Chronic peritoneal dialysis catheters: challenges and design solutions.

Although highly successful as transcutaneous access devices, today's peritoneal dialysis catheters still have imperfect hydraulic function, biocompatibility and resistance to infection. Success of Tenckhoff catheters is greatly improved by the proper positioning of deep and subcutaneous cuffs and intraperitoneal segment. Newer peritoneal catheter designs are intended to improve hydraulic function, avoid outflow failure, and diminish exit site infection. These catheter designs serve as excellent alternatives for patients with various types of failure of Tenckhoff catheters. Catheters have been designed for Continuous Flow Peritoneal Dialysis, and have generally been successful in providing high peritoneal dialysis flow rate, but not always successful in optimally distributing flow of peritoneal fluid. Improvements in catheter design may expand the use of peritoneal dialysis as a successful home dialysis therapy.

Assessment of biomaterials as components of a reciprocating dialyser during canine dialysis.

A recently reported device, the sorbent suspension reciprocating dialyser (SSRD), was investigated for use as a test system for biocompatibility of dialyser components. The device is easy to assemble and operate, and allows minimal blood contact with foreign material outside of dialyser components. Its constant pressure/variable flow rate operation allows quantification of degree of clotting of dialyser versus time. The effect of heparinization of the blood distribution gaskets (BDG) of the device on performance and dialyser lifetime was investigated. Heparin was bound to the surface of polyethylene gaskets by immersion in a solution of tridodecylmethylammonium chloride (TDMAC)--heparin complex for several hours. Gaskets were then assembled in an SSRD which was then used for experimental dialysis in dogs with AV shunts. Dialysers assembled using non-heparinized gaskets were used as controls. Blood coagulation tendency was quantified by the activated clotting time (ACT) and partial thromboplastin time (PTT), and these values correlated with the rate of clotting of the device. Heparinization of the gaskets resulted in the prevention of clotting in the dialyser until the final minutes of dialysis in all cases, in contrast to the constant decay of blood fill volume and evidence of clotting in the non-heparinized cases. However, dialyser lifetime was not significantly increased by gasket heparinization. At normal initial values of ACT (80-95 s) dialyser clotting occurred in 10-15 min. In tests with non-heparinized gaskets and systemically heparinized dogs, values obtained in the ACT test were observed to decrease during dialysis, indicating the disappearance of heparin from the blood. Both ACT and PTT tests show promise as predictors of dialyser lifetime.

Roux-Y intestinal bypass for administration of sorbents in uremia.

In order to minimize interaction of sorbents with food and digestive secretions, an intestinal bypass was created for sorbent administration in normal and uremic rats (N = 18) and goats (N = 5). Two separate limbs of small intestine were fashioned, one for food absorption and one for sorbent function, which joined at a Roux-Y anastomosis before the cecum. Particulate sorbent suspensions were injected into the intestine via a cutaneous stoma, and were excreted with food wastes in the feces. In animals with normal kidneys, sorbent function was calculated from changes in fecal and urinary excretion. Nitrogen clearance by the intestinal bypass was 20 to 40% of normal renal clearance in rats and goats. Potassium clearance was 40% of normal renal clearance in rats, and over 100% in goats. Sorbent treatment in anephric animals caused serum urea nitrogen concentrations to stabilize at 210 mg/dl in rats, and 110 mg/dl in goats. Serum potassium concentrations stabilized at 4.5 mEq/liter in rats, and fell to 2 mEq/liter in goats. Water balance was maintained by producing a mild osmotic diarrhea. At least three substances which accumulate in renal failure--urea, potassium, and water--were removed in therapeutically significant amounts.

Evaluation of the sorbent suspension reciprocating dialyser in the treatment of overdose of paracetamol and phenobarbitone.

