Should Patients With AKI Use Continuous Kidney Replacement Therapy Or Intermittent Hemodialysis?

The mode of renal replacement therapy (KRT) for patients with acute kidney injury (AKI) has been debated for decades. The KDIGO AKI guidelines ten years ago included both intermittent and continuous renal replacement therapy (CKRT) modes of recommendation, but is this guideline still applicable ten years later? Some scholars now believe that CKRT is an ideal intervention method for patients with AKI, while others believe that intermittent hemodialysis should also be considered.

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On February 9, 2023, CJASN released the debate summary of scholars and experts from many medical institutions and dialysis centers in the United States. In this debate, both pros and cons discussed the impact of CKRT and intermittent hemodialysis on AKI patients from multiple dimensions and agreed that KRT needs to be provided in a patient-centered manner.

KRT history review

CKRT has been used clinically for 40 years, initially using continuous arteriovenous hemofiltration (CAVH). CAVH is a simple therapy in which extracorporeal circulation of blood is driven by a pressure gradient between the arteriovenous circulation without pumps or pressure monitors. Therefore, in the early stages of KRT development, the initial options for emergency initiation of dialysis were limited to intermittent hemodialysis or peritoneal dialysis, and the applicable population for intermittent hemodialysis was only hemodynamically stable patients.

In the ensuing decades, both intermittent hemodialysis and CKRT underwent a dramatic shift. For example, fibrous hemodialysis membranes have been replaced by more biocompatible synthetic membranes, standard buffers have been changed from acetate to bicarbonate, and dialysates have been improved. This series of improvements makes CKRT more suitable for patients with hemodynamic instability.

With the advancement of technology, there is currently a third KRT mode suitable for AKI patients, which is the mixed mode. There are two types of mixed mode: ① patients receive intermittent dialysis, but the flow rate of dialysate and blood is slowed down, and the single dialysis time is extended from 8h to 16h; ② patients receive CKRT, but ultrafiltration and/or dialysate flow rate, daily treatment for 10-12 hours, these two methods are collectively referred to as extended intermittent renal replacement therapy (PIKRT).

In addition to KRT, other critical rescue equipment has improved, such as ventilators, ventricular assist devices, and extracorporeal membrane oxygenation. Therefore, a growing number of experts have debated which mode of dialysis should be used in patients with AKI. The KDIGO guidelines ten years ago pointed out that various dialysis methods, such as intermittent hemodialysis, CKRT, and PIKRT, are ideal KRT for patients. For patients with unstable blood flow, CKRT should be used in preference to other therapies. But this is a clinical guide from ten years ago, can it guide the current clinical treatment?

Pros: CKRT should be the first choice for patients with AKI

In guidelines from a decade ago, CKRT or intermittent hemodialysis was not an either-or choice. Today, ten years later, some scholars believe that based on current evidence, patients with AKI should prefer CKRT to other modalities. Scholars from the Australian and New Zealand Society of Critical Care Medicine believe that if patients are allowed to switch dialysis modes during the study, such as changing from intermittent hemodialysis to CKRT, then the study is essentially a cross-comparison rather than a controlled study.

Similarly, the timing of KRT initiation in patients with AKI will vary depending on the dialysis mode. The AKIKI study has drawn more criticism because half of the patients received intermittent hemodialysis. If only the "one-to-one" study of dialysis mode is judged, then the long-term prognosis of CKRT tends to be better than that of other dialysis modes. Some scholars and researchers believe that CKRT is the first choice for patients with AKI.

Why is CKRT superior to other dialysis modalities? Some scholars believe that it can be explained by the fable of the tortoise and the hare. The characteristic of CKRT is that it can slowly but steadily remove uremic toxins and excess blood volume, gradually correct electrolyte and acid-base disorders, and minimize the impact on hemodynamics. Intermittent hemodialysis is to quickly correct the above disorders but has a greater impact on hemodynamics. In the short term, the rabbit (intermittent hemodialysis) appears to be winning, but in the long run, the winner is the tortoise (CKRT).

However, these scholars also agree that intermittent hemodialysis can also achieve better curative effects for patients with brain injury or liver failure with increased intracranial pressure, but this is limited to AKI patients with special comorbidities. And compared with CKRT, intermittent hemodialysis has no significant advantage. In addition, the scholars of the Zhengfang team emphasized that intermittent hemodialysis is the best choice for AKI patients with drug or poison poisoning.

Cons: Patients with AKI should choose intermittent dialysis mode

Scholars on the opposite side believe that the current data do not clarify which dialysis mode is most suitable for AKI patients. Although Zhengfang believes that the research design of some clinical studies has limitations, most of the clinical research data show that no matter what type of dialysis is used, there is no significant difference in the short-term and long-term recovery of renal function, and there is no significant difference in the risk of death.

However, in some studies, researchers did not provide patients with AKI with standard intermittent hemodialysis but extended the duration of dialysis. Therefore, in the debate, the opponents believe that if AKI patients need intermittent hemodialysis, the treatment time should be extended from 3~4h to 5~5.5h to achieve a similar effect to CKRT. The affirmative part of the experts also agreed with this idea.

Scholars on the opposite side also pointed out that only including observational studies, it can be found that under actual clinical conditions, the renal function recovery of AKI patients using intermittent hemodialysis is better than CKRT, and the risk of death is lower, but CKRT can make more patients Avoid future progression to dependent dialysis patients. After adjusting for factors such as baseline information, the results of these observational studies still have confounding factors, which have biased the results.

Finally, experts reminded us that the current research did not compare the cost of the two dialysis methods in detail. This is due to differences in baseline, study design, and medical institutions in existing studies, making it difficult to "fairly" compare the costs of the two dialysis methods. However, in actual clinical work, the cost issue should be considered. In some cases, cost, rather than efficacy, is a major factor in medical decision-making.

Summarize

After sorting out the existing research and the views of relevant scholars, Professor Paul M. Palevsky from the Department of Nephrology, Pittsburgh School of Medicine (also the moderator of this debate) summarized the views of both sides.

First of all, both pros and cons agree that it is necessary to focus on AKI patients, provide the best possible treatment methods, and optimize clinical research based on this concept. However, existing research cannot provide reasonable answers to the following questions:

①Which AKI patients are the ideal research population?

② What is the difference between the applicable population?

③Will the starting timing of dialysis affect the results of dialysis?

④Should the initiation timing of intermittent hemodialysis and CKRT be different?

⑤ For AKI patients, how to judge the curative effect of KRT? What is its key prognosis?

The above questions should be the main direction of AKI-related research in the next few years.

Second, it would be incorrect to define this debate solely as "for or against" a certain dialysis model. For patients with a sharp decline in renal function, doctors should adopt an appropriate dialysis mode according to their conditions. For example, AKI patients with drug/toxin poisoning should choose intermittent hemodialysis, but need to slowly remove uremic toxins and correct electrolytes and acid Patients with alkalosis require CKRT.

In general, the KDIGO AKI guidelines ten years ago still seem to be able to guide the current clinical practice, but in a specific practice, doctors should understand and clarify the individual conditions of patients and the etiology of AKI before choosing the best dialysis mode for them.

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