Prognostic value of serum osmolality gap in patients with multiple organ failure treated with hemopurification

Serum osmolality gap (OG), the difference between measured and predicted serum osmolality, has been shown to be an excellent parameter to express the amount of conventionally unmeasurable middle-molecular-weight substances. OG was determined on 29 patients with multiple organ failure (MOF) treated with or without hemopurification. OG significantly increased in proportion to the increase in the number of failed organs and correlated well with APACHE II score. Nonsurvivors showed persistently high OG. OG decreased with plasma exchange and hemoadsorption, but not with hemodialysis, indicating that pathogenic factors can be removed effectively with plasma exchange and hemoadsorption. The patients with OG greater than 20 mOsm/kg-H2O had very little possibility of survival. These results indicate that OG is an easily determinable, effective parameter to evaluate the severity of the patients' condition, efficacy of hemopurification in removing pathogenic middle-molecular-weight substances, and the prognosis of the patient in the treatment of MOF.