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Chapter 7: Functional description
Legend
Effect of the citrate
Limits of citrate
anticoagulation
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Fig.: Schematic of regional anticoagulation
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Blood pump
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Haemofilter
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Air detector
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Venous clamp
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Citrate pump
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Citrate drop counter
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Calcium pump
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Calcium drop counter
The citrate binds the ionised calcium that is present in the blood and
forms a calcium-citrate complex. The resulting reduction of the ionised
calcium concentration inhibits several steps in the coagulation cascade.
Regional citrate anticoagulation can have various consequences,
including a considerable reduction of the mutual activation of the
various vitamin K-dependent modified coagulation factors. The binding
of these coagulation factors to activated cell membranes requires
calcium which is bound to their GLA domain and is therefore only
possible with sufficiently high levels of ionised calcium.
Citrate anticoagulation does not prevent coagulation in the
extracorporeal blood circuit in all cases. This is possibly explained by
the fact that activated thrombin, as opposed to prothrombin
(thrombinogen, factor II), no longer has a GLA domain, which explains
why the mechanism discussed above cannot be effective with thrombin.
Fresenius Medical Care multiFiltrate IFU-EN-UK 15A-2015
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