Hyponatremia

 

 

 

Considerations

 

  • Acute vs. chronic hyponatremia 

  • Central pontine myelinolysis from rapid overcorrection

  • Physiologic manifestations (severe = neurologic symptoms or < 120 mEq/L):

    • CNS: ↓ LOC, seizures, cerebral edema, central pontine myelinolysis 

    • Hyper- or hypovolemia

    • Respiratory arrest

    • ↓ MAC 

  • Etiology:

    • Hypervolemia:

      • Congestive heart failure 

      • Hypoalbuminemia (cirrhosis, nephrotic syndrome)

      • Renal failure

      • TURP syndrome

    • Euvolemia:

      • SIADH (stress, pain, post neurosurgery)

      • Psychogenic

    • Hypovolemia: 

      • Cerebral salt wasting

      • Hemorrhage

      • Addison's disease 

      • Peritonitis

      • Edema from burns

      • Diarrhea

      • Diuretics

 

 

Management

 

  • Correct severe hyponatremia before surgery 

  • Restore volume deficit

    • Normal saline 20mL/kg IV bolus prn

  • Restore plasma sodium concentration

    • Acute: 

      • Generally restrict free water (500mL-1L/day) +/- diuretic 

      • Severe hyponatremia (< 120mEq/L or presence of neurologic symptoms)

        • Hypertonic saline 3% 1-2 ml/kg/hr until Na>125

        • Loop diuretics

        • Sodium bicarbonate (1 mEq/ml) to terminate seizures: 0.5-1mL/kg boluses prn

    • Chronic: avoid rapid overcorrection (0.5-1 mEq/hr, < 8 in mEq in 24hrs)

  • SIADH: treat underlying cause & fluid restriction

  • Identify & treat mineralocorticoid deficiency