Physical and thermal properties of blood storage bags: implications for shipping frozen components on dry ice.
BACKGROUND
Frozen blood components are shipped on dry ice. The lower temperature (-70 degrees C in contrast to usual storage at -30 degrees C) and shipping conditions may cause a rent in the storage bag, breaking sterility and rendering the unit useless. The rate of loss can reach 50 to 80 percent. To identify those bags with lower probability of breaking during shipment, the thermal and physical properties of blood storage bags were examined.


METHODS
Blood storage bags were obtained from several manufacturers and were of the following compositions: PVC with citrate, di-2-ethylhexylphthalate (DEHP), or tri-2-ethylhexyl-tri-mellitate (TEHTM) plasticizer; polyolefin (PO); poly(ethylene-co-vinyl acetate) (EVA); or fluorinated polyethylene propylene (FEP). The glass transition temperature (Tg) of each storage bag was determined. Bag thickness and measures of material strength (tensile modulus [MT] and time to achieve 0.5 percent strain [T0.5%]) were evaluated. M(T) and T0.5% measurements were made at 25 and -70 degrees C. Response to applied force at -70 degrees C was measured using an impact testing device and a drop test.


RESULTS
The Tg of the bags fell into two groups: 70 to 105 degrees C (PO, FEP) and -50 to -17 degrees C (PVC with plasticizer, EVA). Bag thickness ranged from 0.14 to 0.41 mm. Compared to other materials, the ratios of M(T) and T0.5% for PVC bags were increased (p < or = 0.001) indicating that structural changes for PVC were more pronounced upon cooling from 25 to -70 degrees C. Bags containing EVA were more shock resistant, resulting in the lowest rate of breakage (10% breakage) when compared with PO (60% breakage, p = 0.0573) or PVC (100% breakage, p = 0.0001).


CONCLUSIONS
Blood storage bags made of EVA appear better suited for shipping frozen blood components on dry ice and are cost-effective replacements for PVC bags. For the identification of blood storage bags meeting specific storage requirements, physical and thermal analyses of blood storage bags may be useful and remove empiricism from the process.
Hmel
Peter J
PJ
Department of Blood Research, Walter Reed Army Institute of Research, Silver Spring, MD 20910-7500, USA.
Kennedy
Anthony
A
Quiles
John G
JG
Gorogias
Martha
M
Seelbaugh
Joseph P
JP
Morrissette
Craig R
CR
Van Ness
Kenneth
K
Reid
T J
TJ
D001793:Blood Preservation / Q000191:economics / Q000379:methods*; D003365:Costs and Cost Analysis; D015925:Cryopreservation / Q000379:methods; D004367:Dry Ice; D006801:Humans; D008422:Materials Testing; D019563:Mechanics; D019064:Product Packaging / Q000191:economics / Q000592:standards*; D013696:Temperature; D013718:Tensile Strength; D014186:Transportation / Q000379:methods
D004367:Dry Ice