Poisoning with paracetamol (acetaminophen) and phenobarbitone is a common occurrence in the United States and Europe. The removal efficiency of these drugs by a sorbent suspension reciprocating dialyser (SSRD) has been investigated. The SSRD is a parallel plate dialyser with a reciprocating blood flow and free mobile sorbent suspension composed of charcoal and zeolites. This arrangement provided a system with minimal sorbent saturation. High performance liquid chromatography was used for the quantification of the drugs in aqueous and serum fluids. The in-vitro removal efficiency of the dialyser was studied by dialysing a large volume of the drug in solution for 12 to 16 h. The removal efficiency remained relatively constant up to 10 h of dialysis. The in-vivo dialysis studies were performed using normal dogs. Large doses of the drugs were administered orally or intravenously to achieve high blood levels. The clearance values obtained from these studies were comparable with, or in excess of, the values reported in the literature for conventional dialysers. The major advantage of the SSRD is the ability of the unit to be used for prolonged dialysis and to provide a system with minimal sorbent saturation due to mixing and interchange of sorbent granules next to the membrane surface.

Continuous flow-through peritoneal dialysis (CFPD): comparison of efficiency to IPD, TPD, and CAPD in an animal model.

OBJECTIVE: To determine whether continuous flow-through peritoneal dialysis (CFPD), a treatment schedule in which peritoneal dialysate is infused continuously into one part of the abdomen (over the liver) and is drained from a distant part of the abdomen (the pelvis), can provide greater clearance than continuous ambulatory peritoneal dialysis (CAPD), tidal peritoneal dialysis (TPD), or intermittent peritoneal dialysis (IPD). DESIGN: A prospective study comparing four schedules of peritoneal dialysis in the awake, normal dog, using glucose clearance as a substitute for urea clearance. METHODS: We placed two chronic dialysis catheters into the abdomen of anesthetized dogs (with intraperitoneal portions of fluted or miniature column-disc design). On successive days, with the dogs awake and prone, we performed peritoneal dialysis for 4 hours with 1.5% dialysate according to one of four schedules, each with 2 L maximum intraperitoneal volume: CFPD (unidirectional flow at an average of 3.6 L/hr), IPD (2 L/hr), TPD (average of 3.6 L/hr, 1 L residual volume), and CAPD (2 L/4 hr). Glucose and urea clearances were calculated from blood and peritoneal concentrations and dialysate flow rates. RESULTS: Stabilized glucose clearances (from 60 to 240 minutes) averaged 11 +/- 5 mL/min for IPD, TPD, and CFPD, and 5 +/- 2 mL/min for CAPD. However, glucose clearances of CFPD were 13 +/- 6 mL/min when the intraperitoneal volume was maintained at 800-100 mL, and 16.5 +/- 6 mL/min when flow rate was 6 L/hr. Urea clearances were twice the measured glucose clearances. CONCLUSION: When CFPD is performed with an appropriate intraperitoneal volume and flow, it is the most chemically effective method of peritoneal dialysis in removing small molecules like urea.

Peritoneal catheters and exit-site practices: toward optimum peritoneal access.

The peritoneal catheter is the CAPD patient's lifeline. Advances in catheter knowledge have made it possible to access the peritoneal cavity safely and maintain access over an extended period of time. Infection at the exit site remains a major problem, a solution for which is being extensively researched. The successful outcome of a catheter in an individual depends on meticulous care and adherence to sound principles of catheter insertion and management. The guidelines provided in this publication represent the consensus based on the extensive experience of several major centers worldwide.

Innovative peritoneal dialysis: flow-thru and dialysate regeneration.

