II. Definition

  1. Hyponatremia with Measured Serum Osmolality >300 mOsm

III. Pathophysiology

  1. Effective osmoles (e.g. excessive Glucose) create a hypertonic, hyperosmolar extracellular fluid
  2. Results in a transcellular shift of water out of cells into extracellular fluid
  3. Results in dilution of Sodium with Hyponatremia

IV. Causes

  1. Hypertonic infusion
    1. Glucose
    2. Mannitol
    3. Glycine
    4. Sorbitol
    5. Radiocontrast Material
  2. Hyperglycemia
    1. Associated Conditions
      1. Diabetic Ketoacidosis
      2. Hyperosmolar Hyperglycemic Nonketotic Coma
    2. Calculation
      1. Sodium falls 1.6 meq/L per 100 mg/dl Glucose rise above 100 mg/dl
      2. Sodium falls 2.4meq/L per 100 mg/dl Glucose rise above 400 mg/dl

V. References

  1. Kone in Tisher (1993) Nephrology, p. 87-100
  2. Levinsky in Wilson (1991) Harrison's IM, p. 281-84
  3. Rose (1989) Acid-Base and Electrolytes, p. 601-38
  4. Braun (2015) Am Fam Physician 91(5): 299-307 [PubMed]

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