The one unequivocal clinical indication for measuring a patient's ionised
calcium is during blood (etc) transfusion of a patient who is anhepatic.
There is a genuine risk of citrate toxicity.
This mainly applies during the course of a liver transplant surgical
operation, from the time of removal of the explant, until the donor liver
is connected and functioning.
In Cambridge, the dual risks of low iCa++ owing to citrate excess, and high
iCa++ owing to intravenous calcium replacement, are monitored via the blood
gas machine's iCa++ electrode; we still do this owing to adverse
experience in the early days of this procedure. The blood gas analyser in
Theatre is used.
A normal liver, or even a grotty one, is able to metabolise citrate avidly;
but any other cause of complete cell failure could have the same effect.
Citrate toxicity is also seen on transfusing a severely hypothermic
patient, presumably owing to slowed metabolism..
I agree that in other everyday clinical circumstances, the iCa++ results
seem to be used to treat the doctor or nurse, not the patient!
>During a recent audit of our NPT facilities, it became increasingly
>evident that, although ionised calcium was measured and recorded
>on the patient chart, almost always, no action is taken to correct
>or verify, (by sending a sample to the laboratory), even grossly
>abnormal results. Our Consultant Anaesthetists say they can't
>remember when they last thought a patient required a change in
>therapy on the basis of an ionised calcium (this included adult ICU, etc,,,
Dr Les Culank,
Consultant Chemical Pathologist.
Dept of Clinical Biochemistry, Addenbrooke's Hospital
Cambridge UK CB2 2QR
Tel: +44 (0)1223.217153 fax: 216862
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