Osmolal or Osmolar Gap: Difference between revisions

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==Definitions==
==Definitions==
Osmolarity = the total number of particles in solution per liter
*Osmolarity = the total number of particles in solution per liter
 
*Osmolality = the number of particles per kilogram of solvent
Osmolality = the number of particles per kilogram of solvent
 
==Background==
Serum osmolality should be measured by the freezing-point depression method rather than by the vapor pressure method, since the latter technique will underestimate the concentrations of volatile alcohols (methanol, ethylene glycol, and isopropanol).


==Calculations==
==Calculations==
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===Osmolal Gap===
===Osmolal Gap===
Osmolal Gap = measured osm - calculated osm
*Normal = +/- 14-10 mOsm/L


Osmolal Gap = measured osm - calculated osm
==Differential Diagnosis==
*[[EtOH]]
*[[Ethylene glycol]]
*[[Methanol]]
*[[Isopropyl alcohol toxicity]]
*[[Diethylene glycol]]
*[[Propylene glycol]]
*[[Mannitol]]
*Glycerol
*Smaller gaps possible in:
**[[ketonemia|Ketoacidosis]]
**[[Lactic acidosis]]
**[[Chronic kidney disease]]
 
==See Also==
*[[Anion Gap and Osmolar Gap (High)]]
*[[Anion Gap (High)]]
*[[Toxidromes]]


(Normal = (-)14-10 mOsm/L)
==External Links==
*[http://www.mdcalc.com/serum-osmolality-osmolarity/ MDCalc - Serum Osmolality/Osmolarity]
*[http://www.mdcalc.com/anion-gap/ MDCalc - Anion Gap]


==DDX==
==References==
===Increased)===
<references/>
#Alcohols
##methanol
##ethylene glycol
##isopropanol
#Sugar
##glycerol
##manitol
#Ketones
##acetone


[[Category:FEN]]
[[Category:FEN]]
[[Category:Tox]]
[[Category:Toxicology]]

Latest revision as of 16:29, 29 September 2019

Definitions

  • Osmolarity = the total number of particles in solution per liter
  • Osmolality = the number of particles per kilogram of solvent

Calculations

Calculated Osm

Calculated Osm = 2 x Na + (glu/18) + (BUN/2.8) + (ethanol/4.6) + (methanol/2.6) + (ethylene glycol/5) + (acetone/5.5) + (isopropanol/5.9)

  • Normal = 275-295

Osmolal Gap

Osmolal Gap = measured osm - calculated osm

  • Normal = +/- 14-10 mOsm/L

Differential Diagnosis

See Also

External Links

References