Packed Red Blood Cells and Ionized Calcium

by Andria RN · 0 comments

in ICU,Uncategorized

The Preservatives in Packed Red Blood Cells eat our Calcium!

This post is pertinent for patients receiving multiple units of Packed Red Blood Cells (PRBC’s). Some examples are cardiac surgery patients, trauma patients who are hemorrhaging and patients with GI bleeds.

Packed Red Blood Cells contain a preservative called citrate. The citrate binds to calcium in the blood to prevent it from clotting. **Remember that calcium is involved during several steps of the clotting cascade so when citrate binds the calcium, the clotting cascade is interrupted and our PRBC’s will stay clot free.


So, if the citrate in the PRBC’s binds the calcium in that unit of PRBC- it is going to do the same thing to the patient’s serum calcium during the transfusion. That’s why you should always make sure your patients ionized calcium is normal before administering PRBC’s. Then the rule of thumb is to recheck ionized calcium after every 4 units of PRBC’s.

Ionized calcium is a separate lab test from serum calcium. Serum calcium values may be accurate in a healthy person because generally a healthy person’s serum calcium is about the same as the calcium absorbed in bones. An ICU, patient however, has factors that make serum calcium values an inaccurate measure of total calcium. Patients who will have inaccurate serum calcium levels include patients receiving IV fluids and those with low albumin. Ionized calcium levels can be obtained from an arterial blood sample or obtained from a green top on ice.

If your ionized calcium levels are low, replacement with either Calcium Chloride or Calcium Gluconate is required. Calcium Chloride contains a higher concentration of chloride, but Ca Gluconate can be given IV. Giving IV Calcium has a positive inotropic effect- meaning myocardial contractility is improved. **This makes sense if you think back to Anatomy and Physiology and you remember that heart muscle fibers use calcium at binding sites.

When you give the calcium IV, you will see a temporary improvement in your hemodynamics and may be able to titrate down your vasopressors. Sadly, when the heart muscles uses up the calcium, this effect will wear off.

See? We Need Calcium!

 

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