Questioning one-size-fits-all dialysis prescription: balancing dialysis prescription and residual kidney function

Abstract

Recent awareness of the viability and benefits of incremental hemodialysis is an opportunity to review clinical practices and improve the process of dialysis induction. Incremental dialysis is a standard approach in peritoneal dialysis prescription, with a focus on the quality parameter of nephroprotection. The same should apply in hemodialysis, with individualization of the prescribed extracorporeal technique: frequency, duration and intensity, in either home or center hemodialysis, are prescription variables to adjust according to the patient’s residual renal function, medical condition and psycho-social priorities. Considering that fluid balance and smooth ultrafiltration critically impact patient survival, incremental dialysis schedules need to be carefully tailored and grounded in routine residual kidney function measurement. This paper raises concerns about both the benefits of incremental dialysis and its putative detrimental effects, these being mainly dependent on the quality of the hemodialysis prescription and external economic constraints. As a comparator, incremental peritoneal dialysis is a scientifically based model to pursue, whichever the modality, based on updated concepts of patient-centered prescription and adequacy in dialytic renal replacement therapies.

INTRODUCTION

More than 60 years after Clyde Shields’ first session of chronic hemodialysis in Seattle, there are still questions about the best way to start treatment. In his foundational paper, BH Scribner had already pointed out the importance of the decline in estimated RKF on creatinine clearance, which led him to increase the frequency of sessions[1].

Chronic kidney disease (CKD) progression is a gradual process. Nonetheless, dialysis prescription is fundamentally empirical, and incidental dialysis patients’ treatment is often the same as that of those who have long periods of kidney replacement therapy (KRT), lacking individualization and adjustment to residual kidney function (RKF). The initiation of KRT is a highly disruptive life event that is made more so by the demanding standard dialysis prescriptions caused by the underappreciation of residual kidney function (RKF). While peritoneal dialysis was always grounded in the benefit of RKF protection, a relevant analysis of the Netherlands Cooperative Study on the Adequacy of Dialysis (NECOSAD)-2 clearly showed that residual renal clearance is also an important predictor of survival in hemodialysis patients[2]. Balancing KRT with RKF is the groundwork of incremental dialysis (ID). In this model, dialysis dose, either by hemodialysis (HD) or peritoneal dialysis (PD), is inversely proportional to RKF (as seen in ). This “tailored” dialysis is theoretically less aggressive than the “one size fits all” classic approach, and may therefore improve quality of life. It has also been associated with RKF preservation, though controversial data on this issue exist, showing that incremental HD may have a neutral or even detrimental effect on RKF preservation [3,4]. The lack of randomized controlled trials (RCT) of this method may be one of the reasons why ID remains a rather uncommon way of prescribing hemodialysis. This paper rases concern about ID’s potential benefits as well as its putative detrimental effects, as both are mainly dependent on the quality of the hemodialysis prescription. Results presumably depend mostly on the prescribed rate of ultrafiltration per hemodialysis session, to avoid the threat of ischemic nephrons. As a comparator, incremental dialysis in peritoneal dialysis is the standard and is presented as a scientifically based model to pursue whatever the modality, based on updated concepts of adequacy in dialytic renal replacement therapies.

Figure 1.Incremental dialysis paradigm

DEFINITION

ID its generally considered a prescription that delivers a dialysis dose inferior to the “standard,” but a sine qua non condition is that the lower dialysis dose should be mandatorily outweighed by RKF (). Incremental hemodialysis (IHD) is most commonly defined as < 3 HD sessions per week (infrequent HD) or 3 sessions of less than 4 hours[5],[6]. However, ID is not synonymous with infrequent or shorter dialysis, as the adjustment of dialysis intensity per session (measured as small solute clearance such as Kt/V urea) is also one way of achieving ID[7],[8]. In the hemodialysis field, individualization is seldom done, and the standard of quality remains fixed on the schedule of 3 HD sessions 4 hours each /week, which does not align with the updated concept of adequacy[9].

On the other hand, in peritoneal dialysis, the systematic schedule of 4 exchanges per day with 2L solutions each has long been abandoned and substituted with incremental regimens of continuous ambulatory (for example, 3 exchanges /day, with variable intra-peritoneal volumes) or automated peritoneal dialysis “a la carte,” according to the residual renal function and patient-specific medical conditions and lifestyle options. In peritoneal dialysis, the focus of the prescription is on nephroprotection, as it is known that each mL of renal creatinine clearance is qualitatively more important and has more impact on survival than the same amount of peritoneal creatinine clearance. Dialysis prescription therefore targets supplementary doses of small solutes and fluid removal on top of residual renal function, still taking into account that standard measures of KT/V urea neglect the clinical relevance of the removal of other toxins, such as phosphate and sodium[10],[11].

Therefore, incremental dialysis is in fact an individualized prescription, with adjustments in the frequency, duration, and intensity of sessions according to patient renal reserve and psycho-social demands. The question is which targets it aims to achieve and in what way those targets are conditioned by modulating such prescription variables. Prioritization of targets by clinicians and negotiation of patients’ priorities is the unsolved challenge, but the authors argue that HD should progress and mimic the quality achievements of incremental PD prescription.

Use of incremental dialysis regimens

The world prevalence of incremental hemodialysis (IHD) is unknown. In the USA, infrequent HD is used in as much as 6% of HD patients. Interestingly, an American prospective cohort of 20,000 incident dialysis patients showed that the prevalence of ID (twice-weekly hemodialysis) was 2%, although half of patients had enough RKF to allow ID[12]-[15]. On the other hand, as result of economic constraints, some countries have a high prevalence of infrequent hemodialysis. But the prescription of less frequent hemodialysis regardless of RKF cannot be misclassified as ID because it lacks the pivotal balance of RKF and RRT. Consequently, the potential ID harms identified in some studies must be analyzed carefully[16].

In the field of peritoneal dialysis, the prescription of incremental dialysis has largely been advocated based on scientific evidence that considers routine residual renal function measurement, residual and peritoneal small solute clearance, and fluid balance. Such

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