Anesthesia Considerations 

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