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| Indocyanine Green Dye to Measure Cardiac
Output
and Blood Volume |
| Measurement of
blood volume is critical to understanding orthostatic stress and blood
circulation in general. The use of Indocyanine Green (also known as
CardioGreen) dye dilution technique is a standard, time honored method to
measure cardiac output and blood volume
. In the past it had been technically
difficult because it required continuous withdrawal of blood from an
arterial site for indicator assay. Indicator detection has been simplified
using noninvasive spectrophotometric methods with a finger photosensor (DDG,
Nihon-Kohden Inc), which have recently been implemented with excellent
results. The area under the photometric curve after a known amount of dye
is injected determines the cardiac output by Stewart’s historic method
. Extrapolation of the dye decay curve
yields measurements of blood volume. This is a limitation of this method
in comparison with non-first pass indicators. The dye is rapidly excreted
by the liver and its elimination can be used in the estimate of splanchnic
blood flow. It is inert, harmless, and can be given every 5 minutes
to reassess blood volume and cardiac output. Accurate measurement of blood
volume and overall cardiac output throughout experiments is an important
feature of our work. For example, blood volume changes during upright tilt
due to extravasation. Absolute blood volume is an important quantitative
piece of information that is difficult to measure repeatedly by any other
means. There is no better technique for assessing cardiac output without
using highly invasive methods.
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| Daxor: Blood Volume
by Radioactive Albumin |
| The principle here is simpler. A measured amount of tagged
albumin is given at time zero. The biological half life of he allbumin is
ling and thus the once distributed an accurate "albumin space may be readily
obtined by sampling the concentration of radioactivity. |
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Indicator Techniques to Measure Blood Volume and Cardiac Output