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7.3.2.5
Citrate accumulation
Insufficient citrate
metabolism and citrate
accumulation
Alkalosis / hypercalcaemia
after citrate
anticoagulation
Fresenius Medical Care multiFiltrate IFU-EN-UK 15A-2015
The systemically infused citrate is usually metabolised quickly. In
patients who have or develop a metabolic disorder for citrate, the
metabolism is slower. This results in an elevated systemic citrate
concentration. As the systemic citrate concentration is only measured
in exceptional cases in the hospital, it is assessed indirectly by its
effects.
The systemically accumulated citrate also binds calcium. As a
consequence, the percentage of ionised calcium in the total calcium
decreases.
Generally, the shift between systemic ionised calcium and total calcium
is first indicated by a drop of the systemic ionised calcium concentration,
which is properly corrected by increasing the calcium dose. A calcium
dose above 2.1 mmol/l (empirically determined) which is set on the
device can be indicative of possible citrate accumulation. The device
will show an appropriate message.
Note
If doses of up to 3 mmol/l of calcium per litre of filtrate are not sufficient
to stabilise the systemic ionised calcium concentration, citrate
accumulation must be assumed. In this case, citrate anticoagulation
must be stopped immediately.
After a stabilization of the systemic ionised calcium by an appropriate
calcium substitution, the shift in the concentration ratio of total calcium
to systemic ionised calcium is shown by an increased total calcium. This
increase is relative to the citrate accumulation, corresponding to the
calcium-citrate complexes circulating in the blood.
An increase of the concentration ratio of total calcium to systemic
ionised calcium above 2.5 is cited in literature as a sign of citrate
accumulation. However, this value should not be regarded a strict limit,
but as an aid for orientation.
Citrate accumulation may also cause a mild metabolic acidosis. This
can, however, also be a symptom of a variety of other causes and is
therefore not specific to a metabolic citrate disorder.
After completion of the treatment, the accumulated calcium-citrate
complexes are metabolised by the patient. This may result in alkalosis
and hypercalcaemia.
If clinically indicated, these risks can be reduced by continuing the
CRRT treatment without citrate anticoagulation.
Chapter 7: Functional description
7-27
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