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Biomedical subjects

P Ivanovich

Publications and source records attributed to P Ivanovich.

At least 37 records · Page 2Linked to original sources
PubMed1993

Dialysis-induced hypoxaemia.

A crossover study to compare the effects of seven different dialysers on blood gas conditions during dialysis using acetate-containing dialysate was carried out at five centres in four countries. A significant decrease in pO2 was noted at both 15 and 60 min after the start of dialysis for all dialysers, with the greatest decrease at 60 min. Filtral caused the greatest reduction and F 60 the least change at both 15 and 60 min. These differences were statistically significant according to the ANOVA multiple-range test for variance. pCO2 also declined by 1.0-2.7 mmHg at 15 min and by 0.7-3.8 mmHg at 60 min. The delta pCO2 was comparable across dialysers and no significant differences were found. Although pH showed no change at 15 min, it was slightly but significantly increased at 60 min across all dialysers compared to predialysis values. There were no statistical differences between dialysers. Calculated blood bicarbonate content significantly decreased at 15 min and recovered at 60 min. Along with the greater decrease in pO2, a larger loss of total CO2 was noted for Filtral. On the other hand F 60 caused the least change in total CO2. This difference may be due to membrane characteristics affecting the diffusion coefficient for O2, CO2, and bicarbonate. Multifactorial mechanisms are likely to be involved, but reflex hypoventilation and an increase in O2 consumption also contributed to hypoxaemia in this study.

Acetates↗
PubMed1993

Behaviour of white blood cells and the complement system.

Seven different types of dialysers were investigated in five dialysis centres in four countries with respect to behaviour of white blood cells and the complement system. The results of this controlled crossover study demonstrated significant differences in the dialysers. Those containing cuprammonium cellulose (G10-3N and G120 M) showed the greatest changes in white blood cell count, including monocytes and neutrophils, as well as the greatest complement activation. With regard to lymphocytes the subpopulation of low-mobility cells, which were predominantly the B-cells, showed the greatest mobility with dialysers containing cuprammonium cellulose. The PAN copolymer- and PMMA-containing dialysers Filtral and T 150 clearly caused the least changes in white blood cells and complement factors. Dialysers containing cellulose acetate and polysulphone membranes (Duo-Flux Artificial Kidney, CD 4000, and F 60) produced only a moderate decrease of WBC, monocyte, neutrophil, and lymphocyte counts, and this result corresponded to a relatively small change in complement factors.

Acrylic Resins↗
PubMed1993

Endothelium: the next frontier in biocompatibility.

Vascular endothelium plays a central role in two specific functional systems. It controls vascular tone, hemostasis, and substance transport. The endothelium is the "docking station" for trapping, deactivation, and regeneration of activated blood compounds and provides the principal clearance mechanism for biologically active mediators released by different cell types. The second function is a regenerational one. During the period between insults (or between dialysis sessions), the endothelium has to restore the "first line of defense," that is, to regenerate the injured athrombogenic surface of the vessel wall and its antioxidative potential, defoliate damaged endothelial cells, and interpolated new ones. These two important endothelial activities are required over and above its basic functions. Future research in artificial organs must take into account that continuous or intermittent blood-membrane contact creates an altered endothelial response. These altered responses may result in adaptional reactions that may differ substantially in the acutely ill patient on continuous venovenous hemofiltration (CVVH) or in a stable patient on maintenance hemodialysis. By a reduction in such factors as immediate or delayed cell-cell interactions (direct or indirect), it may be possible to influence the long-term outcome of chronic hemodialysis patients. Other research should strive to enhance those factors of endothelial function that are essential in the defensive and restorative properties of endothelial tissue. This is especially important in such continuous therapies as CVVH, long-term membrane oxygenation, and artificial heart and blood vessels. Currently, there are more unanswered questions than possible answers concerning endothelial functions in long-term hemodialysis patients, but it is clear that excluding endothelial cell behavior from investigation of extracorporeal therapy in the future would be a substantial omission.

Animals↗
PubMed1991

Inhibition of complement activation with EDTA in vivo during sham hemodialysis.

To check whether in vivo EDTA prevents complement activation resulting from blood contact with the dialyzer membrane, sham hemodialysis (HD) was performed in seven healthy volunteers using Cuprophan hollow-fiber dialyzers. Blood samples were drawn from the arterial and venous blood lines of the dialyzer before and after EDTA was infused into the arterial line. Venous line plasma C3a concentrations before EDTA infusion were significantly higher than after EDTA. Also, venous line plasma C3a concentrations before and after EDTA infusion were significantly higher than in the arterial line. These results indicate that complement activation can be attenuated by EDTA during sham HD. Technical improvements in the procedure may permit complete inhibition of complement activation.

