How To Set A Hemofiltration Dialysis Prescription? The Experience Summary Is Here!

The long-term prognosis of hemodialysis patients has always been an important issue for doctors and patients. Although the survival rate of hemodialysis patients is increasing, the 5-year survival rate is still only 41.8%, and there is still a lot of room for improvement. Among them, cardiovascular disease is the leading cause of death in dialysis patients, accounting for more than 50%, followed by infection at 11%.

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Among the various attempts to improve the long-term prognosis of hemodialysis patients, high-volume hemodiafiltration and high-flux dialysis have gradually become excellent options, but these options have always been the white moonlight in the hearts of many dialysis patients—the envy of their The improvement brought about by the benefits, but also worried about the poor tolerance caused by its complications. Under the premise of reasonable prescription, hemodiafiltration (HDF) can still play an excellent role.

What is hemodiafiltration?

In general, the advantage of HDF over simple hemodialysis (HD) lies in the removal of medium and large molecular toxins. In the case of middle molecular toxins, many have the potential to accelerate the progression of atherosclerotic heart disease

Specifically, HD mainly completes the dialysis process through the diffusion mode, while HDF has a convective effect on this basis, which is the basis for its better removal of medium and large molecular toxins

Thanks to this advantage, the number of online HDF patients in the world or in the Asia-Pacific region is growing rapidly, with the growth rates reaching 19% and 26% respectively from 2009 to 2017, and the proportion of HDF patients in my country to the national hemodialysis patients has also reached up to 10%[1]. Taking the data from the survey report of hemodialysis patients in Shanghai from 2007 to 2014 as an example, the proportion of HDF patients increased from 7% to 52%, and most of them were treated once a week.

Is HDF, which is becoming more and more widely accepted, really that good?

What are the advantages of high-volume hemofiltration dialysis?

As early as 2007, the European Best Practice Guidelines for Blood Purification (EBPG) recommended that online HDF can make full use of the permeability of high-flux dialysis membranes, and the convection flow should be increased as much as possible under the premise of ensuring safety[3]. However, in recent years, the conclusions of a number of randomized controlled trials (RCTs) on HD and HDF have always criticized each other.

This does not mean that HDF lacks advantages compared with HD: the CONTRAST trial not only observed that the β2 microglobulin level of the online HDF group was significantly lower than that of the low-flux HD group, but also significantly reduced the risk of death when the flow rate exceeded 21.95L, and the mortality rate could be improved. 38%[4]; the Turkish trial found that all-cause and cardiovascular mortality could be reduced when the convective flow exceeded 17.4L[5]; the ESHOL trial found that the survival rate of patients in the HDF group was higher than that in the HD group, and all-cause mortality was reduced when the convective flow was 21.7L. , cardiovascular and infection-related mortality is reduced by 30%, 35%, and 55%, respectively, and the incidence of dialysis-related hypotension can be reduced by 28% [6].

Therefore, HDF with a high convective flow is indeed superior in efficacy. After a comprehensive analysis of the data of the three major RCTs, it was found that when the convective flow exceeds 23L, both all-cause mortality and cardiovascular disease-related mortality will be greatly reduced[7] ]. Although the advantages of HDF are so obvious, there are still many patients who are dissuaded by various complications or intolerance when they enter HDF treatment at the beginning. How to successfully complete each HDF treatment?

What are the common influencing factors of HDF?

There are many factors affecting the treatment of HDF, which can be roughly classified into four aspects in terms of medical practice in my country:

Patient side: vascular conditions (stable and easy-to-use vascular access), hemodynamics, hemorheological factors (hemoglobin, hematocrit, etc. do not increase blood viscosity), cardiovascular ultrafiltration rate, etc.;

Medical care side: blood flow setting, hemodialysis filter performance, anticoagulation scheme, treatment time, etc.;

Equipment side: interaction between blood and filter, dialysate flow rate, ultrafiltration transmembrane pressure and setting mode (manual/automatic), replacement fluid quality, dialyzer, dialysis machine, etc.;

Social side: medical insurance reimbursement policy, etc.

In practice, it is often necessary for doctors and nurses to select suitable patients for HDF: in addition to vascular conditions, hemodynamics, and hemorheology supporting high blood flow velocity, ideally, the expected flow rate of the arteriovenous fistula is >600ml/min, and the patient There were no complications that would increase blood viscosity, such as high hematocrit, cryoglobulinemia, and hemophilia.

Prior to this, hemodialysis equipment and consumables also need to meet certain conditions (Figure 4), among which: excellent quality of replacement fluid helps to reduce inflammatory reactions and increase the therapeutic benefit of high-capacity HDF; high-flux dialysis membrane has Helped to tolerate higher transmembrane pressure to improve filtration fraction; automated system control will be beneficial to achieve stable high-flow HDF treatment.

In practice, the treatment modes of HDF can be divided into pre-dilution replacement, post-dilution replacement, mixed dilution, and intermediate dilution according to the replacement method. At present, there is no data available for comparison of the performance of different replacement modes in terms of treatment benefits, and the impact of commonly used anterior and posterior replacements on prognosis remains to be further studied.

As for the target flow rate of HDF treatment, foreign studies have shown that the improvement of the relative survival rate of online HDF patients is flow-dependent: after the weekly flow rate reaches 56.8L, the relative survival rate of patients increases linearly with the flow rate, while when the flow rate reaches 56.8L, the relative survival rate increases linearly with the flow rate. After reaching 75L, the survival benefit is minimal, suggesting that there is no additional benefit for HDF with an extremely high flow rate. Therefore, the recommended treatment target flow rate in this study is 56.8-75.0L/week[8].

Some studies have explored the intermittent replenishment HDF (I-HDF), that is, the ultrapure dialysate is intermittently reversed into the blood during the HDF process, usually 200ml of dialysate per infusion, the infusion interval is 30min, and the infusion speed is 150ml/min. This process does not involve pre-displacement or post-displacement, and the convective flow is much lower than that of online HDF. Each treatment time is 4~5h, and the total convective flow of I-HDF is only 1.4-1.8L. This study showed that I-HDF can improve the hemodynamics of patients to a certain extent, increase the clearance of medium and large molecular solutes, improve plasma refill, and save replacement fluid [9]. However, this kind of exploration runs counter to the current mainstream pursuit of high convective flux, and its benefits still need to be further confirmed.

In addition, the latest research in my country started with the frequency of treatment and found that high-flux HD (HFHD) combined with HDF once a week can significantly improve the short-term quality of life of hemodialysis patients, improve nutritional status, reduce hospitalization time, and a number of hospitalizations, and reduce erythropoiesis. Reduce the mortality rate [10].

Summarize

In general, the key points of HDF prescription setting are nothing more than flow rate, blood flow rate, replacement mode, hemofilter, and replacement fluid flow rate. Among them, the optimal convective flow to improve the prognosis of patients can only be achieved when the convective flow reaches at least 20% of the total blood volume treated in each treatment, and the upper limit of the ultrafiltration rate in the blood flow is 25%-30% of the blood flow [11 -12].

However, although many studies have confirmed that the all-cause mortality of online HDF is significantly lower than that of HD, especially since the benefit of post-replacement online HDF is more obvious, the research evidence of anterior replacement is still relatively lacking. Therefore, the selection of the best HDF treatment mode still needs to be constantly explored in the directions of replacement mode, replacement fluid volume, treatment time, and treatment effect evaluation.

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