A simple single injection method for determination of the extracellular fluid volume

Abstract

From measurements in eighty-six adults it is shown how the distribution volume of [⁵¹Cr]EDTA, as an estimate of the extracellular fluid volume (ECV), can be determined accurately using a simplified single injection method. The method only needs drawing of a few blood samples 3–5 h after a quantitative i.v. injection of [⁵¹Cr]EDTA and measurement of the subject's body weight. The glomerular filtration rate (GFR) can be calculated from the same few data, and with it, the ratio ECV/GFR or the reverse ratio GFR/ECV. These easily determined ratios might be relevant measurements of the kidney's main function: regulation of composition and size of the extracellular fluids, since they indicate how often 'that which is to be regulated' (i.e. the extracellular fluids) comes into contact with ‘the regulator’ (i.e. the kidney).

Key Words:

• distribution volume
• glomerular filtration rate
• plasma clearance
• radioisotopes
• tracer kinetics