Nephrology Book

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HypernatremiaAka: High serum sodium

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  1. Definition
    1. Serum Sodium exceeds 145 meq/liter
  2. Epidemiology
    1. Incidence: 1% of hospitalized elderly patients
  3. Pathophysiology
    1. Free water deficient state
      1. Total Body Water deficit > Total Body Sodium Deficit
      2. Excess water loss or excess sodium retention
    2. Lacks normal physiologic response to free water loss
      1. Inability to concentrate urine or inadequate ADH secretion
      2. Lack of thirst response or inadequate access to free water
  4. Signs and Symptoms
    1. Lethargy
    2. Restlessness
    3. Hyperreflexia
    4. Spasticity
    5. Seizure
  5. Causes
    1. See specific types below
    2. Hypernatremia with polyuria in hospitalized patients is common
      1. Results from parenteral or enteral feeds and
      2. Increased free water lost or inadequate free water intake
  6. Types: Based on Volume Status
    1. Hypervolemic Hypernatremia
      1. Hypernatremia with Increased Total Body Sodium
    2. Isovolemic Hypernatremia
      1. Hypernatremia with Normal Total Body Sodium
    3. Hypovolemic Hypernatremia
      1. Hypernatremia with Decreased Total Body Sodium
  7. Labs (Dependent on Hypernatremia subtype as above)
    1. Serum labs
      1. Serum Glucose
      2. Serum Calcium
      3. Serum Creatinine and Blood Urea Nitrogen
    2. Urine labs
      1. Urine volume
      2. Urine Sodium
      3. Urine Potassium
      4. Urine Chloride
      5. Urine Calcium
    3. Calculations based on above
      1. Serum osmalality
      2. Serum to urine electrolyte ratio
        1. Urine electrolytes: Urine Sodium + Urine Potassium
        2. Serum electrolytes: Serum Sodium + Serum Potassium
        3. Interpretation (question whether kidney is excreting or retaining electrolyte-free water)
          1. Concentrated urine: Urine electrolytes exceed serum electrolytes
          2. Dilute urine: Serum electrolytes exceed urine electrolytes
  8. Management
    1. See specific Hypernatremia types based on fluid status
  9. Complications of cerebral dehydration
    1. Cerebral hemorrhage
      1. Subarachnoid Hemorrhage
      2. Subcortical hemorrhage
    2. Venous sinus thrombosis
  10. Prognosis: Mortality
    1. Children
      1. Acute Hypernatremia: 43%
      2. Chronic Hypernatremia: 7-29%
    2. Adults
      1. Acute Hypernatremia: 60%

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