Raleigh A Carmen

The Selection of Plastic Materials for Blood Bags

The procedures used in the preparation of blood components together with the processes used in the manufacture of multiple blood bag systems impose a unique combination of requirements that severely limits the selection of plastics. Plasticized PVC, the plastic used in the first blood bags introduced by Carl Walter over 40 years ago, remains the material of choice today. Blood bag material research has focused on two areas: (1) the development of containers with increased gas permeability for the storage of platelet concentrates; and (2) the reduction or elimination of plasticizer contamination of stored blood components. This research has led to the development of several second-generation containers that have improved the quality and extended the allowable storage period of platelet transfusion products. Plastics virtually free of extractives are available for the storage of platelets and plasma, but elimination of plasticizers from RBC products has not yet been achieved.

Survival of Red Cells Stored for 21 and 35 Days in a Non‐Di‐(2‐Ethylhexyl)Phthalate Plastic Container

Abstract. Whole blood and red cells were stored using citrate‐phosphate‐dextrose (CPD) and citrate‐phosphate‐dextrose‐adenine (CPDA‐1) anticoagulants in polyvinylchloride bags made flexible with di‐(2‐ethylhexyl)phthalate (DEHP) or tri‐(2‐ethylhexyl)trimellitate (TOTM) plasticizers. After storage the posttransfusion viability of these cells was tested in autologous donors. Cells stored in TOTM‐plasticized film had a survival rate less than 75% when stored for 35 days, while other systems had a survival greater than this. When compared with the red cells stored in CPD‐DEHP‐plasticized film, the viability of whole blood and red cells stored in CPDA‐TOTM showed a statistically significant decrease (p = <0.01). Therefore, red cell storage in TOTM‐plasticized PVC with current anticoagulant should be limited to 21 days.

Reduction of ball variance in silicone rubber occluders

all variance was a major cause for concern early in the B use of heart valves with silicone rubber occluders [l, 21. Ball variance can be defined as the physical changes that can occur in vivo accompanying the absorption of simple and complex plasma lipids. The changes are manifested in several ways, including discoloration, weight gain, wear, swelling, and fissuring. Valve function can be compromised by reduced occluder mobility, or by impaction or loss of the occluder. The SCDK and the Smeloff-Cutter (S-C) valves are double-cage ball valves in which the ball passes through the orifice of the valve, with the equator of the ball essentially occluding the valve orifice. Ball variance is of particular concern because the relationship of the diameter of the ball to that of the orifice must be maintained to assure optimal valve function. Clinical evidence of ball variance was reported in about 2.5% of the SCDK and in about 1% of the early model S-C valves. Because of the relatively low incidence of variance, we believed that both chemical and physical or environmental factors are involved in the development of ball variance. A major factor appears to be aberrant flow patterns in the prosthesis. Data on early Starr-Edwards valves showed that variance occurred only in the aortic position, where turbulence and impact forces were relatively great, and usually were associated with implantation problems, whereas paired mitral implants showed no variance [2]. On this basis, the problem was approached from several angles.