Hirota, Ishihara et al developed an equation for estimating the initial distribution volume of glucose (IDVG). This is a measure of the central extracellular fluid volume and an indirect measure of cardiac preload. The authors are from the University of Hirosaki in Japan.
Method:
(1) 10 mL of a 50% glucose solution (5 grams) is injected through a central line.
(2) Blood samples are taken from a radial artery catheter at baseline before injection and then 3, 4 5 and 7 minutes after injection.
(3) Plasma samples were found preferable to whole blood.
change in glucose in mg/dL =
= (glucose at 3 minutes after injection in mg/dL) - (glucose at baseline in mg/dL)
X =
= (-0.03 * (change in glucose))
approximate initial distribution volume of glucose in liters =
= (24.4 * EXP(X)) + 2.7
Limitations:
• The values for glucose need to be accurate. A 1 mg/dL difference in a value can affect the results.
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