Nephrology Book


Normoosmolar Hyponatremia

Aka: Normoosmolar Hyponatremia, Isoosmolar Hyponatremia, Isotonic Hyponatremia, Pseudohyponatremia
  1. See Also
    1. Hyponatremia
    2. Hyperosmolar Hyponatremia
    3. Hypoosmolar Hyponatremia
    4. Hyponatremia Management
    5. Sodium and Water Homeostasis
  2. Definition
    1. Hyponatremia with measured Serum Osmolality = 280-300
  3. Pathophysiology
    1. Water normally comprises 92-94% of serum
    2. Lipids or Proteins decrease water fraction
  4. Causes
    1. Pseudohyponatremia (Isotonic)
      1. Hyperlipidemia (Serum Triglycerides >1500 mg/dl)
      2. Hyperproteinemia (Serum Protein > 10 g/dl)
    2. Isotonic (Sodium-free) infusion
      1. Glucose
      2. Mannitol
      3. Glycine (used in some urologic procedures)
      4. Post-Transurethral prostatic resection syndrome
        1. Large volume intraoperative hypotonic irrigation
        2. Neurologic and cardiopulmonary signs
  5. Labs
    1. Pseudohyponatremia is not an issue when Serum Sodium is measured by Sodium electrode
      1. In this case, measured Sodium is the true Sodium concentration
      2. Many labs in U.S. (as of 2015) use Sodium electrode to measure Serum Sodium
  6. Management
    1. Pseudohyponatremia
      1. In Pseudohyponatremia, Sodium does not need to be managed specifically
      2. Evaluate and treat underlying cause
        1. Hyperlipidemia
        2. Hyperproteinemia (e.g. Multiple Myeloma - consider SPEP, UPEP)
    2. Isotonic Infusion
      1. Reflects true Hyponatremia and requires correction
  7. 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]

Pseudohyponatremia (C0342582)

Concepts Finding (T033)
SnomedCT 237843009
English Hyponat+normal/incr serum osmo, pseudohyponatremia, pseudohyponatremia (diagnosis), Hyponatraemia with normal or increased serum osmolality, Hyponatremia with normal or increased serum osmolality, Pseudohyponatraemia, Pseudohyponatremia, Pseudohyponatremia (disorder)
Czech Pseudohyponatrémie, Pseudo-hyponatrémie
Dutch pseudohyponatriëmie
French Pseudo-hyponatrémie
German Pseudohyponatraemie
Hungarian Pseudo-hyponatremia, Pseudo-hyponatraemia
Italian Pseudoiponatremia
Spanish Seudohiponatremia, seudohiponatremia (trastorno), seudohiponatremia
Japanese ギセイテイナトリウムケツショウ, ギセイテイナトリウムケッショウ, 偽性低ナトリウム血症
Portuguese Pseudo-hiponatremia
Derived from the NIH UMLS (Unified Medical Language System)

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