Hepatic effects of the leaching of phthalate ester plasticizer and silicon

Particle Spallation and Plasticiser (DEHP) Release from Extracorporeal Circuit Tubing Materials

Particle spallation and plasticiser (DEHP) release from medical grade polyvinylchloride (PVC), co-extruded PVC-polyurethane (PIVIPOL)R and an experimentally produced co-extruded PVC-ethylene vinyl acetate (EVA) has been studied when used with manually occluded and self-occluding peristaltic pumps over a six hour pumping period. The shore hardness of the tubings studied were similar but the luminal coating thickness differed (0.2 mm polyurethane, 0.99 mm EVA).

The pattern of particle release was similar for all materials on the pump type used with the majority of particles released being less than 5 microns in diameter. The number of particles greater than 5 microns released was independent of the tubing material but depended on the pump type. Particle release with self-occluding pumps was significantly higher (p<0.001) than for the manually occluded pump. Scanning electron microscopy indicated that the particles released originate from the repeated compression and flexing of the insert during pumping which leads to material structural failure. The higher release observed in the case of self-occluding pumps is suggestive of over-occlusion by the springs utilised in the pump.

DEHP release (ppm) over a six hour period while perfused at 300 ml/min was significantly reduced for co-extruded tubing (0.56 ± 0.05 mg (PVC-polyurethane) and 0.12 ± 0.04 mg (PVC-EVA) compared with PVC (0.74 ± 0.05 mg).

Exposure of hemodialysis patients to di-2-ethylhexyl phthalate

The migration of di-2-ethylhexyl phthalate (DEHP) from dialyzers was studied in 21 patients with chronic renal failure undergoing maintenance hemodialysis. The circulating concentrations of DEHP were measured by high performance liquid chromatography in blood of patients obtained from the inlet and the outlet of the dialyzer during a 4-h dialysis session. During treatment of renal failure using plasticized tubing, the plasma level of DEHP increased. On average, an estimated 75.2 mg of DEHP was extracted from the dialyzer during a single dialysis session, with a range of 44.3-197. 1 mg. On the other hand, the total amount of DEHP retained by the patient during the dialysis session was evaluated by the difference between the AUCout and the AUCin and ranged from 3.6 to 59.6 mg. The rate of extraction of DEHP from the dialyzer was correlated (r=0.705, P<0.05) with serum lipid content (cholesterol and triglyceride).So, we confirmed that patients on hemodialysis are always regularly exposed to considerable amounts of DEHP. However, several metabolic effects have been reported in various animal species following treatment with DEHP, such as changes in lipid metabolism and in hepatic microsomal drug-metabolizing enzyme activities. DEHP is now a well-known hepatic peroxisomal proliferator in rodents and an inducer of many peroxisomal and non-peroxisomal enzymes. So, lipid metabolism modifications and hepatic changes observed in hemodialysis patients could be explained from chronic exposition to DEHP. In the coming years, it seems necessary to reconsider the use of DEHP as a plasticizer in medical devices. Highly unacceptable amounts of DEHP leached during the dialysis session could be easily avoided by careful selection of hemodialysis tubing.

Plasticizer extraction of Taxol infusion solution from various infusion devices

Taxol solution extracts the plasticizer DEHP (di(2-ethylhexyl)phthalate) from polyvinyl chloride (PVC) materials. In order to minimize patient exposure to DEHP, Taxol solutions should be prepared and administered in PVC-free materials. Particulate matter may form in Taxol infusion solution over time, so that in-line filtration with microporous membranes not greater than 0.22 microns is advisable. The purpose of this study was to evaluate the suitability of various administration- and in-line filter-sets for Taxol application. The extent of leached DEHP was determined using a Reversed Phase HPLC assay specific for DEHP. The four tested administration-sets, labeled as PVC-free, were all found to be suitable for Taxol application. The tested standard PVC-lined administration-set should not be used for Taxol application. Baxter Intermate LV 250 can be recommended as a disposable infusion device for ambulatory Taxol application. It can be connected with all the tested filter sets.

Biocompatibility issues in hemodialysis

Hemodialysis, as a life-saving treatment modality for uremic patients, implies a repeated and compulsory contact of blood with foreign materials. As a consequence, biocompatibility problems are unavoidable. The same applies for the material used for the creation of vascular access, and for the alternative dialysis method, CAPD (continuous ambulatory peritoneal dialysis), although each system might cause its own and specific problems. Although in early dialysis the focus has been on maintenance of life and elimination of toxins, later on the important morbid implications of this lack of biocompatibility have been recognized. Eight major problems will be discussed, especially in the perspective of recent new findings in this field: (1) coagulation and clotting; (2) complement and leukocyte activation; (3) susceptibility to infection; (4) leaching or spallation; (5) surface alterations of solid materials; (6) allergic reactions; (7) shear; (8) transfer of compounds from contaminated dialysate. After description of the major biochemical and clinical implications of these problems, ways to prevent morbid events and future perspectives will be described.