As the peritoneal dialysis (PD) patient's residual renal function declines, the dialysis dose must be increased. However, the options for increasing the dose are limited to increasing the number of exchanges and/or the volume of each exchange. A review of the literature indicates that the dialysis dose can be significantly increased by flow-through PD, wherein the dialysate flows continuously into the peritoneal cavity through one catheter and out another and/or by regenerating the spent dialysate, thereby, significantly increasing the dialysate flow rate. Flow-thru PD has been used with and without dialysate regeneration. Regeneration has been used with standard inflow/outflow PD. In nearly all cases, substantially increased clearances over standard PD were obtained with reported urea and creatinine clearances as high as 58 and 48 ml/min, respectively. Applying flow-thru to the PD patient would require two catheters or a dual lumen catheter, and to obtain optimum clearances, the dialysate should be pumped through the peritoneal cavity at a high flow rate. Regenerating the dialysate allows high dialysate flow rates while reducing the total amount of dialysate required. For the continuous ambulatory peritoneal dialysis (CAPD) patient, the unit would have to be wearable; whereas for the patient on automated PD, flow-thru and/or regeneration PD could be incorporated into the equipment. With sorbent regeneration, the protein in the spent PD could be purified and returned to the patient thereby minimizing protein loss, increasing ultrafiltration, and enhancing the removal of protein-bound metabolic toxins.

Comparison of blood flow rates and hydraulic resistance between the Mahurkar catheter, the Tesio twin catheter, and the Ash Split Cath.

The Ash Split Cath (Medcomp, Harleysville, PA) is a recently introduced dual lumen permanent catheter designed to be placed through the internal jugular vein into the superior vena cava by single venipuncture technique. The transcutaneous portion is a 14 French cylindrically shaped catheter with D-shaped lumens and a Dacron (DuPont, Wilmington, DE) cuff. At the entrance to the jugular vein, the catheter splits into two separate D-shaped limbs that then merge into multiholed cylindrical tips in the vena cava. Split Caths (n = 10) have been placed in patients with end-stage renal disease and used for outpatient dialysis for approximately 2 months. Flow rates and hydraulic resistance have been compared with Mahurkar (Bard, Salt Lake City, UT) (n = 22) and Tesio (Medcomp) (n = 17) catheters in the same unit. Average blood flow rates (Qb) were 295 +/- 42 (SD) for Ash Split Caths vs 279 +/- 38 and 300 +/- 39 ml3/min for Mahurkar and Tesio catheters, respectively, and hydraulic resistances were 0.44 +/- 0.17, 0.52 +/- 0.15, and 0.56 +/- 0.11 mmHg/ml/min, respectively (not significant). No Split Caths have been removed for bleeding or flow complications. The Split Cath provides the simplicity of placement and removal of a single-bodied catheter with flow advantages of independent, cylindrical, multiholed tips.

Systemic inflammatory response syndrome treatment by powdered sorbent pheresis: the BioLogic-Detoxification Plasma Filtration System.

Systemic inflammatory response syndrome (SIRS) is one of the most common causes of death in intensive care unit patients. The detoxification plasma filtration (DTPF) system (HemoCleanse, Inc., West Lafayette, IN) combines the DT hemodiabsorption system in series with a push-pull pheresis PF system (a suspension of powdered sorbents surrounding 0.5 microm plasma filter membranes). Bidirectional plasma flow (at 80-100 ml/min) across the PF membranes provides direct contact between plasma proteins and powdered sorbents, as well as clearance of cytokines (tumor necrosis factor-alpha, interleukin-1beta, and interleukin-6) at a rate of 15-25 ml/min, without evidence of saturation for 90 minutes. In a U.S. Food and Drug Administration approved study we treated eight patients with SIRS and organ failure with a single DTPF treatment, using powdered charcoal as sorbent in four patients and powdered charcoal and silica in four patients. Treatments proceeded for 6 hours with proper heparin anticoagulation (activated clotting time 250-300 sec) and appeared safe. All patients improved during the treatments and each had increased blood pressure and decreased need for pressor agents. Plasma cytokine levels stabilized or decreased during treatment and were significantly lower the morning after treatment. Multiple organ dysfunction (MOD) and Acute Physiology Chronic Health Evaluation II scores and organ function gradually improved in most patients, and two patients survived for more than 28 days and two for more than 14 days. The DTPF System may prove beneficial in treatment of patients with sepsis.

Push-pull sorbent based pheresis for treatment of acute hepatic failure: the BioLogic-detoxifier/plasma filter System.

