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Biomedical subjects

R Popovich

Publications and source records attributed to R Popovich.

10 recordsLinked to original sources
PubMed1995

A new porous surface modification technology for peritoneal dialysis catheters as an exit-site cuff to reduce exit-site infections.

Catheter exit-site infection continues to be a more common morbid event in patients undergoing peritoneal dialysis. Previous attempts to place a biointegration material at the next site have failed to reduce infection rates. This study reports the use of an innovative microporous silicone material placed as a cuff around the catheter at the exit site. The porous material has a pore-sized distribution that stimulates and facilitates capillary ingrowth into the pores. This capillary ingrowth prevents scar tissue formation, increases blood supply, and theoretically improves the immunological competence of the tissue at the vulnerable exit site. Twenty-five test catheters (12 using standard exit-site creation and 13 using the Moncrief-Popovich implantation technique) were implanted in a canine model. The exit-site infection rate in a canine model without the microporous material was 100% at 2 months. The corresponding results with the microporous material was 40% at 2 months. The majority of the test catheters showed progressive drying and healing at the exit site. Sixty percent of the catheters healed quickly and remained infection-free. Biointegration of the microporous material at the exit-site was demonstrated. Several exit site infections with the test catheters treated only with local therapy (without systemic or topical antibiotics) demonstrated progressive healing and secondary adequate biointegration. Because of these encouraging results, human studies were initiated, with the first human implant occurring in August, 1994. A 10-patient project is planned for the next year.

Animals↗
PubMed1993

Catheter obstruction with omental wrap stimulated by dialysate exposure.

A new implantation technique and catheter design (Moncrief-Popovich Catheter) were tested in the continuous ambulatory peritoneal dialysis (CAPD) dog model. With this technique the catheter distal (external) segment was implanted in a subcutaneous tunnel for 4-6 weeks. Therefore, no irrigation of exposure to dialysate was present. Secondary exteriorization and irrigation (CAPD exchanges) demonstrated no episodes of primary catheter obstruction. Fifteen mongrel female dogs had 30 catheters implanted; 2 catheters simultaneously in each dog. One catheter was implanted with the interabdominal segments in the pelvis and the second interabdominal segment directed upward in direct contact with the omentum. Following initial irrigation, all catheters were patent, but within 24-48 hours all upwardly directed catheters were obstructed. Nine of the 15 downwardly directed catheters became obstructed by omentum wrapping around the catheter within 5 days. Preliminary studies have failed to demonstrate the cause of this "omental stimulation," which occurs with peritoneal contact with fresh dialysate. Possible explanations include pH, osmolality, flow direction, volume, vasodilator effect of osmols or lactate, and glucose, among others. This effect needs study, and this model would allow evaluation of improvements in the biocompatibility of dialysis fluids.

Animals↗
PubMed1980

New directions in peritoneal dialysis concepts and applications.

A limited number of peritoneal capillaries involved in solute exchange during peritoneal dialysis and inaccessible stagnant fluid films within the peritoneal interstitium may account for most resistance to solute transport during peritoneal dialysis. The control of small solute concentrations in blood by intermittent peritoneal dialysis will probably always require 30 to 40 hr/week of treatment even with the most rapid cycling devices. Increased understanding of factors that effect the microcirculation of the peritoneum may allow manipulation of protein losses and optimization of the long-term health of the peritoneum but will probably have little impact on the efficiency of small solute transport. CAPD accepts peritoneal dialysis as a low-efficiency system in terms of small solute clearances and yet yields similar weekly clearances to hemodialysis for small solutes by utilizing continuous dialysis. Large solute clearances with CAPD markedly exceed weekly clearances with hemodialysis.

Ambulatory Care↗
PubMed1978

Comparison of polymer, glucose, and hydrostatic pressure induced ultrafiltration in a hollow fiber dialyzer: effects on convective solute transport.

Ultrafiltration induced by (1) poly(sodium acrylate), (2) glucose, and (3) hydrostatic pressure was studied in a hollow fiber dialyzer. Poly(sodium acrylate) added to dialysate induced large amounts of ultrafiltration without crossing the dialyzer membrane. Sodium ions of the acrylate polymer were osmotically active but were held in dialysate by the impermeant anionic polymer. The hydrostatic pressure equivalent of osmotic pressure induced primarily by the sodium ions approximated that predicted for a completely impermeant molecule. The apparent (net) sieving coefficients for vitamin B12 observed during polymer and hydrostatic ultrafiltration studies were both significantly higher than that observed during glucose ultrafiltration but did not differ from each other. These studies suggest that sodium salts of polyanions can provide an osmotic driving force to yield large amounts of ultrafiltration in dialysis systems and yet not cross the membrane. The studies also suggest that relatively less efficient convective transport with glucose as compared to hydrostatic pressure is neither a membrane phenomenon nor a characteristic of all osmotic pressure induced ultrafiltration. Relatively low effective solute sieving appears to be associated with osmotic induced ultrafiltration with a permeant solute. Under such conditions it is proposed that molecular interaction within the membrane impairs convective transport.

Acrylic Resins↗
PubMedDate not supplied

Peritoneal membrane plasmapheresis.

A novel process has been devised that uses the peritoneal membrane to remove plasma proteins from the body at a rate comparable to conventional extracorporeal plasma-pheresis. A vasodilator (4 mg histamine phosphate) is added to 1 liter of hypertonic solution (485 mOsmol/L), and infused intraperitoneally with a residence time of 4 hr. Plasma containing proteins is convected across the peritoneum through open pores into the cavity and removed. The next alternating infusion is with a hypotonic solution (214 mOsml/L) containing a vasoconstrictor (1.0 mg norepinephrine). This infusion restores the fluid removed from the subject in the previous exchange, and prevents the rapid fall-off in protein removal rates obtained with repeated infusions with vasodilators only. Peritoneal membrane plasmapheresis was successfully tested on canines, with protein removal rates of between 30% and 50% of total serum protein per day for 13 days over a 22 day period. Peritoneal membrane plasmapheresis represents a potentially inexpensive, continuous/nightly home treatment for protein mediated diseases treatable by extracorporeal plasmapheresis.

Animals↗