Hypernatremia

Hypernatremia

David Ray Velez, MD

Definition: Sodium (Na) > 145 mEq/L

  • Acute Hypernatremia: < 48 Hours
  • Chronic Hypernatremia: > 48 Hours or Unknown

Severity

  • Mild: Na > 145 mEq/L
  • Moderate: Na ≥ 150 mEq/L
  • Severe: Na ≥ 170 mEq/L
  • *Definitions Vary and Multiple Different Levels Have Been Used in Classification

Classification

  • Hypovolemic Hypernatremia: Total Body Water Decreases More Than a Decrease in Total Body Sodium
  • Euvolemic Hypernatremia: Total Body Water Decreases with a Stable Total Body Sodium
  • Hypervolemic Hypernatremia: Total Body Water Increases Less Than an Increase in Total Body Sodium

Causes

  • Excessive Fluid Loss
    • Vomiting
    • Nasogastric/Orogastric Tube Drainage
    • High Urine Output
      • Osmotic Diuresis
      • Diabetes Insipidus (DI)
    • Sweating
  • Poor Fluid Intake
  • Exogenous Administration of Sodium (Salt Poisoning or Hypertonic IV Solutions)

Presentation

  • Lethargy
  • Weakness
  • Irritable
  • Restless
  • Seizure
  • Coma

Free Water Deficit

  • Free Water Deficit = Total Body Water x (Na – 140)/140
    • Also Equivalent to = Total Body Water x ((Na/140) – 1)
  • Total Body Water:
    • Total Body Water (Males) = Weight (Kg) x 60%
    • Total Body Water (Females) = Weight (Kg) x 50%

Treatment

  • Acute Hypernatremia (< 48 Hours): Replace Entire Free Water Deficit in 24 Hours
    • Fluid Choice: 5% Dextrose in Water (D5W) or Enteral Free Water
  • Chronic Hypernatremia (> 48 Hours): Replace Half the Free Water Deficit in 24 Hours
    • Fluid Choice: 0.45% Sodium Chloride (Half-NS) or Enteral Free Water
    • Goal: Decrease Sodium by 8-10 mEq/L/Day
      • 5 mEq/L/Hour
    • Avoid Correction Over 12 mEq/L Per Day
      • Risk for Cerebral Edema with Over-Correction
    • Management of Diabetes Insipidus: *See Diabetes Insipidus (DI)