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Як розрахувати Osmolality

Що таке Osmolality?

Osmolality measures solute concentration in body fluids. It's critical for diagnosing hyponatremia, hypernatremia, and fluid disorders.

Формула

Calculate: Osm = 2[Na] + (Glu/18) + (BUN/2.8)
Na
Na value — Variable used in the calculation
BUN
BUN value — Variable used in the calculation

Покрокова інструкція

  1. 1Calculate: Osm = 2[Na] + (Glu/18) + (BUN/2.8)
  2. 2Normal: 280-310 mOsm/kg
  3. 3Compare measured to calculated osmolality

Розв'язані приклади

Введення
Na 128, glucose 200, BUN 28
Результат
Osm ≈ 318 (high), measured lower suggests hyponatremia
Pseudohyponatremia likely

Поширені помилки

  • Neglecting glucose and BUN contributions in hyperglycemia/uremia
  • Confusing osmolality with osmolarity (different in concentrated solutions)

Часті запитання

What's the osmolal gap?

Difference between measured and calculated osmolality. Large gap suggests unmeasured osmoles (ethanol, methanol, etc.).

How does osmolality relate to sodium?

Sodium is the main determinant of osmolality; hyponatremia usually means hypoosmolality and vice versa.

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