The BioLogic-DT (detoxifier) System is an extracorporeal blood treatment device that uses the membranes of a cellulosic plate dialyzer to propel blood in and out through a single lumen access (on a 12 sec cycle) and circulates a suspension of powdered charcoal and cation exchanger through the dialysate spaces to absorb many soluble toxins in the treatment of hepatic failure. The BioLogic-DTPF (detoxifier/plasma filter) System adds two Gambro plasma filters downstream from the plate dialyzer, which allows most of the blood plasma to pass out of the blood, contact powdered charcoal in a suspension, and then return to the blood during each 12 sec cycle (creating push-pull sorbent based pheresis). A roller pump exchanges charcoal suspension between the plasma filter case and a 700 ml bag of powdered charcoal suspension. At a blood flow rate of 150-200 ml/min, 100 ml/min of plasma moves bidirectionally through the plasma filter membranes. Direct contact of plasma with charcoal outside the plasma filter membranes removes creatinine with a clearance rate equal to plasma flow (100 ml/min); clearance of strongly protein bound toxins, such as unconjugated bilirubin, is lower (10-40 ml/min). In this article, the authors explain the mechanisms of operation of this system and present in vitro tests that define its chemical efficiency. Also described are potential problems, tests that indicate the severity of these problems, and monitors and algorithms to detect or avoid these problems in clinical use of the system. The results of the treatment of two patients with acute hepatic failure and coma using the BioLogic-DTPF System are reviewed.

A subcutaneous capillary filtrate collector for measurement of blood chemistries.

The capillary filtrate collector (CFC) contains 30,000 molecular weight cut-off, hollow fiber ultrafiltration membranes that are placed below the skin. A transcutaneous tube leads to an evacuated glass tube that provides a vacuum to pull ultrafiltrate at 40-60 microliters/hr from blood, through the fibers, and past a sampling port to the glass tube. Long-term (1-6 months) animal and clinical studies have shown that the ultrafiltrate concentration of chemicals such as glucose and a variety of drugs is exactly the same as that of the blood plasma water when the ultrafiltrate is created. In this study, the device was placed in six home monitored diabetics and four in-center hemodialysis diabetic patients. Over the following month, blood glucose concentrations were compared to CFC glucose concentrations. In spite of difficulties in diluting and assaying small samples of filtrate, there was a good correlation between blood and CFC glucose levels. A flow-through enzymatic glucose sensor has been tested and shown to accurately measure glucose in CFC filtrate. When placed in the transcutaneous tubing near the skin, this should allow a small external device to continuously monitor glucose levels in brittle or out of control diabetes with high accuracy and little risk, discomfort, or cost.

Effect of sorbent-based dialytic therapy with the BioLogic-DT on an experimental model of hepatic failure.

An experimental model of hepatic failure in the dog has been developed in which the liver is devascularized in two stages. Under general anesthesia, a portacaval shunt is created, ligatures placed around the hepatic and gastroduodenal arteries, and the dog recovered. Two days later under general anesthesia, the ligatures are pulled, converting hepatic insufficiency to hepatic failure. Five control animals developed hypotension, severe lactic acidosis, hypoglycemia, and increasing liver enzyme levels during 6 hrs of follow-up. The BioLogic-DT system includes a cellulosic plate dialyzer with a suspension of powdered charcoal and cation exchangers as dialysate. Five animals were treated with the BioLogic-DT for 6 hrs after creation of hepatic failure. These animals were more stable physiologically, developed less lactic acidosis and less enzyme elevation, and maintained high normal blood glucose levels. The results help explain the clinical improvement demonstrated in patients with hepatic failure treated by the BioLogic-DT, and confirm that many of the toxins of hepatic failure are dialyzable and bound by simple sorbents such as charcoal and cation exchangers.

Subcutaneous capillary filtrate collector for measurement of blood glucose.

