ADDENDA Oct. 27, 2001

11. One excerpt that is pertinent from the AABB's Collected Questions and Answers, 7th edition, pg 40-41 is as follows:

QUESTION:
"A new pediatric hematologist physician has joined our hospital staff and insists on transfusing only platelets that are volume-reduced. Our Blood Bank staff, including our Medical Director, feel that volume-reduced platelets would only be warranted if the platelet unit contains plasma incompatible with the infant's ABO type. Since we only transfuse ABO/Rh type-specific platelets to infants, we think volume reduction is not only unnecessary, but reduced-volume platelets have decreased viability/efficacy. We suggest that if volume-overload is a concern, that they transfuse a smaller volume of platelet concentrate vs. volume-reduced. Does the physician have a valid reason for requesting volume-reduced platelets? "

RESPONSE:
"Few facilities routinely volume reduce platelets for neonatal patients when unable to obtain ABO-specific platelets. Neonates generally require a portion of an apheresis platelet or less than one unit of a platelet concentrate. According to McCullough, the volume of a platelet transfusion should be based on the size of the infant and the infant's platelet count. Examples of dosing strategies include:

• 1 unit of platelets per 10 kg of body weight
• 4 units of platelets per square meter of body surface area
• 10 mL of platelets per kg of body weight.

In most cases, a relatively small volume of platelets would be expected to adequately raise the platelet count. For example, given a 4 kg infant with a blood volume of 320 mL (80 mL/kg) with a hematocrit (Hct) of 50%, the plasma volume would be:Blood volume x (1 - Hct) = 320 x (1 - 0.50) = 160 mL If a routine platelet contains 3 x 10¹¹ platelets in 200 mL of plasma (an apheresis platelet). This would results in 1.5 x 10⁹ platelets per mL. If one allowed for a 50% in-vivo recovery of infused platelets one can calculate that relatively small volumes of platelets would result in substantial platelet increments. Thus, even small volumes such as 20 or 40 mL relative to the child's blood volume would result in substantial increments in the platelet count. Such arguments have been used as justification for not volume-reducing ABO identical platelets in this setting. (Reference: McCullough, J. Transfusion Medicine. McGraw-Hill, 1998, p.296 )

12. A blood banker at Children's Hospital of Philadelphia comments that they occasionally receive requests for volume-reduced platelets. All orders of this type must be approved by the Blood Bank Medical Director. Typically they prepare this product for patients who are very sensitive to additional fluids. They give these products a four-hour expiration date. The medical director and the ordering physician decide on the final volume, usually they will take a 1/4 of a unit down to 20-25 ml. They might do this once or twice a year. According to the responding blood banker, they do not wash platelets. They do remove the plasma and resuspend the platelets in saline if the donor is incompatible with the recipient. They give saline-suspended platelets a four-hour expiration date from the time they start to prepare the product.

13. A blood banker at Children's Hospital in Denver comments that one approach is to split a unit of platelets and transfuse the aliquots several hours apart to mitigate fluid overload. A sterile connection device makes this approach quite manageable. Her center routinely aliquots pheresis platelets for babies in this very manner.

14. A blood banker at Yale would like to respond to the "blood banker in Michigan" (reply #8) about the lack of data that "There was no published literature or evidence-based medicine that conclusively showed that this practice was of clinical benefit" The Yale blood banker offers the following references:

• Pisciotto PT, Snyder EL, Napychank PA, Hopfer SM. In vitro characteristics of volume-reduced platelet concentrate stored in syringes. Transfusion 1991;31:404-8

• Pisciotto PT, Snyder EL, Snyder JA, Frattaroli S, Hopfer SM, Rinder HM, Smith BR. In vitro characteristics of white cell-reduced single unitplatelet concentrates stored in syringes. Transfusion 1994;34:407-11.

Please submit comments to the e-Network Forum.

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