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Zbylut J Twardowski

Publications and source records attributed to Zbylut J Twardowski.

17 recordsLinked to original sources
PubMed2006

Treatment time and ultrafiltration rate are more important in dialysis prescription than small molecule clearance.

Chronic hemodialysis sessions, as developed in Seattle in the 1960s, were long procedures with minimal intra- and interdialytic symptoms. Over the next three decades, dialysis duration was shorten to 4, 3, even 2 h in thrice weekly schedules. This method spread rapidly, particularly in the United States, after the National Cooperative Dialysis Study suggested that the time of dialysis is of minor importance as long as urea clearance multiplied by dialysis time and scaled to total body water (Kt/V(urea)) equals 0.95-1.0. This number was later increased to 1.3, but the assumption that hemodialysis time is of minimal importance remained unchanged. However, Kt/V(urea) measures only the removal of low molecular weight substances and does not consider the removal of larger molecules. Nor does it correlate with the other important function of hemodialysis, namely ultrafiltration. Rapid ultrafiltration is associated with cramps, nausea, vomiting, headache, fatigue, hypotensive episodes during dialysis, and hangover after dialysis; patients remain fluid overloaded with subsequent poor blood pressure control leading to left ventricular hypertrophy, diastolic dysfunction, and high cardiovascular mortality. Kt/V(urea) should be abandoned as a measure of dialysis quality. The formula suggests that it is possible to decrease t as long as K is proportionately increased, but this is not true. Time of dialysis should be adjusted in such a way that patients would not suffer from symptoms related to rapid ultrafiltration, would not have other uremic symptoms and most patients would have blood pressure controlled without antihypertensive drugs.

Body Composition↗
PubMed2006

Pathophysiology of peritoneal transport.

The peritoneal membrane has the surface area similar to the body surface area. It consists of mesothelial cells, interstitium, connective tissue fibers, blood vessels, and lymphatics. Solutes of various sizes traverse the peritoneal membrane through at least three various pores: 'large' pores located in the venular interendothelial gaps, small 'paracellular' pores, and ultrasmall, 'transcellular' pores or aquaporins localized in peritoneal capillaries and mesothelial cells. High molecular weight solutes are mass-transfer limited; thus, their clearances do not increase significantly with high dialysate flow. Clearances of small molecular weight solutes are dialysate flow limited. Ultrafiltration is proportional to the hydrostatic and osmotic transmembrane pressures. The peritoneum offers greater resistance to accompanying solutes than to water (solute sieving), so that the concentration of solutes in the ultrafiltrate is less than in plasma water. Sodium sieving leads to hypertension, which is frequently observed in patients treated with short-dwell or continuous flow peritoneal dialysis. Peritoneal equilibration test is the most commonly used test to characterize peritoneal function and select the most suitable dialysis technique for a patient. Long-term peritoneal dialysis is associated with progressive loss of ultrafiltration capability due to structural and functional alterations in the membrane mostly as the consequence of exposure to glucose degradation products or advanced glycation end products generated during the sterilization process.

Biological Transport↗
PubMed2006

Peritoneal access: the past, present, and the future.

In the early years of peritoneal dialysis, there was no specific device for peritoneal dialysis; rather the devices used in general surgery and urology were taken advantage of for peritoneal access. These early devices, used for short-term peritoneal dialysis, were plagued with multiple complications, such as pressure on intestines of rigid tubes, plugging of openings, leakage of fluid around the access, and difficulties in fixation of the tube on the abdominal wall. In the late 1940s, after World War II, multiple peritoneal dialysis solution compositions and multiple peritoneal accesses were tried, and first accesses specifically for peritoneal dialysis were designed. In the 1950s and particularly 1960s new access features solved most of the problems and eliminated most complications of peritoneal dialysis performed in the supine position. The invention of silicone rubber catheter with polyester cuff(s) was a greatest breakthrough in peritoneal dialysis access development. Unfortunately, none of the currently used catheters is trouble free; poor dialysate drainage, pericatheter leaks, exit site and tunnel infections, and recurrent peritonitis episodes are frequently encountered. Therefore, there is an incessant search for new technological solutions, including new shapes of intraperitoneal and intramural catheter segments, and new catheter materials are tried.

Catheters, Indwelling↗
PubMed2006

History of peritoneal access development.

