Calcium and phosphate balance in adolescents on home nocturnal haemodialysis

Monitoring dialysis adequacy: history and current practice

Dialysis adequacy for pediatric patients has largely followed the trends in adult dialysis by judging the success or adequacy of peritoneal or hemodialysis with urea kinetic modeling. While this provides a starting point to establish a dose of dialysis, it is clear that urea is only part of the picture. Many clinical parameters and interventions now have been identified that are just as impactful on mortality and morbidly as urea clearance. As such, our concept of adequacy is evolving to include non-urea parameters and assessing the impact that following an "adequate therapy" has on patient lives. As we move to a new era, we consider the impact these therapies have on patients and how it affects the quality of their lives; we must take these factors into consideration to achieve a therapy that is not just adequate, but livable.

Reducing the burden of cardiovascular disease in children with chronic kidney disease: prevention vs. damage limitation

Cardiovascular disease (CVD) is a life-limiting condition in patients with chronic kidney disease (CKD) and is rapidly progressive, especially in those with stage 5 CKD and on dialysis. Cardiovascular mortality, although reducing, remains at least 30 times higher than in the general pediatric population. The American Heart Association guidelines for cardiovascular risk reduction in high-risk pediatric patients has stratified pediatric CKD patients in the "high risk" category for the development of CVD, with associated pathological and/or clinical evidence for manifest coronary disease before 30 years of age. While improving patient survival is a key priority, other patient-related outcomes, such as psychosocial development, quality of life and growth are of major importance to children and their caregivers. Once vascular damage or calcification has developed, there are no data to suggest that they can be reversed. Treatments such as intensified dialysis and transplantation may attenuate the progression of subclinical cardiovascular disease, but no treatment to date has shown that the inexorable progression of CVD in CKD can be reversed. Thus, our management must focus on early diagnosis and robust preventative strategies to give our patients the best chance of optimal cardiovascular health and survival. In this review, the pathophysiology and importance of preventing the development of CVD in CKD is discussed.

Bone evaluation in paediatric chronic kidney disease: clinical practice points from the European Society for Paediatric Nephrology CKD-MBD and Dialysis working groups and CKD-MBD working group of the ERA-EDTA

Mineral and bone disorder (MBD) is widely prevalent in children with chronic kidney disease (CKD) and is associated with significant morbidity. CKD may cause disturbances in bone remodelling/modelling, which are more pronounced in the growing skeleton, manifesting as short stature, bone pain and deformities, fractures, slipped epiphyses and ectopic calcifications. Although assessment of bone health is a key element in the clinical care of children with CKD, it remains a major challenge for physicians. On the one hand, bone biopsy with histomorphometry is the gold standard for assessing bone health, but it is expensive, invasive and requires expertise in the interpretation of bone histology. On the other hand, currently available non-invasive measures, including dual-energy X-ray absorptiometry and biomarkers of bone formation/resorption, are affected by growth and pubertal status and have limited sensitivity and specificity in predicting changes in bone turnover and mineralization. In the absence of high-quality evidence, there are wide variations in clinical practice in the diagnosis and management of CKD-MBD in childhood. We present clinical practice points (CPPs) on the assessment of bone disease in children with CKD Stages 2-5 and on dialysis based on the best available evidence and consensus of experts from the CKD-MBD and Dialysis working groups of the European Society for Paediatric Nephrology and the CKD-MBD working group of the European Renal Association-European Dialysis and Transplant Association. These CPPs should be carefully considered by treating physicians and adapted to individual patients' needs as appropriate. Further areas for research are suggested.

Nocturnal home hemodialysis in children: Advantages, implementation, and barriers

Chronic kidney disease and end-stage renal disease (ESRD) in children are major health concerns worldwide with increasing incidence and prevalence. Renal replacement therapies and kidney transplants have remarkably improved the management of patients with ESRD in both adult and pediatric populations. Kidney transplant has the best patient outcomes, but many a time it has a considerable waiting period. In the meantime, the majority of patients with pediatric ESRD are dependent on dialysis. The conventionally utilized hemodialysis regimen is the three times weekly, in-center hemodialysis. Many studies have demonstrated the unfavorable long-term morbidity associated with the conventional regimen. Intensified dialysis programs, which include extended nocturnal hemodialysis or short daily hemodialysis, are being increasingly advocated over the past two decades. In addition to having much better clinical outcomes as compared with the conventional regimen, the flexibility to provide dialysis at home serves as a great incentive. PubMed/Medline, Embase and Cochrane databases for literature on nocturnal home hemodialysis in children with ESRD were extensively searched. Contrary to the noticeable literature available on adult home hemodialysis, a small number of studies exist in the pediatric population. In this review, the benefits, implementation and associated barriers of nocturnal home hemodialysis in children were addressed.

