Our "In Vivo" process involves running a pre-transfusion plasma hemoglobin level on the patient and then giving the patient a 10 cc challenge of a donor unit. Approx 15 minutes after the challenge dose is given the patient's post-challenge plasma hemoglobin level is determined. If the difference in the post vs the pre levels is less than 10 mg/dl (I think those are the appropriate units) then we can infuse the rest of the unit. Washed cells are used for this to assure that any increase in plasma hemoglobin is due to active hemolysis and not from hemolysis in the stored donor unit.

Interesting. We've had a couple of patients it might have been worth trying on, but we don't have the ability to wash units.

Wouldn't the patient himself be able to supply plenty of complement for any hemolytic reaction? I remember when we used to add fresh serum in testing to make sure we had complement in the system. It didn't have to come from the donor or the patient.

I suppose a complement deficient person could be like an IgA deficient person and make an antibody to foreign complement and go into anaphylaxis.

According to Petz and Garratty, in the study that is often cited as a basis for transfusing washed red cells to CAS patients, the patient in question had a serum complement level that was "always low". The authors of that study speculated that the plasma transfused with the RBC unit provided enough complement for the hemolytic reaction the patient had following transfusion. (Kind of like adding complement to a test system, only this system was in vivo.) Petz and Garratty say that they would like more documentation of this sort of phenomena. They note that serum complement is ordinarily not reduced in warm- or cold- antibody AIHA. They think there should be more information available before routinely recommending washed red cells for these types of patients. I suspect that a number of things we do are based on shaky foundations like this.