pulmonary edema, endocarditis with septic shock, prosthetic valve thrombosis) may necessitate proceeding despite hyponatremia. In such cases:

• Initiate correction concurrently.
• Intraoperative blood gas/electrolyte monitoring q15–30 min.
• Priming solution adjustment (mannitol, hypertonic saline).
• Post-op ICU management with strict Na⁺ targets.

Multidisciplinary coordination (cardiac surgery, anesthesia, nephrology, critical care) is essential.