The first peritoneal accesses were devices that had been used in other fields (general surgery, urology, or gynecology): trocars, rubber catheters, and sump drains. In the period after World War II, numerous papers were published with various modifications of peritoneal dialysis. The majority of cases were treated with the continuous flow technique; rubber catheters for inflow and sump drains for outflow were commonly used. At the end of the 1940s, intermittent peritoneal dialysis started to be more frequently used. Severe complications of peritoneal accesses created incentive to design accesses specifically for peritoneal dialysis. The initial three, in the late 1940s, were modified sump drains; however, Ferris and Odel for the first time designed a soft, polyvinyl intraperitoneal tube with metal weights to keep the catheter tip in the pelvic gutter where the conditions for drain are the best. In the 1950s, intermittent peritoneal dialysis was established as the preferred technique; polyethylene and nylon catheters became commercially available and peritoneal dialysis was established as a valuable method for treatment of acute renal failure. The major breakthrough came in the 1960s. First of all, it was discovered that the silicone rubber was less irritating to the peritoneal membrane than other plastics. Then, it was found that polyester velour allowed an excellent tissue ingrowth creating a firm bond with the tissue. When a polyester cuff was glued to the catheter, it restricted catheter movement and created a closed tunnel between the integument and the peritoneal cavity. In 1968, Tenckhoff and Schechter combined these two features and designed a silicone rubber catheter with a polyester cuff for treatment of acute renal failure and two cuffs for treatment of chronic renal failure. This was the most important development in peritoneal access. Technological evolution never ends. Multiple attempts have been made to eliminate remaining complications of the Tenckhoff catheter such as exit/tunnel infection, external cuff extrusion, migration leading to obstruction, dialysate leaks, recurrent peritonitis, and infusion or pressure pain. New designs combined the best features of the previous ones or incorporated new elements. Not all attempts have been successful, but many have. To prevent catheter migration, Di Paolo and his colleagues applied the old idea of providing weights at the catheter tips to Tenckhoff catheters. In another modification, Twardowski and his collaborators created a permanent bend to the intra-tunnel portion of the silicone catheter to eliminate cuff extrusions. The Tenckhoff catheter continues to be widely used for chronic peritoneal dialysis, although its use is decreasing in favor of swan-neck catheters. Soft, silicone rubber instead of rigid tubing virtually eliminated such early complications as bowel perforation or massive bleeding. Other complications, such as obstruction, pericatheter leaks, and superficial cuff extrusions have been markedly reduced in recent years, particularly with the use of swan-neck catheters and insertion through the rectus muscle instead of the midline. However, these complications still occur, so new designs are being tried.

Animals↗
PubMed2006

Current trends in the use of peritoneal dialysis catheters.

The Tenckhoff catheter was developed in 1968 and has been widely used since for chronic peritoneal dialysis (PD) patients. Variations of the Tenckhoff catheter have been designed over the years in a search for the ideal PD catheter--an access that can provide reliable dialysate flow rates with few complications. Currently, data derived from randomized, controlled, multicenter trials dedicated to testing how catheter design and placement technique influence long-term catheter survival and function are scarce. As a result, no firm guidelines exist at the national or international levels on optimal PD catheter type or implantation technique. Also, no current statistics on the use of PD catheters are available. The last survey was carried out using an audience response system at the Annual Peritoneal Dialysis Conference in Orlando, Florida, in January 1994. The present analysis is based on a new survey done at the 2005 Annual Dialysis Conference in Tampa, Florida. It is a snapshot of preferences in catheter design and implantation technique in 2004 from an international sample of 65 respondent chronic PD centers. The Tenckhoff catheter remains the most widely used catheter, followed closely by the swan-neck catheter in both adult and pediatric respondent centers. Double-cuff catheters continue to be preferred over single-cuff catheters, and coiled intraperitoneal segments are generally preferred over straight intra-peritoneal segments. Surgical implantation technique remains the prevailing placement method in both pediatric and adult respondent centers.

Adult↗
PubMed2005

Rates of continuous ambulatory peritoneal dialysis-associated peritonitis at the University of Missouri.