The dietary management of calcium and phosphate in children with CKD stages 2-5 and on dialysis-clinical practice recommendation from the Pediatric Renal Nutrition Taskforce

In children with chronic kidney disease (CKD), optimal control of bone and mineral homeostasis is essential, not only for the prevention of debilitating skeletal complications and achieving adequate growth but also for preventing vascular calcification and cardiovascular disease. Complications of mineral bone disease (MBD) are common and contribute to the high morbidity and mortality seen in children with CKD. Although several studies describe the prevalence of abnormal calcium, phosphate, parathyroid hormone, and vitamin D levels as well as associated clinical and radiological complications and their medical management, little is known about the dietary requirements and management of calcium (Ca) and phosphate (P) in children with CKD. The Pediatric Renal Nutrition Taskforce (PRNT) is an international team of pediatric renal dietitians and pediatric nephrologists, who develop clinical practice recommendations (CPRs) for the nutritional management of various aspects of renal disease management in children. We present CPRs for the dietary intake of Ca and P in children with CKD stages 2-5 and on dialysis (CKD2-5D), describing the common Ca- and P-containing foods, the assessment of dietary Ca and P intake, requirements for Ca and P in healthy children and necessary modifications for children with CKD2-5D, and dietary management of hypo- and hypercalcemia and hyperphosphatemia. The statements have been graded, and statements with a low grade or those that are opinion-based must be carefully considered and adapted to individual patient needs based on the clinical judgment of the treating physician and dietitian. These CPRs will be regularly audited and updated by the PRNT.

Home hemodialysis in children

Pediatric home hemodialysis is infrequently performed despite a growing need globally among patients with end-stage renal disease who do not have immediate access to a kidney transplant. In this review, we expand the scope of the Implementing Hemodialysis in the Home website and associated supplement published previously in Hemodialysis International and offer information tailored to the pediatric population. We describe the experience and outcomes of centers managing pediatric patients, and offer recommendations and practical tools to assist clinicians in providing quotidian dialysis for children, including infrastructural and staffing needs, equipment and prescriptions, and patient selection and training.

Hemodiafiltration in a pediatric nocturnal dialysis program

BACKGROUND

To overcome the deleterious consequences of conventional dialysis, intensified dialysis programs have been developed and their feasibility and beneficial effects in children demonstrated. To investigate whether such a program can be further improved, we implemented hemodialfiltration within an established pediatric in-center, nocturnal hemodialysis program.

METHODS

After being started on conventional hemodialysis (HD), seven patients were switched to intermittent nocturnal hemodialysis (NHD) for 3 months, then to intermittent nocturnal online-hemodiafiltration (NHDF) for a further 3 months and finally back to NHD. Uremia-associated parameters, predialytic blood pressure, intradialytic events, protein catabolic rate and levels of albumin, vitamins and trace elements were investigated. Dialysis-related medication and dietary restrictions were also registered.

RESULTS

Phosphate and intact parathyroid hormone levels were reduced after the switch from HD to NHD and NHDF. Dialysis dose (Kt/V) was increased in patients on NHD and NHDF; however, Kt/V was significantly higher with NHDF than NHD. Blood pressure was significantly reduced in patients on NHD and NHDF despite the reduction in antihypertensive medication; albumin levels were significantly higher on NHD and NHDF, indicating improved nutritional status; protein catabolic rate was also increased. Vitamins and trace elements remained unchanged. All dietary restrictions could be lifted in patients on NHD and NHDF.

CONCLUSIONS

The introduction of a nocturnal dialysis program to an existing intensified HD program significantly improved the uremia-associated parameters, nutrition and hemodynamic stability of our seven patients. At least during our observational period, hemodiafiltration was able to further improve the existing HD program by increasing the Kt/v.

Intensified hemodialysis in adults, and in children and adolescents

BACKGROUND

There are now almost 70 000 dialysis patients in Germany. Conventional hemodialysis does not adequately compensate for malnutrition, arterial hypertension, renal osteopathy, and diminished performance ability. Various strategies for intensified hemodialysis have been implemented in an attempt to lower the considerable morbidity and mortality of end-stage renal failure.

METHOD

We selectively review the literature on intensified dialysis in adults, children, and adolescents.

