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Osmolality measures solute concentration in body fluids. It's critical for diagnosing hyponatremia, hypernatremia, and fluid disorders.
公式
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
ステップバイステップガイド
- 1Calculate: Osm = 2[Na] + (Glu/18) + (BUN/2.8)
- 2Normal: 280-310 mOsm/kg
- 3Compare measured to calculated osmolality
解いた例
入力
Na 128, glucose 200, BUN 28
結果
Osm ≈ 318 (high), measured lower suggests hyponatremia
Pseudohyponatremia likely
避けるべきよくある間違い
- ✕Neglecting glucose and BUN contributions in hyperglycemia/uremia
- ✕Confusing osmolality with osmolarity (different in concentrated solutions)
よくある質問
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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