Effects of prolonged treatment with phthalate ester on rat liver

Rats were fed a diet containing 2%, 0.2% or 0.02% di(2-ethylhexyl)phthalate (DEHP) for a period of 102 weeks. Only the 2% diet caused a substantial decrease in body weight. Both peroxisomal palmitoyl-CoA dehydrogenase and mitochondrial carnitine acetyltransferase activities were greatly induced by exposure to the highest dose of phthalate ester, reaching maximal plateau values after about 20 weeks of treatment. The diet containing 0.2% DEHP increased both activities slowly, but continuously, and at the end of the two-year period these increases were almost comparable to those obtained with the highest dose. Even the lowest dose gave a slowly increase in these activities. Both microsomal NADPH-cytochrome c reductase activity and the level of cytochrome P-450 were increased initially by exposure to 2% DEHP, but returned almost or completely to the control level after about 30 weeks of exposure. Depending on the dose of DEHP in the diet, peroxisomal catalase activity was elevated above the control level during the first year of treatment but was about the same as in the control animals during the second year. A substantial decrease in peroxisomal urate oxidase activity was observed throughout the entire experimental period. When treatment was ceased after one year, all activities returned to the control values within 2-3 weeks. These results demonstrate the complex nature of the effects caused by prolonged treatment with DEHP with cumulative increases at low doses.

Extraction of diethylhexylphthalate from total nutrient solution-containing polyvinyl chloride bags

Total nutrient solution (TNS) is a new method for delivering total parenteral nutrition (TPN) by admixing dextrose, amino acids, and lipids in a single container. Recommendations are to use nonpolyvinyl chloride (PVC) containers for admixture of these solutions. PVC is a hard, brittle, and inflexible substance, and plasticizers, predominantly diethylhexylphthalate (DEHP), are added to impart flexibility. DEHP is a lipid soluble suspected carcinogen, hepatotoxin, and teratogen which has been shown to leach from PVC products containing lipophilic admixtures. The purpose of this study was to quantitate the amount of DEHP which leaches from PVC bags containing TNS. Six study groups, which contained three formulas stored at 25 degrees C +/- 2 degrees C and 4 degrees C +/- 1 degree C, were assayed for DEHP at time 0, 12, 24, 48 and 72 hr, 1 wk, and 3 wk using high-performance liquid chromatography. The control group contained an amino acid source, a carbohydrate source, and standard electrolytes, and the other groups contained a 10% lipid source or a 20% lipid source in addition to the constituents of the control group. Lipid-containing groups demonstrated detectable levels of DEHP at 48 hr, and DEHP content increased in these groups throughout the 21-day study. DEHP concentrations were lower in lipid-containing groups stored at 4 degrees C than comparable groups stored at 25 degrees C.

Improving the prognosis in acute renal and respiratory failure

We have achieved smooth homeostasis in patients with acute renal and respiratory failure by means of machine-controlled, continuous ultrafiltration and simultaneous bicarbonate hemodialysis with a polysulfone, biocompatible membrane (CUPID). No adverse effects were seen, even after 22 days of continued treatment. Mortality was reduced (7/14) when compared to that of a similar group given short conventional daily acetate hemodialysis and ultrafiltration with a cuprophane membrane (12/18).

The influence of prolonged di(2-ethylhexyl)phthalate treatment on the dolichol and dolichyl-P content of rat liver

Dolichols and glycosyl transferase activities were studied in rat liver fractions after treatment with the plasticizer di(2-ethylhexyl)phthalate, an inducer of peroxisomes and mitochondria. After a few weeks of treatment with 2% plasticizer in the diet, the amount of dolichol is more than doubled in the lysosomes but not in the microsomes while dolichyl-P decreased by 50% in the microsomes but not in the lysosomes. The isoprenoid pattern for dolichol and dolichyl-P, respectively, is modified to longer polyprenols in the two fractions as seen in the percent distribution of the individual isoprenes. Dolichyl-P and protein glycosylation by N-acetylglucosamine and mannose decreased considerably. Incubation with mixtures containing exogenous dolichyl-P did not increase protein glycosylation. Phthalate ester treatment for 2 years increased dolichol content above the control values even when the dose was decreased a hundred times, to 0.02%. The results demonstrate a compartmentalization of dolichol and dolichyl-P distribution, and the induction studies suggest that hepatocytes possess separate regulating mechanisms for these two compounds.

Phthalate esters and their effect on the liver

The advantageous properties of polyvinyl chloride plastics make these materials indispensable at all levels of human life, and there is no reason to believe that the upward trend of their use will change. One third of most polyvinyl chloride plastics consists of plasticizers, mostly phthalate esters, which may migrate out contaminating our environment and consequently our bodies. Experimental results indicate that chronic exposure to phthalic esters may be responsible for a number of adverse health effects. Phthalates change the structure and function of the liver in a profound manner by inducing peroxisomes, mitochondria and enzymes which participate in fatty acid transport and beta-oxidation. Prolonged administration of phthalate esters, in doses comparable to those occurring in human exposures, seems to have an accumulative effect on the liver. Liver biopsies taken from dialysis patients show peroxisome proliferation which again warn of the possibility that human health may be influenced by plasticizers.