Comparison of the calculated and measured osmolality in intracranial bleeding and head injury patients

J Emerg Med. 2009 Feb;36(2):217-9. doi: 10.1016/j.jemermed.2007.11.075. Epub 2008 May 16.


Not all clinical laboratories have an osmometer, and calculations for osmolality are a frequently used method for determining osmolality. The purpose of this study was to evaluate the performance of four formulas for the estimation of osmolality, with cryoscopic measurement as the reference standard in intracranial hemorrhage (ICH) and head injury (HI) patients who were not treated with mannitol. Forty HI and 31 ICH patients treated in the Neurosurgery Department were included in the study. Every 6 h over a period of 24 h, serum samples were collected from patients and osmolality was measured. In conclusion, our study shows that only formulas F1 [Osmolality = 1.86(Na) + 1.86(K) + Glucose + Urea] and F4 [Osmolality = 1.86(Na) + Glucose + Urea + Ethanol + 9] can be used to evaluate osmolality in ICH patients who were not treated with mannitol. In HI patients, none of the formulas should be used to calculate osmolality.

Publication types

  • Comparative Study

MeSH terms

  • Algorithms*
  • Blood Chemical Analysis / methods
  • Electrolytes / blood*
  • Head Injuries, Closed / blood*
  • Humans
  • Intracranial Hemorrhages / blood*
  • Osmolar Concentration
  • Transition Temperature
  • Water-Electrolyte Balance


  • Electrolytes