Peritoneal dialysis (PD)-associated peritonitis contributes significantly to morbidity and modalityfailure. The number of patients on PD is declining in Western countries, and peritonitis is a potential deterrent to the therapy. Here, we present a clinically significant decline in the rate of peritonitis at a single center over a 28-year period, with current rates significantly lower than the national average, and we review several factors that have contributed to those outcomes. Peritonitis and duration of follow-up have been recorded for all patients followed in our program since 1977. Introduction of important technological changes into the program were also recorded. All peritonitis rates are expressed as episodes/patient-year or episodes/n patient-months. Data are summarized for each calendar year since 1977. We followed 682 patients for a total follow-up duration of 15,435 patient-months. Glass bottles were changed to plastic bags in 1978. Straight connecting tubes were replaced by Y-sets in 1988. The presternal dialysis catheter was introduced in 1991 and has been the primary PD access since 1995. The peritonitis rate in 1977 was 5.8 episodes/patient-year, and that rate has progressively declined over the past 27 years to 0.35 episodes/patient-year in 2004. Technical improvements that contributed to the decline in overall peritonitis rates have been adopted nationwide. The largest improvement occurred with the switch from glass bottles to plastic bags, and to the closed-system Y-set that incorporated the flush-before-fill principle. Advances in catheter technology have also played a key role. Quality improvement in the program and long years of experience in overall care of PD patients are significant factors that cannot be measured quantitatively. Improvements have been made to exit-site care protocols, to exit-site evaluation and diagnosis, and to treatment strategies. Patient education and training in catheter care remain the important factor in a PD program. Many factors have contributed to the reduction of PD-associated peritonitis rates at our center Improved connectology, catheter care, and patient education play key roles in the reduction of peritonitis.

Follow-Up Studies↗
PubMed2004

Early clinical, quality-of-life, and biochemical changes of "daily hemodialysis" (6 dialyses per week).

BACKGROUND: Advantages associated with an increased frequency of hemodialysis have been reported previously. However, previous studies were either small or not controlled and did not detail early clinical, biochemical, quality-of-life, urea kinetic, and dynamic changes when patients switched from a conventional (3 times/wk) dialysis regimen to "daily" (6 times/wk) dialysis therapy when total weekly dialysis time was unchanged. METHODS: A prospective sequential study with 21 patients as their own controls was performed. A 4-week period of conventional thrice-weekly dialysis (N = 240 treatments) was followed immediately by a 4-week period of daily (ie, 6 times/wk) dialysis (N = 480 treatments), in which each treatment was half the length of a conventional dialysis treatment session. Clinical parameters and symptoms during and between dialysis treatments were graded, and urea-related parameters, blood chemistry results, and nutritional data were determined. RESULTS: Within 4 weeks of switching to this daily dialysis regimen, there were improvements in blood pressure, dialysis "unphysiology," intradialytic and interdialytic symptoms, and urea kinetics and dynamics. There were fewer machine alarms and less need for nursing interventions during dialysis. Nutrition and quality of life began to improve. There was no increase in blood access complications and no significant changes in blood chemistry results, hematologic parameters, or use of medications. CONCLUSION: In this short-term study, daily dialysis appears to be a safe, better, and more physiological method to deliver dialysis care to patients with end-stage renal disease.

Adult↗
PubMed2003

Short peritoneal equilibration test: impact of preceding dwell time.

In the original peritoneal equilibration test (PET), which established standard values for membrane categorization in 1987, the dwell time of the preceding exchange was approximately 8 hours. Basing the test on an 8-hour prior exchange was convenient when almost all patients were on continuous ambulatory peritoneal dialysis (CAPD); however, many patients are now on some form of automated peritoneal dialysis (PD), and an 8-hour exchange before the PET requires a change in the dialysis schedule. Our goal in the present study was to determine whether the dialysate-to-plasma ratio (D/P) of solutes and the final dialysate to initial dialysate ratio (D/D0) of glucose in the short PET (2-hour equilibration time) are similar whether a 3-hour exchange or an 8-hour exchange precedes the test. The PETs were performed in 9 stable PD patients using 2 L of 2.5% dextrose dialysis solution (Baxter Healthcare, Deerfield, IL, U.S.A.). Before the equilibration exchange, the patients were on a randomly selected long (approximately 8-hour) or short (3-hour) dwell. During the equilibration exchange, dialysate samples were collected at 0.30, and 60 minutes of dwell time and from the drain bag (120-minute sample). Within a week, the PET was repeated in each patient after the alternate-length exchange. The values for D/P creatinine and urea and for D/D0 glucose were almost identical throughout the 2-hour PET after either the long or the short exchange. The D/P protein values tended to be higher in the PET after the long exchange. The short PET can be used for clinical purposes, and the creatinine and glucose results can be used for membrane categorization. Any dwell time between 3 and 12 hours is acceptable for the preceding exchange, and the equilibration test may be performed with either a 2-hour or a 4-hour dwell. The protein values obtained after a 3-hour prior dwell differ from those obtained after a long prior dwell. Protein values must therefore be standardized in a larger number of patients.