The capillary filtrate collector (CFC) is a device that creates an ultrafiltrate at 50-100 microliters/h from subcutaneous capillaries, and carries this filtrate out of the body for chemical analysis. From inside out, components include three looped hollow fiber ultrafiltration membranes, a polytetrafluoroethylene (PTFE) cuff, polyurethane tubing, a "Y" connector leading to a sampling port, a hub, and a needle placed into a 5 ml vacutainer tube. Animal studies have demonstrated that the CFC filtrate glucose level is exactly that of blood at the time the filtrate is created. The authors have performed clinical trials to determine the correlation of blood glucose and CFC glucose levels, and the time delay between contemporary samples. Seven diabetic patients wore the CFC device, tubing, and vacutainer tube for 1 month. In home monitored diabetic patients, fingerstick glucose measurements were performed at the usual daily schedule. The vacutainer was then evacuated, and this average sample analyzed and compared with the average of prior blood glucose levels. An optical device then was applied to measure the linear velocity of CFC fluid through external tubing, and predict the time for fluid to pass from fibers to the sampling port (average, 25 min). Capillary filtrate collector samples drawn at this time had glucose concentrations that generally correlated with blood levels. In diabetic patients on hemodialysis, the vacutainer was evacuated at the start of each treatment, and CFC and blood samples were drawn every 20 min during the treatment. Comparison of glucose-versus-time curves indicated a reasonable correlation between blood and CFC samples, with a delay related to flow rate (which declined 50% during dialysis).(ABSTRACT TRUNCATED AT 250 WORDS)

Extracorporeal whole body hyperthermia treatments for HIV infection and AIDS.

Whole body hyperthermia therapy (WBHT) is the elevation of the core body temperature to 42 degrees C. In vitro studies have confirmed that 42 degrees C is cytocidal for virally infected lymphocytes, and even more effective when heating is repeated 4 days later. The safety and efficacy of two successive sessions of WBHT (4 days apart) was evaluated in 30 patients with AIDS (not on protease inhibitors), randomized to: 1) untreated controls, 2) low temperature WBHT for 1 hour at 40 degrees C and repeated 96 hours later, and 3) high temperature WBHT for 1 hour at 42 degrees C and repeated 96 hours later. The sorbent suspension in the ThermoChem System (HemoCleanse, West Lafayette, IN) system automatically controlled blood phosphate, calcium, and other electrolyte concentrations during WBHT. In 1 year of follow-up after WBHT, there were positive effects of the therapy on frequency of AIDS defining events, Karnofsky score, and weight maintenance. However, effects on plasma HIV RNA and CD4 counts were transient. Two successive WBHT treatments were performed in four patients who were on protease inhibitor/triple drug therapy, but had suboptimal response. In follow-up for 6 months, plasma HIV RNA and CD4 improved after WBHT, and the patients remained clinically well. This WBHT may have specific advantages in patients with suboptimal response to protease inhibitor therapy.

Effect of hemodiabsorption and sorbent-based pheresis on amino acid levels in hepatic failure.

Changes in plasma amino acid concentrations were measured in patients with hepatic failure during extracorporeal hemodiabsorption (using the Liver Dialysis Unit, "the Unit") or hemodiabsorption plus sorbent-based pheresis treatment (using the Liver Dialysis Plasmafilter Unit, "the PF-Unit") Systems. Eight patients with hepatic failure, grade 3 or 4 encephalopathy, elevated bilirubin and/or creatinine levels and respiratory or renal failure were treated for 1-3 days with the Unit alone. Three of these were also treated with the Unit containing 10 g of BCAA in the sorbent suspension. Four patients with hepatic failure treated with the PF Unit also had 10 g of branched chain amino acid (BCAA) added to the sorbents of the Unit portion of this device. Pre- and post-plasma samples were drawn and high performance liquid chromatography (HPLC) was used to separate and detect amino acids in the plasma. Both the Unit and the PF-Unit have the capability to selectively remove various amino acids, especially aromatic amino acids (AAA). The pre-treatment amino acid profiles of plasma were typical for hepatic failure, with abnormally high levels of phenylalanine, tyrosine, tryptophan, and methionine and decreased levels of valine, leucine and isbolucine. The average pre-treatment Fischer ratio (BCAA/AAA) for both Unit and PF-Unit patients was 1.43 (+/- 0.58). Treatments by both systems resulted in an increase of BCAA levels in blood and concomitant decrease of AAA levels, with an average Fischer ratio improvement of 30-38% for the Unit and PF-Unit without BCAA. The Fischer ratio improved by 90% (average) for the Unit with BCAA. Levels of many other amino acids (such as alanine, glycine, proline or lysine) increased during both Unit and PF-Unit treatments. The removal of strongly protein-bound toxin and amino acids such as tryptophan and sulphydryl amino acids was more effective by the PF-Unit. Both the Unit and the PF-Unit have the unique capability to remove toxic aromatic amino acids while increasing BCAA levels in patient. The increase in many amino acid levels may be related to the removal of toxins that interfere with normal amino acid metabolism. The addition of the PF module improves the removal of bilirubin and similarly protein-bound chemicals. Changes in amino acid profiles by the Unit and the PF-Unit contrast markedly with other extracorporeal devices.