RESULTS

In a randomized, controlled trial (RCT), a group of patients undergoing conventional dialysis was compared to a group undergoing brief, daily dialysis. Daily dialysis significantly improved the combined endpoint of left-ventricular hypertrophy or death (hazard ratio [HR] 0.61). In contrast, another, retrospective study found daily dialysis to be associated with higher mortality (15.6 vs. 10.9 deaths, HR 1.6). A prospective case-control study found nocturnal intermittent hemodialysis to be associated with lower mortality than conventional dialysis (1.77 vs. 6.23 per 100 patient-years); this result was confirmed in a further, retrospective study. An RCT on nocturnal dialysis performed every night revealed a significant regression of left-ventricular mass, yet the patients' quality of life improved only in individual domains specifically related to renal function. Small-scale studies of intensified hemodialysis in children and adolescents have found that it leads to a higher growth rate and weight gain.

CONCLUSION

Intensified hemodialysis techniques improve arterial blood pressure, uremia-associated variables, and psychosocial variables. They also lower the necessary doses of antihypertensive drugs and phosphate binders. Dietary restrictions need not be as stringent. Further prospective trials are needed for a reliable assessment of the effect of intensified hemodialysis on mortality and quality of life.

Chronic kidney disease: mineral and bone disorder in children

Childhood and adolescence are crucial times for the development of a healthy skeletal and cardiovascular system. Disordered mineral and bone metabolism accompany chronic kidney disease (CKD) and present significant obstacles to optimal bone strength, final adult height, and cardiovascular health. Early increases in bone and plasma fibroblast growth factor 23 (FGF23) are associated with early defects in skeletal mineralization. Later in the course of CKD, secondary hyperparathyroidism--caused by a combination of declining calcitriol values and phosphate retention--results in high-turnover renal osteodystrophy whereas increased levels of both phosphate and FGF23 contribute to cardiovascular disease. Treatment of hyperphosphatemia and secondary hyperparathyroidism improves high-turnover bone disease but fails to correct defects in skeletal mineralization. Because overtreatment may result in adynamic bone disease, growth failure, hypercalcemia, and progression of cardiovascular calcifications, therapy therefore must be titrated carefully to maintain optimal serum biochemical parameters according to stage of CKD. Newer therapeutic agents and new treatment paradigms may suppress serum PTH levels effectively while limiting intestinal calcium absorption and skeletal FGF23 stimulation and may provide future therapeutic alternatives for children with CKD.

Home haemodialysis

Haemodialysis (HD) began as an intensive care treatment offered to a very select number of patients in an attempt to keep them alive. Outcomes were extremely poor, and the procedure was cumbersome and labor intensive. With increasing expertise and advances in dialysis equipment, HD is now recognised as a life-sustaining treatment that is considered a standard of care for children with end stage renal disease (ESRD). Assessment of efficacy has evolved from mere survival, through achieving minimal standards of "adequate" dialysis with reduced morbidity, towards the provision of "optimal dialysis", which includes attempts to more closely mimic normal renal function, and of individualised care that maximizes the patient's health, psychosocial well-being and life potential. There is a renewed interest in dialysis, and the research profile has extended, exploring themes around convective versus diffusive treatments, HD time versus frequency and home versus in-centre dialysis. The results thus far have led dialysis care full circle from prolonged, home-based therapies to shorter, intense in-centre dialysis back to the belief that long or frequent HD at home achieves the best outcomes.

Approach to the hypophosphatemic patient

Hypophosphatemia is commonly missed due to nonspecific signs and symptoms, but it causes considerable morbidity and in some cases contributes to mortality. Three primary mechanisms of hypophosphatemia exist: increased renal excretion, decreased intestinal absorption, and shifts from the extracellular to intracellular compartments. Renal hypophosphatemia can be further divided into fibroblast growth factor 23-mediated or non-fibroblast growth factor 23-mediated causes. Proper diagnosis requires a thorough medication history, family history, physical examination, and assessment of renal tubular phosphate handling to identify the cause. During the past decade, our understanding of phosphate metabolism has grown greatly through the study of rare disorders of phosphate homeostasis. Treatment of hypophosphatemia depends on the underlying disorder and requires close biochemical monitoring. This article illustrates an approach to the hypophosphatemic patient and discusses normal phosphate metabolism.

Intensive hemodialysis: normalizing the "unphysiology" of conventional hemodialysis?

