Continuous flow peritoneal dialysis: principles and applications

Impact of Glucose in Peritoneal Dialysis: Saint or Sinner?

Peritoneal dialysis (PD) solutions using glucose as osmotic agent have been used for more than two decades as effective treatment for patients with end-stage renal disease. Although alternative osmotic agents such as amino acids and macromolecular solutions, including polypeptides and glucose polymers, are now available, glucose is still the most widely used osmotic agent in PD. It has been shown to be safe, effective, readily metabolized, and inexpensive. On the other hand, it is widely assumed that exposure of the peritoneal membrane to high glucose concentrations contributes to both structural and functional changes in the dialyzed peritoneal membrane. As in diabetes, glucose, either directly or indirectly through the generation of glucose degradation products or the formation of advanced glycation end products, may contribute to peritoneal membrane failure. Although efforts to reduce glucose toxicity have been made for years, only a few suggestions, such as dual-bag systems with bicarbonate as buffer system, have found broader acceptance. Recently, some interesting new approaches to the problem of glucose-related toxicity have been made, but further investigations will be necessary before they can be used clinically. This review will focus on adverse effects of glucose in PD solutions and summarize different aspects of glucotoxicity and potential therapeutic interventions.

Urgent start peritoneal dialysis

PURPOSE OF REVIEW

Although historically peritoneal dialysis was widely used in nephrology, it has been underutilized in recent years. In this review, we present several key opportunities and strategies for revitalization of urgent start peritoneal dialysis use, and discuss the recent literature on clinical experience with peritoneal dialysis use in the acute and unplanned setting.

RECENT FINDINGS

Interest in using urgent start peritoneal dialysis to manage acute kidney injury (AKI) and unplanned chronic kidney disease (CKD) stage 5 patients has been increasing. To overcome some of the classic limitations of peritoneal dialysis use in AKI, such as a high chance of infectious and mechanical complications, and no control of urea, the use of cycles, flexible catheters, and a high volume of dialysis fluid has been proposed. This knowledge can be used in the case of an unplanned start on chronic peritoneal dialysis, and may be a tool to increase the peritoneal dialysis penetration rate among incident patients starting chronic dialysis therapy.

SUMMARY

Peritoneal dialysis should be offered in an unbiased way to all patients starting unplanned dialysis, and without contraindications to peritoneal dialysis. It may be a feasible, well tolerated, and complementary alternative to hemodialysis, not only in the chronic setting, but also in the acute.

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.

Developments in extracorporeal therapy for the poisoned patient

The modern use of extracorporeal therapies to treat poisoning and drug overdoses dates back to the early 20th century and has evolved along with their use as treatment for acute kidney injury or as maintenance therapy in advanced kidney disease. As our understanding of drug pharmacokinetics and membrane materials has increased, the technologies of extracorporeal therapy and their applications have become more sophisticated. Despite that, there is little robust evidence to guide clinicians on the optimal use of extracorporeal therapy in treating poisoning beyond case reports and series. New efforts are underway to remedy that: the Extracorporeal Treatments in Poisoning Workgroup (EXTRIP) is an international effort on the part of nephrologists, pharmacists and toxicologists to review the available data and formulate evidence-based guidelines on how to use extracorporeal techniques to treat poisoning and improve patient outcomes. Meanwhile, new techniques and membranes are under development. This review will summarize those key scientific and technologic developments, the efforts to optimize their use and new directions in research.

Available extracorporeal treatments for poisoning: overview and limitations

Poisoning is a significant public health problem. In severe cases, extracorporeal treatments (ECTRs) may be required to prevent or reverse major toxicity. Available ECTRs include intermittent hemodialysis, sustained low-efficiency dialysis, intermittent hemofiltration and hemodiafiltration, continuous renal replacement therapy, hemoperfusion, therapeutic plasma exchange, exchange transfusion, peritoneal dialysis, albumin dialysis, cerebrospinal fluid exchange, and extracorporeal life support. The aim of this article was to provide an overview of the technical aspects, as well as the potential indications and limitations of the different ECTRs used for poisoned patients.

Approach to the Metabolic Implications of Peritoneal Dialysis in Acute Kidney Injury

During the 1970s and 1980s, peritoneal dialysis (PD) was widely accepted as the standard treatment for acute kidney injury (AKI). However, advances in the techniques of extracorporeal blood purification gradually reduced its use, making PD an underused modality in this context. Although PD for AKI is an underutilized modality worldwide, it is frequently used in developing countries because of its lower cost and minimal infrastructure requirements. Recent studies have shown that PD administered continuously through a flexible catheter and cycler is an effective treatment in AKI because it ensures adequate fluid status and metabolic control. However, the use of PD in AKI has several limitations, such as the need for an intact peritoneal cavity and, in emergency situations such as severe fluid overload and severe hyperkalemia, an efficacy that is lower than that with extracorporeal blood purification techniques. Metabolic, infectious, and mechanical disorders related to PD are also limitations.Among the metabolic complications of PD are hyperglycemia, hypernatremia, protein loss into the dialysate, and hypercatabolism. Hyperglycemia is caused by the use of dialysate containing high concentrations of glucose. Hypernatremia is a result of short dialysate dwell times during the rapid exchanges of high-volume PD. Protein loss into the dialysate can reach 48 g daily, worsening the nutrition status of patients already depleted by AKI. Severe hypercatabolism caused by PD remains controversial and occurs because PD methods cannot provide an adequate dialysis dose for AKI patients.Few studies have assessed the metabolic implications of PD in AKI patients. Evaluation of these implications is relatively simple, imposes no additional costs, and can provide information about the severity of the disease. Evaluation could also guide the selection of therapeutic, dialytic, and nutrition measures, preventing metabolic complications. The present manuscript describes the metabolic implications of PD and reviews the literature on how to prevent metabolic complications.