Creatinine↗
PubMed2002

Presternal peritoneal catheter.

The swan neck presternal catheter is composed of 2 flexible (silicon rubber) tubes joined by a titanium connector at the time of implantation. The exit site is located in the parasternal area. The catheter located on the chest was designed to reduce the incidence of exit site infections compared to peritoneal dialysis catheters with abdominal exits. From August 1991 to September 30, 2001, 974 swan neck presternal catheters were implanted worldwide. At the university of Missouri, 150 of these catheters were implanted and followed for over 130 patient years. Presternal catheters tended to perform better than swan neck abdominal catheters regarding exit and tunnel infections, even though they were implanted in several patients in whom regular catheters with the exit on the abdomen would be difficult or impossible to implant. Two-year survival probability of presternal catheters was 0.95. Recurrent/refractory peritonitis was the only reason for catheter failure. The catheter is particularly useful in obese patients (body mass index >35), patients with ostomies, children with diapers and fecal incontinence, and patients who want to take baths without the risk of exit contamination. Many patients prefer presternal catheter because of better body image. Disadvantages of the presternal catheter are minimal. Compared with abdominal catheters, dialysis-solution flow is slightly slower because of the increased catheter length; however, slower flow is insignificant clinically. There is a possibility of catheter disconnection in the tunnel, but this complication is extremely rare in adults and easily corrected. Finally, the implantation technique is more challenging compared with that of single-piece, abdominal catheters.

Catheters, Indwelling↗
PubMedDate not supplied

Blood access and daily hemodialysis: clinical experience and review of the literature.

The present authors studied longevity and complications with fistulae, grafts, and central venous catheters in 23 patients on daily hemodialysis for a total of 409 patient months (mean 18 +/- 10 months) and 9,209 dialyses. Fourteen patients had fistulae, five had grafts, and four had catheters. These required one, one, and two replacements respectively during a total observation time of 254, 105, and 50 patient months. Fistulae required 0.05 replacements per year vs. 0.11 replacements per year for grafts and 0.48 replacements per year for catheters (p = 0.042, fistulae vs. other accesses). Cumulative survival at 15 months was 100% for fistulae, 80% for grafts, and 20% for catheters, and at 3 years it was 80% for fistulae and grafts. No catheter survived beyond 15 months (p = 0.041). Twenty-seven events required hospitalization or an outpatient intervention. Fistulae had 0.52 events per patient year, grafts 1.37 events per patient year, and catheters 1.44 events per patient year (p = 0.080, fistulae vs. other accesses). Patients with fistulae reported more problems between dialyses, these occurring on 3.2% of the observation days compared with 0.2% for grafts and 0.4% for catheters (p < 0.0001). Eighty-five percent of these problems were pain and redness at the access site. During dialysis, there were more problems with catheters (9.1% vs. fistulae 2.7% and grafts 0.9%, p < 0.0001). Complications and survival data were similar to those reported with daily hemodialysis by others and better than data from reports of access problems with conventional three times weekly hemodialysis. In conclusion, daily hemodialysis does not adversely affect the usual types of blood access. Survival was best and need for intervention was least with fistulae and worst with catheters. Grafts, when functioning, had fewer problems both between and during dialyses.

Adult↗
PubMedDate not supplied

The Aksys personal hemodialysis system.

The Aksys personal hemodialysis system empowers patients to dialyze where, when, and how they want. It allows them to easily do the best dialysis--daily hemodialysis--in the safest place--at home--by simplifying operation (almost anyone can do it), doing the drudgery work of dialysis (the patient is the master, not the slave of the dialysis machine, giving patients their lives back), needing no bulky disposables (patients have their homes back), reducing emergencies during dialysis, and performing immediate fluid resuscitation on demand.

