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Chapter 7: Functional description
Immediate availability of
the systemic ionised
calcium and acid-base
status measurement
Sample collection /
systemic blood sample
7-20
The determination of the systemic ionised calcium can be interpreted as
usual and is used to check the calcium substitution. The measurement
of the ionised calcium in the extracorporeal blood circuit (downstream
of the citrate infusion site, as seen in flow direction) is used to verify the
effect of the citrate. Here, the decrease in ionised calcium concentration
must be distinct.
Note
During the treatment, the analyzer for determining the acid-base status
and the concentrations of ionised calcium must be in the immediate
vicinity so that results are directly available.
For example, in intensive care units, this can be done with an automatic
blood gas analyser, which can also measure ionised calcium.
If the patient has an arterial access (e.g., for collection of blood samples
from artificially ventilated patients or for invasive blood pressure
measurement), the blood sample to check the systemic ionised calcium
and the systemic acid-base status should be taken there. Values which
may have been measured to control mechanical respiration can be
used.
Alternatively, the sample can be collected on the venous side if the
patient does not have an arterial access. This must be considered in the
interpretation of the acid-base values. Here, a collection site separate
from the extracorporeal blood circuit is recommended.
Alternatively, the blood sample can be taken slowly from the sampling
site (red) of the access line while the blood pump is running.
Note
If the sampling site on the access line is used, it must be ensured that
the blood pump is running while the sample is collected and that the
blood sample is aspirated slowly to prevent citrate from being admixed
by the citrate infusion.
In case of recirculation in the area of the catheter, blood which has just
been returned will enter into the aspirated blood, along with some
citrate. This addition of citrate leads to incorrect measurement values
for the systemic ionised calcium.
Fresenius Medical Care multiFiltrate IFU-EN-UK 15A-2015
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