Interest in intensified hemodialysis (HD) regimens is increasing internationally, as there is growing evidence that they are associated with improved outcomes. Appreciation that conventional hemodialysis (CHD), delivered as 4-hour sessions three times a week, is not providing optimal physiological replacement of renal function has led to the development of intensified dialysis therapies. These include long intermittent hemodialysis typically lasting 6-8 hours and delivered three times a week, short daily hemodialysis, providing more frequent sessions 4-7 days a week lasting 2-3.5 hours, and nocturnal hemodialysis, performed 5-7 days a week for 6-8 hours. Studies evaluating outcomes from these programs have indicated superior results to those achieved with CHD, including favorable modifications of cardiovascular risk factors and improvements in a variety of clinical measures. The objective of this review is to present available evidence supporting the hypothesis that in an attempt to provide a "more normal physiology," intensified HD regimens achieve outcomes superior to those historically achieved with CHD.

Mineral metabolism and bone abnormalities in children with chronic renal failure

Abnormalities in mineral metabolism and changes in skeletal histology may contribute to growth impairment in children with chronic renal failure. Hyperphosphatemia, hypocalcemia, metabolic acidosis, alterations in vitamin D and IGF synthesis and parathyroid gland dysfunction play significant roles in the development of secondary hyperparathyroidism and subsequently, bone disease in renal failure. The recent KDIGO conference has made recommendations to consider this as a systemic disorder (chronic kidney disease-mineral bone disorder) and to standardize bone histomorphometry to include bone turnover, mineralization and volume (TMV). The use of DXA to assess bone mass is controversial in children with chronic renal failure. Questions arise regarding the accuracy of bone measurements and difficulty in data interpretation especially in children with renal failure who are not only growth retarded but often have pubertal delay and osteosclerosis. The validity and feasibility of new modalities of skeletal imaging which can detect changes in both trabecular and cortical bone are currently being investigated in children. The management of mineral abnormalities and bone disease in chronic renal failure is multifactorial. To manage hyperphosphatemia, dietary phosphate restriction accompanied by intake of calcium-free and metal-free phosphate binding agents are widely utilized. Vitamin D analogs remain the primary therapy for secondary hyperparathyroidism, although the use of the less hypercalcemic agents is preferred due to concerns of calciphylaxis and vascular calcification. Future clinical studies are needed to evaluate the long-term effects of calcimimetic agents and bisphosphonate therapy in children with chronic renal failure.

Impact of water quality and dialysis fluid composition on dialysis practice

An essential but frequently neglected aspect of dialysis treatment is the dialysis fluid produced by blending treated tap water with concentrated solutions containing electrolytes and buffer. Chemical and microbiological contaminants as well as the electrolyte and buffer composition of the dialysis fluid play major roles in the induction or modulation of morbidity associated with regular dialysis therapy.

Frequent hemodialysis in children

Frequent hemodialysis is currently conducted in a limited number of pediatric dialysis centers. However, the preliminary experience with children who have undergone procedures such as "daily" intensive hemodiafiltration and nocturnal hemodialysis has been positive, with the allowance for unrestricted diets and fluid intake, the lack of need for phosphate binders, excellent metabolic and blood pressure control, and, in the case of hemodiafiltration, excellent growth. The provision of frequent daily hemodialysis with the NxStage System has also recently been introduced to pediatrics. An overview about what is currently understood regarding the technical and clinical application of these approaches to therapy for children with end-stage renal disease form the basis for this article and highlight the impact of the procedures to date and the need for additional experience and collaborative data collection.

How have the past 5 years of research changed clinical practice in paediatric nephrology?

Clinical practice in paediatric nephrology is continuously evolving to mirror the research output of the 21st century. The management of antenatally diagnosed renal anomalies, urinary tract infections, nephrotic syndrome and hypertension is becoming more evidence based. Obesity and related hypertension is being targeted at primary and secondary care. The evolving field of molecular and cytogenetics is discovering genes that are facilitating clinicians and families with prenatal diagnoses and understanding of disease processes. The progression of chronic kidney disease in childhood to end-stage renal failure (ESRF) can be delayed using medical treatment to reduce proteinuria and treat hypertension. Pre-emptive living-related renal transplantation has become the treatment of choice for children with ESRF, thereby reducing the morbidity and mortality associated with peritoneal and haemodialysis. Although peritoneal dialysis, which is performed in the patient's home, is the preferred modality for children for whom there is no living or deceased donor for transplantation, home nocturnal haemodialysis is becoming a feasible option. Imaging modalities with the use of magnetic resonance and computerised tomography are continuously improving. As mortality for renal and vasculitic diseases improves, the gauntlet is now thrown down to reduce morbidity with secondary prevention of longer-term complications such as atherosclerosis and hyperlipidaemia. Clinical and drug trials in the fields of hypertension, nephrotic syndrome, systemic lupus erythematosus, vasculitis and transplantation are producing more effective treatments, thereby reducing the morbidity resulting from the disease processes and the side effects of drugs.