Advances in peritoneal dialysis in acute kidney injury

Peritoneal dialysis (PD) is a simple, safe, cheap, and efficient renal replacement therapy method. It can correct metabolic disorders and fluid overload in acute kidney injury (AKI) patients both in and out of the intensive care unit. Use of PD in AKI is enhanced by placement of a Tenckhoff catheter, which can be safely accomplished at the bedside. Some PD modalities, such as high-volume PD and continuous-flow PD, can provide dialysis doses and efficiency comparable to extracorporeal blood purification methods. PD is particularly suitable for neonates, children, and patients with refractory heart failure or who are otherwise hemodynamically unstable. PD should be considered in situations where systemic anticoagulation and/or vascular access are problematic. PD is limited by a lower efficiency that may produce inadequate renal replacement in larger and/or severely hypercatabolic patients. Fluid removal can be unpredictable, there is a risk of infection, and possible issues with mechanical ventilation. In this article, we discuss the use of PD in AKI, with emphasis on recent advances.

Severe hyperphosphatemia after administration of sodium-phosphate containing laxatives in children: case series and systematic review of literature

INTRODUCTION

Sodium phosphate-containing laxatives are commonly used as first-line treatment option for constipation in children and adolescents. Hyperphosphatemia is an infrequent, but potentially life-threatening complication of laxative application.

METHODS

We report a case series of three children exhibiting severe hyperphosphatemia and hypocalcemia after utilization of sodium phosphate-containing laxatives, necessitating intensive care services in two of three cases. Additionally, we reviewed 32 case reports of similar occurrences.

RESULTS

We identified 28 publications on the subject dating from 1968 to 2010. Mean age of all children in reports was 2.83 years; sex was approximately equally distributed. While 18 patients suffered from either pre-existing gastrointestinal comorbidity or other major systemic disease, no or only unrelated, minor conditions were present in ten children. One-third of patients received laxatives repeatedly before the incident. Findings associated with hyperphosphatemia include lethargy, dizziness, stiffness, tachypnea, tachycardia and severe dehydration in almost all cases, and tetany, carpopedal spasm, and prolonged QT interval in a subset. While about 80% of children recovered without residual findings, three deceased and one incurred persistent hypoxic brain damage.

CONCLUSION

Physicians should be alerted to the possibility of phosphate toxicity in children and adolescents treated with laxatives.

Continuous flow peritoneal dialysis: first experience in children with acute renal failure

BACKGROUND AND OBJECTIVES

Acute renal failure can be treated with different dialysis modalities, depending on patient characteristics and hospital resources. Peritoneal dialysis (PD) can be first choice in situations like hypotension, disturbed coagulation, or difficult venous access. The main disadvantage of PD is the relatively limited efficacy. The aim of this study was to investigate whether continuous flow peritoneal dialysis (CFPD) is a more effective treatment than conventional PD in acute renal failure.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

A pilot study was performed at The Red Cross University Hospital in Cape Town in six patients. Patients were treated with both CFPD and conventional PD for 8 to 16 hours. CFPD was performed with two bedside-placed catheters. After initial filling, dialysate flow rate (100 ml/1.73 m2 per minute) was maintained with an adapted continuous venovenous hemofiltration machine. Ultrafiltration flow rate was set at 2.5 ml/1.73 m2 per minute.

RESULTS

Mean ultrafiltration was 0.20 ml/1.73 m2 per minute with conventional PD versus 1.8 ml/1.73 m2 per minute with CFPD. Mean clearances of urea and creatinine were 5.0 and 7.6 ml/1.73 m2 per minute with conventional PD versus 15.0 and 28.8 ml/1.73 m2 per minute with CFPD, respectively. No complications occurred.

CONCLUSIONS

In this first report of CFPD in six pediatric patients with acute renal failure, CFPD was on average three to five times more effective for urea and creatinine clearance and ultrafiltration than conventional PD, without any complications observed. CFPD has the ability to improve therapy for acute renal failure.

Flow-through peritoneal dialysis in neonatal enema-induced hyperphosphatemia

Fleet enemas are hypertonic solutions with an osmotic action and a high concentration of phosphate. When retained in the human body they have a great toxic potential, causing severe hydro-electrolyte disorders in children, especially in newborns. We report the case of a previously healthy 8-day-old newborn who needed neonatal intensive care treatment after the inadvertent administration of an osmotically active hypertonic phosphate enema. Taking into account that phosphate removal by peritoneal dialysis (PD) strongly depends on total dialysate turnover, we chose continuous flow PD (CFPD) as the treatment option, with a successful outcome. Clinical experience with this dialytic modality is limited to a few case reports in pediatric and adult patients. To the best of our knowledge, we report here the first description of CFPD in the setting of acute phosphate nephropathy in the neonatal period. The modality of PD described here has potential as an alternative management option as it is a highly efficient, methodologically simple, and low-cost method without any need for sophisticated equipment. Physicians and parents should be aware of the adverse effects of a hypertonic phosphate enema and should never use these medications in infants and newborns.