Effect of ethanol perfusion on creatinine removal in a Roux-Y intestinal segment.

Five rats and 2 goats had a bypass operation to allow infusion of sorbents through an inlet ostomy. The sorbents passed through one limb of intestine isolated from food contact to join a food limb which included 30-40% of the original length of small intestine. In goats, serum creatinine levels were elevated by infusion of sterile creatinine solutions intravenously. Twenty-four hour urines were collected before, during and after periods of infusion of sorbents into the inlet ostomy. Infusion of charcoal into the ostomy had little effect on the total daily urinary creatinine excretion (TDUC). However infusion of 4.3 g/kg/day ethanol decreased the TDUC significantly, in both species. In rats, 8.6 g/kg/day ethanol infusion had an even greater effect on TDUC. Studies of intraluminal creatinine concentration in the distal part of the sorbent segment indicated that especially when serum concentration of creatinine is over 2 mg%, ethanol greatly increases the intraluminal creatinine concentration in the intestine. It is concluded that ethanol, in combination with intestinal sorbents or alone, could allow intestinal dialysis to remove considerably more creatinine, and possibly aid transport of other organic substances.

Clinical effects of a sorbent suspension dialysis system in treatment of hepatic coma (the BioLogic-DT).

Fifteen patients with acute deterioration of liver function, high serum ammonium, and an average coma level of 3.9 were identified. Eleven of the patients were on respirator support, and eleven had kidney failure pursuant to the liver failure. The patients were treated for 8-12 hours daily with the BioLogic-DT system, in which membranes of a cellulosic plate dialyzer actively pump blood through a single access at over 200 ml/min, and the dialysate contains a suspension of powdered activated charcoal (300,000 square meters surface area) and cation exchanger (160 meq capacity). No anticoagulant was used. In spite of the declining condition of the patients prior to treatment, there was a statistically significant improvement in neurologic status during individual treatments, and a positive trend over 1-12 (average four) daily treatments. Four patients recovered liver function and another four improved enough to receive a liver transplant operation. The BioLogic-DT system appears to be safe in treatment of patients with hepatic insufficiency and coma. The neurologic improvement of these patients indicates that many toxins of hepatic failure are dialyzable across cellulosic membranes and bound by charcoal.

Push-pull sorbent-based pheresis treatment in an experimental canine endotoxemia model: preliminary report.

