Plasma Volume Measurement Using Tagged Macromolecules
Lead Inventors: Bashir ZikriaProblem or Unmet Need:In sick patients inflammatory signals result in "capillary leak" allowing albumin to leak out of the capillaries into the interstitial space. Historically plasma volume has been measured with iodinated serum albumin and red blood cell (RBC) volume by radioactive chromium labeled autologous RBC. These two measurements are compared to calculate total blood volume. The accuracy of this technique is good in healthy individuals, but in sick individuals it is not very accurate due to loss of labeled albumin. The blood volume determination remains accurate because even in leaky capillaries RBCs, due to their size and shape, rarely leak out.Very large macromolecules such as FITC dextran are functionally similar to tagged RBCs. Because of their large size they do not leak out of the intravascular space even in subjects with capillary leak. They are stable over a period of several days and are easily quantified without the use of radioactivity.This invention is a method of determining the volume of plasma in a patient by introducing into the circulation a predetermined amount of biodegradable, nontoxic macromolecules. These molecules are sufficiently larger than endothelial junctions as to be incapable of leaking out of the patient's capillaries. Each macromolecule is labeled with a detectable marker such that, after a period of time sufficient for distribution of the macromolecules throughout the patient's circulatory system, a plasma sample can be collected and the concentration of the macromolecule can be rapidly determined. The known quantity of macromolecule introduced will allow total plasma volume to be calculated from the concentration. This invention has been tested using FITC dextran 2000k in both normal rats and rats in hemorrhagic shock and has been shown to be accurate in both cases.
Accurate in healthy and sick patients. Can be carried out without the use of radioactivity. Quick to administer and simple to detect with a relatively inexpensive flourometerOpportunities Development of labeled macromolecules Development of diagnostic package (injectable macromolecule solution and detection equipment)
Assay for determination of blood plasma volume
This invention is a method of determining the volume of plasma in a patient by introducing into the circulation a predetermined amount of biodegradable, nontoxic macromolecules. These molecules are sufficiently larger than endothelial junctions as t...
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