Principles of Measurement and Parameters
Page B-10
Operator’s Manual PiCCO
2
Version 3.1
5.3
Principle of ICG elimination detection
ICG has an absorption maximum of approximately 805 nm. The determination of ICG concentration within this
range (optical window) is not disturbed by other blood components.
The trend in ICG concentration over time is used to calculate the relative change in percent per minute. The
plasma disappearance rate (PDR) of ICG is a measure of the excretory capacity of the liver and thus global
liver function. It is influenced by the function of liver cells as well as the liver perfusion. Depending on the
patients underlying disease the PDR helps to assess the patient´s liver function and/or liver perfusion. As the
liver is part of the splanchnic area, splanchnic perfusion can be indirectly
estimated.
Figure 11: Schematic representation of the ICG elimination curve
The figure above shows a typical ICG concentration curve with the initial peak and its course over
500 seconds. The elimination measurement starts after thorough mixing of ICG with the circulating blood
volume. The starting point of the PDR measurement is determined dynamically dependent on the circulation
time derived from the first peak. The ICG curve analysis continues for five to ten minutes, dependent on the
quality of the curve.
The starting point represents 100%. The algorithm detects a percentage decrease per minute and indicates
the PDR in percent per minute.
NOTE
For information on the diagnostic drug, Indocyanine Green, please refer to the corresponding
SPC (summary of product characteristics) or PIL (patient information leaflet) of ICG.
5.4
Parameters of pulse oximetry and pulse dye densitometry
The following parameters are measured by pulse dye densitometry and pulse oximetry:
x
Arterial oxygen saturation
SpO
2
(%)
x
Plasma Disappearance Rate of ICG
PDR (%/min)
x
Retention Rate of ICG after 15 minutes
R15 (%)
