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Spallation and Plasticizer Release from Hemodialysis Blood Tubing: A Cause for Concern?

Routinely used extracorporeal circulatory procedures such as hemodialysis expose the blood repeatedly to foreign materials. Similar exposure also occurs in the case of less-frequent procedures, such as cardiac bypass surgery, plasmapheresis, and blood transfusion. The major portion of plastics used in these applications is polyvinyl chloride (PVC). The flexibility of PVC is achieved by the addition of a plasticizer, di(2-ethylhexyl) phthalate (DEHP). This phthalate ester may constitute up to 40% of the total PVC content of the item. The phthalates are physically linked but not chemically bound to the plastic and, in consequence, may be leached out into products that come in contact with the plastic ( I , 2). Their presence has been demonstrated in both plasma and red blood cells after PVC exposure (35) . Extracorporeal circulatory procedures rely on the use of peristaltic pumps to generate the flow through the circuit. Although a number of pump designs are in clinical use, their mode of operation is similar. The repeated flexing and compression of the segment of tubing for pumping by the pump rollers result in the abrasion and cracking of the internal surface of the segment. This leads to the shedding or spallation of particles into the extracorporeal circuit. The biocompatibility of extracorporeal procedures such as hemodialysis has received considerable attention of late. Much of the published work has focused on the role of the membrane (6) and the sterilization process (7) in modulating biocompatibility while, more recently, attention has shifted to the quality of water and the dialysate used (8). In contrast, blood tubing has been less intensively studied. Whether particle spallation and plasticizer release associated with the repeated use of hemodialysis tubing sets in end-stage renal disease patients is a cause for concern is a question that remains unanswered.