The Biologic-DTPF System (DTPF), an extracorporeal blood treatment device with potential to treat sepsis, was tested in a preliminary study using a canine endotoxemia model. Six dogs were used and they formed four treatment groups, as control group (n=1) and three groups based on the type of sorbent present in the plasma filter (PF) system: sham treatment with no sorbent (n=1), charcoal as sorbent (n=2), and charcoal/silica as sorbent ("silica" group, n=2). Cardiodynamic data were recorded before treatment and every 30 minutes, and blood samples were collected to determine blood chemistry and to detect the levels of endotoxin and selected plasma cytokines: interleukin-1 (IL-1), interleukin-6 (IL-6), and tumor necrosis factor (TNF). The dogs were given Escherichia coli endotoxin (2 mg/kg) as an intravenous drip (extended over a period of 30 minutes). Thirty minutes after the end of infusion all animals except the control were treated with the DTPF system for four hours. To determine the effect of treatment, data collected at one hour from the initiation of treatment until the end of treatment were compared between control and treated dogs. The endotoxin levels in the control dog were higher (P < 0.05) than other groups. The control dog had lower levels of TNF than other groups. The control dog had similar levels of IL-1 (P > 0.05) and higher levels (P < 0.05) at 4 hours into treatment compared to other groups. The control dog had similar levels of IL-6 as other groups (P > 0.05). In the control dog, the mean arterial pressure (MAP) fell and then remained low but stable at 1-4 hours. The charcoal group had lower MAP than the control dog at 1-4 hours (P < 0.05). The silica group had higher MAP levels similar to the control dog. After treatment, the control dog had higher (P < 0.05) values of hematocrit, hemoglobin, calcium, potassium, and albumin compared to the treated groups. As expected for a system removing plasma during sepsis, the DTPF System had some adverse effects on the physiologic status of the dogs, especially when loaded with charcoal sorbent only. The findings of the present study suggest that the filters are capable of eliminating endotoxin and there is some evidence of cytokine removal. Although the charcoal dogs did poorly, addition of silica to the sorbent offset any negative effects. Further work is underway to improve the efficiency of the system, primarily to enhance the capacity of the sorbents for cytokines. A more realistic canine sepsis model with mortality after several days (the Escherichia coli- infected intraperitoneal clot) will also be considered in future studies.

Bedside peritoneoscopic peritoneal catheter placement of Tenckhoff and newer peritoneal catheters.

The success of Tenckhoff chronic peritoneal dialysis catheters depends more upon the skill of the physician in placing catheters and on the technique of placement than it does on the exact design of the peritoneal catheter. In this summary article, the existing types of peritoneal catheters are reviewed, including two recent alternative designs: Tenckhoff catheters with larger internal diameters, and the T-fluted catheter with grooved limbs adjacent to the parietal peritoneum. The three types of placement procedures for catheters (peritoneoscopy, surgical or dissective, and blind techniques) are described, and the complications of Tenckhoff catheters are compared according to placement technique.

T-fluted peritoneal dialysis catheter.

While the current Tenckhoff catheter is generally successful, outflow failure due to omental obstruction, pericatheter hernias, pericatheter leaks, and exit infections remains a major cause for dropout from peritoneal dialysis therapy. Further, the irregular outflow characteristics of the catheter make highflow automated dialysis problematic. We have developed a catheter with a thin transabdominal tube connecting in a T-shape to a transverse cylinder resting against the parietal peritoneum, with flutes (grooves) as ports. The catheter can be inserted through the 3-mm diameter Quill guide of the Y-TEC peritoneoscopic system. Studies in normal dogs indicated that the T-fluted catheter allowed daily exchanges with 2 L of peritoneal dialysate without outflow obstruction, and peritoneoscopic inspection 2-4 weeks later showed no omental attachment to the grooved ports. By comparison, curled Tenckhoff catheters uniformly developed omental obstruction within 2-4 days, and all such catheters had firm omental attachment to the side holes. Five T-fluted catheters have been placed in continuous ambulatory peritoneal dialysis (CAPD) patients who had prior complications with Tenckhoff catheters (infections, leaks, and outflow failure). One patient with multiple intraperitoneal adhesions developed outflow failure of the T-fluted catheter, similar to a prior Tenckhoff catheter. All other T-fluted catheters had consistent outflow rates and no complications. In long-term use the T-fluted catheter should prevent omental attachment, deep cuff extrusion, pericatheter hernias, subcutaneous cuff erosion, and exit-site infection, although this is not yet proven.