Clinical Trials as Topic↗
PubMedDate not supplied

Dialyzer reuse-Part I: Historical perspective.

The first apparatus for hemodialysis in animals, made painstakingly by Abel et al. in their laboratory at the beginning of 20th century, was cleaned with acid-pepsin to digest blood, disinfected with thymol, and reused for up to 30 experiments for as long as 8 months. The obvious incentive was saving time. In the early years of hemodialysis in patients, dialyzers and lines were assembled and sterilized immediately before dialysis. Various methods of dry and moist heat sterilization and miscellaneous chemical agents were employed for disinfection. Significant time was required to assemble the dialyzers, so there was an incentive to reuse previously assembled dialyzers to save time, especially for home hemodialysis. Bleach to clean and formaldehyde to disinfect the membranes and lines was used for this purpose. Preassembled dialyzers, commercially introduced in the 1950s, were the most expensive components of hemodialysis systems, therefore reprocessing of these dialyzers was the most effective way to save money. Refrigeration of coil dialyzers with blood, introduced in the mid-1960s, was associated with frequent febrile reactions and was soon abandoned. Preassembled coil and plate dialyzers permitted almost complete return of blood after dialysis and led to the introduction of chemical disinfection for dialyzer reprocessing. A variety of disinfectants have been used. Formaldehyde was the most common disinfectant until the end of the 1970s. Sodium hypochlorite was used to clean the majority of dialyzers and to sterilize dialyzers with polyacrylonitrile membranes. In the early 1980s, peracetic acid and glutaraldehyde started to compete with formaldehyde. By the 1990s, formaldehyde had become less popular than peracetic acid. In the mid-1990s, disinfection and membrane cleaning with acetic acid and heat was introduced. Manual reprocessing was replaced by early reuse machines in the mid-1970s and a more sophisticated second generation of automated hemodialyzer reprocessing machines followed in the late 1970s. Recently disinfection of dialyzers with moist heat has resumed. Saving both time for the patient and money for the provider were the main motivations for designing a new machine for daily home hemodialysis. The machine, developed in the 1990s, cleans and moist-heat disinfects the dialyzer and lines in situ so they do not need to be changed for a month. In contrast, the reuse of dialyzers in home hemodialysis patients treated with other hemodialysis machines has become less popular and is almost extinct.

Disinfectants↗
PubMedDate not supplied

Dialyzer reuse--part II: advantages and disadvantages.

Although single dialyzer use and reuse by chemical reprocessing are both associated with some complications, there is no definitive advantage to either in this respect. Some complications occur mainly at the first use of a dialyzer: a new cellophane or cuprophane membrane may activate the complement system, or a noxious agent may be introduced to the dialyzer during production or generated during storage. These agents may not be completely removed during the routine rinsing procedure. The reuse of dialyzers is associated with environmental contamination, allergic reactions, residual chemical infusion (rebound release), inadequate concentration of disinfectants, and pyrogen reactions. Bleach used during reprocessing causes a progressive increase in dialyzer permeability to larger molecules, including albumin. Reprocessing methods without the use of bleach are associated with progressive decreases in membrane permeability, particularly to larger molecules. Most comparative studies have not shown differences in mortality between centers reusing and those not reusing dialyzers, however, the largest cluster of dialysis-related deaths occurred with single-use dialyzers due to the presence of perfluorohydrocarbon introduced during the manufacturing process and not completely removed during preparation of the dialyzers before the dialysis procedure. The cost savings associated with reuse is substantial, especially with more expensive, high-flux synthetic membrane dialyzers. With reuse, some dialysis centers can afford to utilize more efficient dialyzers that are more expensive; consequently they provide a higher dose of dialysis and reduce mortality. Some studies have shown minimally higher morbidity with chemical reuse, depending on the method. Waste disposal is definitely decreased with the reuse of dialyzers, thus environmental impacts are lessened, particularly if reprocessing is done by heat disinfection. It is safe to predict that dialyzer reuse in dialysis centers will continue because it also saves money for the providers. Saving both time for the patient and money for the provider were the main motivations to design a new machine for daily home hemodialysis. The machine, developed in the 1990s, cleans and heat disinfects the dialyzer and lines in situ so they do not need to be changed for a month. In contrast, reuse of dialyzers in home hemodialysis patients treated with other hemodialysis machines is becoming less popular and is almost extinct.

Anaphylaxis↗