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.
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.


Peripheral Vascular Properties Measured by Strain Gauge Plethysmography (SPG)
Laser Doppler Flowmetry (LDF)
Indicator Techniques to Measure Blood Volume and Cardiac Output
Heart Rate and Blood Pressure
Near Infrared Spectroscopy
Microneurography and Muscle Sympathetic Nerve Activity (MSNA)
Transcranial Doppler Ultrasound (TCD)
Impedance Plethysmography (IPG)
Skeletal Muscle Pump