Volume-Reduced Blood Products

Methods

Volume-reduced products are manufactured using a modification of the RBC component preparation method described in Chapter 10 . Volume-reduced method was described by Strauss et al. and enables manufacturing of small RBC aliquots, with a hematocrit of >90% using single RBC product until expiration on day 42, for neonates. Whole blood collected in CP2D is centrifuged at 5000 g for 5 minutes, the supernatant platelet-rich plasma is removed, and 100 mL of extended storage media, preferably AS-3 (as it does not contain mannitol), is added to and mixed with RBCs. The product is drained by gravity through a leukoreduction filter into a primary storage bag. Attached to this primary storage bag, by way of sterile connecting device, are a cluster of small volume bags. When an aliquot for transfusion is ordered, storage bag is centrifuged in an inverted position to pack the RBCs to a hematocrit of approximately 90%. RBC volume requested flows out into one of the attached small volume bags, which is subsequently disconnected. The remainder of the product is mixed and returned to storage. In addition, the product is mixed thoroughly each week.

A less complicated method of concentrating RBC products is by “inverted gravity sedimentation,” which does not require a refrigerated centrifuge. This method stores RBC products in the refrigerator “upside down,” which will concentrate an additive solution product to a hematocrit of around 70%–90% within 72 hours.

Indications

Two primary indications for volume-reduced RBCs are prevention of transfusion of unnecessary fluid to a volume-sensitive patient and removal of potassium-containing supernatant to prevent hyperkalemia in an at-risk patient. Volume reduction of RBC products to prevent passive transfusion of potentially hazardous concentrations of potassium applies only to large volume transfusions (≥20 mL/kg). Transfusion safety without volume reduction has been established by Strauss. Concentration of extracellular potassium in the supernatant depends on the age of the RBC product and when/if the product was irradiated. Extracellular potassium increases from ∼4 mmol/L at day 0 to ∼60 mmol/L at day 42 in a nonirradiated additive solution RBC product, or to 80 mmol/L at day 35 in a CPDA-1 RBC product ( Table 33.1 ). Therefore, a 1-kg infant receiving a 15 mL transfusion would only receive 0.3–0.4 mEq of potassium, which is a small amount compared with daily requirement of potassium of 2–3 mEq/kg. There have been several studies confirming lack of hyperkalemia or other untoward events for small volume transfusions of 42-day storage AS RBC products into neonates. There are individual patients, such as those with or at risk of hyperkalemia (i.e., small infants with only one vascular access point and tip of catheter near right atrium) and patients receiving large volume transfusion, who could be at an increased risk of transfusion-related hyperkalemia and may benefit from volume-reduced RBC products.

Adverse Effects

Volume reduction of RBC products does not appear to harm the RBCs. As the removal of supernatant can be performed in a closed system, expiration date of the product does not change.