Hct of packed RBCs

[dalangsfor]

Standards says that the hematocrit of packed RBCs must be <=80%. The technical manual also says (pg.805) that after the addition of additive solution the hct should be within 55 and 65%. What are some of your packed RBC hematocrits?

Thanks

[Lcsmrz]

The <80% standard comes from non-additive units. The hct should be <80% before the additive is introduced and about 60% afterwards.

Hcts will vary on the processing. Soft spins will have a lower hct than hard spins. Making Source Leuko's adds to the equation, too. To maximize your plasma yield with additive bags, keep the hct's as high as feasible.

[dalangsfor]

I use a Beckman J6 series centrifuge. I have trouble obtaining a hct >55% consistently with our cold units although my plasma and packed cell volumes are good. What type of centrifuge do you use and what spin time and speed do you use.

After the additive solution has been added, i mix the unit, strip the collection line, and obtain a sample for hematocrit. We run the sample on a Coulter cell counter. Any suggestions?

Thanks

[Lcsmrz]

We used a Sorvall. Assuming you don't make Platelets or Leukocytes, there is a procedure in the back of the Tech Manual for calibrating your centrifuge.

There are plenty of variables, from the type of bag you use and how much you fill it to how much you sqeeze off after a hard spin. Handling the units gently out of the centrifuge will make sure units stay packed. Also, auto units may be different from allogeneic.

I've used calibrated spun hcts, but a Coulter counter should be OK at hcts of 55%. Sampling technique sounds reasonable - make sure you remix the unit after stripping and before refilling the tubing.

[OPUS104]

RC3C Sorvall.......avg. 61 hct.

[dalangsfor]

today i spun cold units at 4200 rpm for 15 minutes. The highest hematocrit I got was 53%??? Does it matter what type of bag we collect it in. We use a 450 ml bag, 100 ml Additive solution and our anticoagulant is CPD. Not sure what is wrong. My RBC volumes after addition of ADSOL were all <350 and my plasma volumes were all 275 or greater.

Thanks

[Lcsmrz]

53% after additive sounds good to me! If prior to adding, it sounds a bit weak.

So many variables beyond time & RPM: centrifuge, what components are made, the type of bag, how full you fill 'em, how "shaken" the units are on removal, sampling technique, etc, etc. I'm assuming that the centrifuge time & speed tested OK -- the J6 is a nice device.

After weighing the full bag and with 15mins @ 4200 and no brake (max packing ability?), very gentle handling, extracting all plasma (buffy coat layer starts into the tubing), your should be able to weigh resulting rbcs & plasma to get an estimated hematocrit, then check it against your sampling (strip, mix, release, repeat twice, seal and test.) If they are within 5-10%, the sampling technique is probably accurate, and only changes to your centrifuge settings will increase the Hct toward some maximum possible value. Add additive and repeat sampling to check the final hct.

I suppose you can use the predonation Hct to calculate what the unit should be, then check what you actually got. Don't forget to adjust for the bag weight and the volume of CPD.

Sounds like a great project for an MT student in the BB rotation !!

[rcurrie]

We use Sorvalls also. It sounds like your centrifuges need calibration. We have no trouble at all hitting 60% 100% of the time for all 3 of our centrifuges.

Your processing techs also may be leaving too much plasma on the cells in the first place. If you are using the finger width rule of thumb (heh heh) to gauge the amount of plasma to leave on the cells, it might be time to move Fat-finger Frank over to another part of the lab from the FFP production section ;-)

BC