How to replenish sodium in the Emergency Department (ED)?

Management of Hyponatremia in the Emergency Department

For symptomatic hyponatremia in the ED, administer 3% hypertonic saline with a goal of correcting sodium by 6 mmol/L in the first 6 hours or until severe symptoms resolve, not exceeding 8 mmol/L in 24 hours. 1

Assessment of Hyponatremia

First, determine the severity of symptoms:

• Severe symptoms: Mental status changes, seizures, coma
• Mild symptoms: Nausea, vomiting, headache, weakness
• Asymptomatic: No clinical manifestations

Then, assess volume status:

• Hypovolemic: Dry mucous membranes, decreased skin turgor, orthostatic hypotension
• Euvolemic: Normal clinical examination
• Hypervolemic: Edema, ascites, elevated jugular venous pressure

Treatment Algorithm

Severe Symptomatic Hyponatremia (Emergency)

1. Administer 3% hypertonic saline:

   • Give as bolus infusion: 100 mL of 3% saline over 10-20 minutes
   • Can repeat up to 2 more times if symptoms persist
   • Target increase: 4-6 mmol/L within first 1-2 hours 2

2. Monitor sodium levels:

   • Check serum sodium every 2 hours initially
   • Adjust treatment based on response

3. Prevent overcorrection:

   • Limit correction to 6-8 mmol/L in first 24 hours
   • Be prepared to use dextrose/dDAVP if correction is too rapid, especially after third bolus 3

Mild to Moderate Symptomatic Hyponatremia

1. 3% hypertonic saline:

   • Lower dose continuous infusion (20 mL/hr) or smaller boluses
   • Target increase: 0.5 mmol/L/hour 4

2. Monitor sodium levels:

   • Check serum sodium every 4 hours
   • Adjust treatment based on response

Hypovolemic Hyponatremia

1. Fluid resuscitation:

   • Isotonic saline (0.9% NaCl) at 15-20 mL/kg/hr initially 5
   • Once renal function is assured, add potassium (20-30 mEq/L; 2/3 KCl and 1/3 KPO₄) 5

2. Monitor diuresis:

   • Increased diuresis correlates with risk of overcorrection 6
   • Adjust fluid therapy accordingly

Euvolemic or Hypervolemic Hyponatremia

1. Fluid restriction (<1 L/day) 1
2. Consider vasopressin receptor antagonists as second-line treatment for appropriate cases

Cautions and Pitfalls

• Avoid overcorrection: Correction >8-10 mmol/L/24 hours increases risk of osmotic demyelination syndrome, especially in:

  • Chronic hyponatremia (>48 hours)
  • Malnourished patients
  • Alcoholics
  • Patients with liver disease 1

• Monitor for rebound hyponatremia: Particularly in SIADH after initial correction

• Avoid fluid restriction in cerebral salt wasting: Can worsen cerebral perfusion 1

• Misinterpretation of symptoms: Hypovolemic symptoms can be misinterpreted as severe hyponatremia symptoms 6

Special Considerations

• Potassium supplementation: Include when replacing fluids once renal function is assured

• Pediatric patients: More conservative approach with fluid resuscitation (10-20 mL/kg/hr initially, not exceeding 50 mL/kg in first 4 hours) 5

• Underlying causes: Identify and treat the underlying cause while managing the acute electrolyte disturbance

By following this structured approach to sodium repletion in the ED, you can effectively manage hyponatremia while minimizing the risk of complications from both the condition itself and its treatment.