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| ==Background==
| | #REDIRECT [[Osmolal or Osmolar Gap]] |
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| ===Osmolar Gap===
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| *Primary determinants are sodium, glucose, BUN, chloride
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| *Osmolal gap
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| **When measured minus calculated > 10
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| **Suggests unmeasured, low molecular weight solutes
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| ====Values====
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| *Calculated osmolarity = '''2Na + Gluc/18 + BUN/2.8'''
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| **Sodium multiplied by two to account for physiologic anions (chloride and bicarbonate)
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| **Na in mEq/L, Glucose in mg/dL, BUN in mg/dL
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| **Normal 280-295 mosmol/kg
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| ====DDx====
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| *EtOH
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| *[[Ethylene glycol]]
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| *[[Methanol]]
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| *[[Isopropyl alcohol toxicity]]
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| *[[Diethylene glycol]]
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| *[[Propylene glycol]]
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| *[[Mannitol]]
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| *Glycerol
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| *Smaller gaps possible in:
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| **Ketoacidosis
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| **[[Lactic acidosis]]
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| **[[Chronic kidney disease]]
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| ==Sources==
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| *Emmett M et al. Serum osmolal gap. UpToDate. Aug 25, 2014. http://www.uptodate.com/contents/serum-osmolal-gap.
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| [[Category:FEN]]
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