Day 3 - Hyponatremia

Approach to Asymptomatic Hypo-osmolar Hyponatremia:

Goal is to correct 8mEq/24h

  1. Determine severity, symptoms and acuity

  2. Assess Volume Status

    • Hypovolemic? (UNa < 20)

      • Start IVF 0.9% NaCl at 50-100ml/h

    • Hypervolemic? (UNa < 20)

      • Trial Diuresis

    • Euvolemic?

      • SiADH - most common cause (UNa > 40, Urine Osmol > 100)

        • Fluid restriction to < 1.5L/24 hours

        • Consider Salt Tabs for refractory SiADH

  3. Insert Foley to monitor for urine output

    • Patients with LOW solute (ie: beer potomania, tea and toasters) may have significant diuresis when IVF started. Diuresis can cause rapid overcorrection. DDAVP/D5W infusion should be started immediately if urine output increases by 50% or if U/O is >250ml/h.

  4. Check Na+ q4h - at minimum. If unavailable, consider nephrology consult or rapid access consult

  5. Overcorrection?

    • DDAVP 2-4mcg IV x 1, r/a q4h

    • If DDAVP unavailable, can use D5W infusion as free water

Assess Severity

  1. Mild - Serum Na 130-135

  2. Moderate - Serum Na 120 - 130

  3. Severe -Serum Na < 120

Acute or Chronic?

  • Acute < 48 hours

  • Chronic > 48 hours

*Chronic hyponatremia has increased risk of overcorrection and ODS

Important Lab Values:

  • Serum electrolytes, Serum osmolality, Urine Electrolytes, Urine Osmolality

Is it Pseudohyponatremia?

  • In patients with normal or high serum osmolality, consider pseudohyponatremia

    • ie: Paraproteinemia, severe hyperglycaemia, post-TURP syndrome

Symptomatic or Asymptomatic?

  • Altered LOC

  • General Weakness

  • Seizures (generally not seen unless Na < 125)

Hyponatremic Emergencies:

  • Includes seizures, evidence of elevated ICP

  • Start 3% NaCl

    • ~150 ml bolus in first hour, then 30ml/h x 3 hours

    • Goal is to increase by 5mmol in first hour

  • Recommend Nephrology Consult

The Intern at Work -