Adult↗
PubMed1990

Beta 2-microglobulin elimination characteristics during hemofiltration with acrylonitrile and polysulfone membrane hemofilters.

Elimination characteristics of beta 2-microglobulin (BMG) during hemofiltration (HF) with acrylonitrile (AN69) and polysulfone (PS) hemofilters were investigated in a prospective clinical investigation. Seven chronic uremics on regular HF were treated for 4 weeks, three times a week, with AN69 hemofilters. The study was then repeated with PS hemofilters. There were no significant differences in the patients' body weight, the ultrafiltrate volume per session, and the duration of each HF session between both treatments. At the start of HF, arterial plasma concentration of BMG was (for AN69) 33.5 +/- 4.0 mg/L (mean +/- SD) and (for PS) 35.8 +/- 6.5 mg/L (NS); at the end of HF it was (for AN69) 11.0 +/- 1.8 mg/L and (for PS) 17.5 +/- 4.2 mg/L (p less than 0.001). The amount of BMG in total ultrafiltrate was (for AN69) 179.3 +/- 22.6 mg and (for PS) 140.6 +/- 26.8 mg (p less than 0.02). With AN69 hemofilter, maximum BMG plasma clearance and sieving coefficient were 51.0 +/- 9.5 mL/min and 0.42 +/- 0.04 at 60 minutes. With PS hemofilter, maximum BMG plasma clearance and sieving coefficient were 37.4 +/- 5.7 mL/min and 0.27 +/- 0.03 at 15 minutes. Twenty-two percents of BMG entering the AN69 hemofilter at 15 minutes were adsorbed on the membrane (p less than 0.001). BMG elimination with the AN69 hemofilter was more efficient than with the PS hemofilter. Long-term studies will be necessary to demonstrate whether this difference is of any clinical significance.

Acrylonitrile↗
PubMed1990

Anaphylatoxins C3a and C5a adsorption on acrylonitrile membrane of hollow-fiber and plate dialyzer--an in vivo study.

We studied the adsorption of anaphylatoxins C3a and C5a on acrylonitrile (AN69) hollow-fiber (AN69HF) and plate (AN69P) dialyzers in 8 patients during 4-hour hemodialyses (HD). Blood passed first through a cuprophan dialyzer and then through AN69 dialyzers that were not in contact with dialysis fluid. Plasma C3a and C5a were measured in samples taken from the afferent and efferent blood lines of the acrylonitrile dialyzers at 15, 60 and 240 min. Plasma C3a concentrations decreased significantly in blood that had passed through AN69 dialyzers. This decrease, indicating membrane adsorption, was maximal (by 65% in AN69HF and by 59% in AN69P) at 15 min and minimal (by 53% in AN69HF and by 18% in AN69P) at 240 min. The decrease in plasma C5a concentrations was smaller and significant throughout HD only with AN69HF. The amount of C3a adsorbed was at least 45,000 micrograms in AN69HF and 18,000 micrograms in AN69P. These findings demonstrate that acrylonitrile dialyzers adsorb more C3a and C5a than they produce. This membrane adsorption may explain why the increase of plasma C3a and C5a is inhibited during HD.

Acrylonitrile↗
PubMed1989

Recombinant human erythropoietin in nephrology.

rEPO therapy provides a unique opportunity to correct anemia in end-stage renal failure patients. Complete correction of the anemia, although possible, has some obvious disadvantages over a partial correction with a target hemoglobin of 10-13 g/dl or a hematocrit of 30-35%, respectively. Unresponsiveness to rEPO seems to be rare; in most cases the predicted hemoglobin increase could be seen as soon as an underlying iron deficiency was treated adequately. Blood loss and aluminum toxicity are the next most frequent reasons for an inadequate response to rEPO. Hypertension (and its complications) as well as fistula clotting are the most important side-effects which require close attention when patients at risk for these complications are treated with rEPO.

Acute Kidney Injury↗
PubMed1989

Optimization of hemofilters for the development of implantable artificial kidneys.

The concept of developing an implantable artificial kidney demands, in addition to the regeneration of endogenous filtrate, a small hemofilter with a high filtration rate. Conventional capillary filters are limited in their capacity to yield adequate filtrate, even if the number of capillaries is increased. To improve filter design so as to modify flow conditions for filtration rate augmentation, it is necessary to consider such factors as blood flow through a single capillary, wall shear rate, and transmembrane pressure (ptm) in in vivo applications, where such biological considerations as blood pressure, blood flow, and flow characteristics of blood are important. These requirements lead to a completely new filter type, the "curl filter," characterized by a large effective filtration surface in a relatively small number of hollow fibers in which optimal flow conditions prevail.

Equipment Design↗