title: Measuring the size of the extracellular fluid space using bromide, iohexol, and sodium dilution.
abstract: There is a need to find methods to assess the size of the extracellular fluid (ECF) volume without involving radioactive tracers. For this purpose, we applied 3 methods for measuring the ECF volume in 10 male volunteers (mean age, 34 yr). Steady-state plasma bromide concentration (control) was compared to the results of kinetic analysis of plasma iohexol and to kinetic analysis of the dilution of serum sodium after IV infusion of 1 L of isotonic mannitol. The volume of distribution of these tracers was used to indicate the ECF volume. The results disclosed statistically significant correlations between the results of all 3 methods, although the average sodium dilution showed 0.7 L lower values than iohexol and 1.4 L lower than bromide. All three methods correlated significantly with body weight. The percentage of the body weight indicated by the methods was 18.3% (3.1%) for sodium, 19.6% (1.0%) for iohexol, and 20.5% (1.1%) for bromide. We conclude that sodium dilution may be performed at bedside but iohexol and bromide showed less intersubject variability. Iohexol simultaneously measures the glomerular filtration rate and should be a viable clinical option if the hospital performs routine assessments of kidney function using this tracer.
authors.affiliation: *Department of Anesthesiology, University Hospital, Linköping, Sweden; †Department of Anesthesiology, Karolinska Institute, Stockholm, Sweden.
authors.forename: Joachim H
authors.initials: JH
authors.lastname: Zdolsek
authors.forename: Björn
authors.initials: B
authors.lastname: Lisander
authors.forename: Robert G
authors.initials: RG
authors.lastname: Hahn
mesh_terms: D000328:Adult; D001965:Bromides / Q000493:pharmacokinetics; D045604:Extracellular Fluid; D005919:Glomerular Filtration Rate; D006801:Humans; D007201:Indicator Dilution Techniques; D007472:Iohexol; D008297:Male; D008353:Mannitol / Q000493:pharmacokinetics; D008875:Middle Aged; D012964:Sodium
chemical_list: D001965:Bromides; D008353:Mannitol; D007472:Iohexol; D012964:Sodium