Supporting neonates with plateletpheresis units

A transfusion medicine physician at an academic center in Northern California has observed that with the movement to provide 100% leukoreduced blood components and the impending requirement for systems to detect bacteria in all platelets, blood centers that supply her hospital are phasing out production of whole blood-derived platelets. Consequently, her hospital is trying to develop protocols for supporting neonates with plateletpheresis units. They consulted colleagues at several institutions who informed them that they use sterile docking devices to transfer 10 mL/kg aliquots from plateletpheresis units into transfer bags or syringes, with apparently no limit placed on the number of aliquots taken from the main bag. However, the inquiring physician has been informed by a manufacturer of one of their plateletpheresis collecting devices that the minimum plasma volume that must be maintained in the original plateletpheresis storage bag is 100 mL. This suggests to the inquiring colleague that they can only take aliquots that total up to about 1/2 of the original platelet product. The inquiring physician would appreciate hearing some examples of protocols that use plateletpheresis units to support neonatal transfusion, specifically addressing any minimum storage requirement in the original bag.

Related questions include:

• does anyone aliquot a plateletpheresis product into multiple PL732 or similar bags designed for whole blood-derived platelets, and store the aliquots for 5 days in the smaller bags; if so, has the FDA reviewed this practice?
• if you need platelets for a baby and have only pheresis platelets with plasma that is ABO-incompatible with the patient, do you have a protocol for volume-reducing aliquots of plateletpheresis platelets? (The inquiring colleagues hospital limits the volume of ABO-incompatible plasma infused to 5 mL/kg)
• if you do not aliquot pheresis platelets but instead commit 1/2 of a pheresis product for each neonatal transfusion, do you have a protocol for volume-reducing 1/2 pheresis products; if so, into how much volume do you resuspend the packed 1/2 pheresis unit?

The following responses have been received.

ADDENDA July 22, 2004

1. A colleague in Albuquerque reports that they are also struggling with the issue of splitting plateletpheresis products for neonates. They are also under the impression that a minimum volume for a split depends on the bag in which the blood product was collected. She is of the impression that some bags have a minimum volume requirement of 100 mL and others have a minimum volume requirement of 150 mL. Without going into the math, they have figured that they could aliquot 50 mL from a 200 mL plateletpheresis product, so that there is at least 150 mL remaining in the original container, which would contain a therapeutic dose of platelets, per their policy. They issue the 50 mL aliquot soon after preparing it, since they do not believe that they can store such a small aliquot for an extended period of time. They do not issue smaller aliquots.

ADDENDA July 24, 2003

2. Several colleagues have inquired as to why a manufacturer has given a recommendation for maintaining minimum plasma volume in an apheresis bag. In particular, a colleague in Texas was wondering if you are taking out platelets with plasma during each draw from the bag, would not the proportion of plasma to platelets still remain the same? Are these bags any different than random (whole blood derived) platelet bags that contain > 40-50 mL volume?"
   
   The following response from an industry scientist shows that what may seem obvious on the surface may not always be correct, once data are obtained. According to Larry J. Dumont, Scientist at Gambro BCT, Inc., (attribution used with permission) Gambro recommendations for platelet storage in gas permeable bags (a.k.a., COBE/Gambro ELP bag) are associated with a lower volume and platelet concentration limit. He states (verbatim) "Our recommendations do not represent a critical cut-off, since platelets can be expected to store adequately outside of these limits. However, one can expect an increased risk of failures (principally pH) outside of these recommendations. Additionally, let me be quite clear that our recommendations are for 5 full days of storage at 22°C (standard blood banking conditions). For shorter hold times in our bag, the effect of volume and platelet concentration will be reduced. As the volume of the platelet product decreases, a larger surface area to volume ratio is created. This will allow the CO2 content of the bag to drop more quickly. When CO2 is depleted, there is no residual buffer capacity (bicarbonate) remaining to deal with the lactic acid produced by platelet glycolysis. Thus, a rapid drop in pH < 6.2 will ensue with negative effects on the platelet. The pH will initially rise as CO2 escapes the bag. This may have an impact on the platelet at very high pH values, although the evidence for this is quite weak (cf. Transfusion 2003;43:143-150). The platelet also provides a source of CO2 during storage - through bicarbonate buffering of lactic acid and also from the Kreb's cycle. When the platelet concentration is very low, this CO2 source will be compromised and total CO2 will be depleted much sooner. To counter these effects in a full sized bag, one may use a small surface area bag or a bag with lower gas permeability (a material property). One such approach which has been taken for 60mL platelets stored in the ELP bag is reducing the surface area by folding. This is reported in Transfusion 2000;40:91-100 and Transfusion 2002;42:1333-1339. Small volume platelets (~30-60mL) could also be transferred to small, single unit platelet storage bags which may be available from various suppliers. You may also be interested in work by Pisciotto et al. who reported on the effects of holding small platelet aliquots in polypropylene syringes for up to 6 hours, Transfusion 1994;34:407-411."

Submit comments to the e-Network Forum at enetworkforum@cbbsweb.org

Ira A. Shulman, MD
CBBS e-Network Forum Senior Editor & Moderator

W. Tait Stevens, MD
CBBS e-Network Forum Editor & Moderator

Elizabeth M. St. Lezin, MD
CBBS e-Network Forum Associate Editor & Moderator