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Kako izračunati Osmolality

Što je Osmolality?

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

Formula

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

Vodič korak po korak

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

Worked Examples

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

Common Mistakes to Avoid

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

Frequently Asked Questions

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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