A new method for plasma volume measurements with unlabeled dextran-70 instead of 125I-labeled albumin as an indicator

doi:10.1016/S0009-8981(98)00080-1

Clinica Chimica Acta

Volume 275, Issue 1, 6 July 1998, Pages 71-80

https://doi.org/10.1016/S0009-8981(98)00080-1 Get rights and content

Abstract

A method has been developed to determine plasma volume with dextran-70 without the use of a fluorescent label. The results obtained are compared to those found using the ¹²⁵I-labeled albumin method, which is taken as the gold standard. The CV of the method is about 5%, compared to 3% with the gold standard. It is shown to be of use for the determination of an increase in plasma volume during pregnancy.

Introduction

Widely accepted indicators to quantify plasma volume (PV) by indicator dilution are ¹²⁵1-labeled albumin [3] and the dyes Evans blue [1] and indocyanine green [2]. A major disadvantage of the latter two dye indicators is their rapid escape from the intravascular space, giving rise to overestimation of the PV [5]. Therefore, ¹²⁵I-labeled albumin appears to be a more reliable indicator, but requires the administration of radioactivity to an individual, as well as access to a specialized facility for administration and quantification of radiation. Therefore, high-molecular weight dextran may represent an attractive alternative to measure PV [6] as it seems to combine the advantages of ¹²⁵I-labeled albumin (a relatively long half-life and a distribution space that is probably closer to that of PV) with those of the dyes (nonradioactivity). Instead of using radiolabels, dextrans used for this purpose are usually coupled to fluorescent compounds [7].

In the present study, we tested the hypothesis that dextran-70 represents a safe and reliable indicator to quantify PV (changes) in conditions such as pregnancy, when PV increases by more than 1 L in a relatively short period [4]. For application in patients, health risks should be kept to a minimum. Therefore, we tested pure dextran-70 without any label as an indicator to measure PV in 20 nonpregnant women using ¹²⁵I-labeled albumin as a reference. Dextran-70 was quantitated by enzymatic determination of glucose, the only degradation product of dextran-70 after hydrolysis. The sensitivity and specificity of this measurement technique is high, thus limiting the amount of indicator that has to be injected and, with it, the risk of immune reactions [8].

Section snippets

Subjects

This study was performed in 20 parous women with a regular menstrual cycle. Their ages ranged from 23 to 38 years. All subjects gave informed consent after receiving all relevant information with respect to potential risks of intravenous administration of dextran-70 and ¹²⁵I-labeled albumin. The time of measurement was chosen to be early in the follicular phase and always at the same time of day.

¹²⁵I-labeled albumin: measurement of the distribution space

A known quantity of ¹²⁵I-labeled albumin containing 5 μCi of ¹²⁵I was transferred into a volumetric

Removal of free glucose

The concentration of dextran was measured by determining the glucose concentration after acid hydrolysis of the dextran as follows: Four serum samples were obtained from one patient: S₀, S₁₀, S₂₀, S₃₀. The S₀ sample (called the blank sample subsequently) did not contain dextran but did contain glucose, of course. After hydrolysis, glucose was measured. The glucose derived from dextran equals glucose sample (S₁₀, S₂₀, S₃₀) minus glucose blank (S₀). A SD will result from both determinations. The

Effect of yeast addition on concentration

Because it is possible that the addition of yeast will influence the measurement of dextran, two series of dextran solutions in water were prepared with concentrations of dextran-70 corresponding to 1.6 to 24.8 mmol/L glucose. To each sample of one series, 200 mg of yeast were added to 1.5 mL of dextran-70. All of the samples were then incubated for 1 h at 37°C. Then, the amount of glucose formed from dextran after hydrolysis was determined for both series as described above. The results are

Discussion

In this study, we evaluated how dextran-70 would compare with ¹²⁵I-labeled albumin as an indicator for the measurement of PV. Dextran-70 is an attractive compound to be used as an indicator for the measurement of PV, primarily because of its simple biochemical configuration: a polymer of glucose with a molecular weight of 70,000 Da. The half-life after intravenous injection in a human is approx. 12 h. The procedure for measuring PV with dextran-70 is similar to that with the gold standard, ¹²⁵

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The volume of distribution of high-molecular weight Dextran and its relation to plasma volume in man
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M.Y. Anthony et al.
Measurement of plasma volume in neonates
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A Method for Assessment of Blood Volume Parameters in Pregnant Sheep using Fluorescein-labelled Dextran
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PV and BV were estimated in yellowfin tuna using a commercially available fluorescein-labelled dextran, and did not differ significantly from BV measured using radiolabelled red cells [8]. However, PV estimated in pregnant women using a 70 kDa dextran was approximately 50 mL greater than results obtained using 125I-labelled albumin [9]. We wished to assess the blood volume parameters of pregnant sheep in response to changes in nutrition before and during pregnancy.
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A new method for plasma volume measurements with unlabeled dextran-70 instead of 125I-labeled albumin as an indicator

Abstract

Introduction

Section snippets

Subjects

125I-labeled albumin: measurement of the distribution space

Removal of free glucose

Effect of yeast addition on concentration

Discussion

Microvasc Res

The volume of distribution of high-molecular weight Dextran and its relation to plasma volume in man

J Lab Clin Med

Measurement of plasma volume in neonates

Arch Dis Child

Recommended methods for red cell and plasma volume

J Nucl Med

A new method for plasma volume measurements with unlabeled dextran-70 instead of ¹²⁵I-labeled albumin as an indicator

¹²⁵I-labeled albumin: measurement of the distribution space