Daily haemodialysis, an underused technique despite its haemodynamic benefits

Abstract

Conventional three-times-weekly haemodialysis causes alternating phases of acute haemodynamic stress during the session (with a risk of hypotension and ischaemia) and chronic overload between sessions (promoting hypertension, pulmonary oedema and left ventricular hypertrophy). The risk is particularly high after the long interdialytic interval. Studies show a correlation between high ultrafiltration rates and excess mortality, suggesting that longer or more frequent dialysis — known as ‘intensive’ dialysis — could better protect the hearts and blood vessels of these patients.

We report our opinion, based on a recent analysis of the literature, regarding the benefits of daily haemodialysis.

Intensive (daily or prolonged) HD improves several parameters:

• High blood pressure: meta-analyses and the FHN trial show a significant decrease in blood pressure and left ventricular hypertrophy, with a reduction in the use of antihypertensive drugs.
• Per-dialytic hypotension: studies (FHN, RECAP, Murashima) show a decrease in the frequency of hypotensive episodes and improved haemodynamic stability due to lower volume variations.
• Myocardium: Conventional HD is particularly associated with myocardial stunning, a factor in ventricular dysfunction and mortality. Daily HD significantly reduces these contractile abnormalities.
• Post-dialysis recovery: post-session fatigue, which is common and associated with excess mortality, is greatly reduced by daily HD (LONDON and FREEDOM studies), improving quality of life and psychological well-being.

Despite these benefits, evidence remains limited due to the lack of randomised controlled trials on hard endpoints such as mortality.

Daily home HD appears to be a promising option, facilitated by new devices, although it is currently hampered by the lack of home visits by nurses to puncture the arteriovenous fistula. Nevertheless, it should be offered more widely, particularly to frail patients with refractory hypertension or those who do not tolerate conventional dialysis well.

INTRODUCTION

It is well known that dialysis patients are at very high cardiovascular (CV) risk (CVR). Indeed, classic CVR factors (age, hypertension, diabetes, etc.) are a major cause of chronic kidney disease (CKD) and therefore of dialysis. Furthermore, CKD itself is now recognized as a high CVR factor in its own right. Nationally, according to the REIN registry[1], almost two-thirds of dialysis patients are aged 65 or over (65.7%). In almost half of cases (45%), the cause of CKD is hypertension, diabetes, or renovascular disease. The prevalence of coronary artery disease (approx. 25%), heart failure (23.3%), lower limb arteritis (23%), and stroke (12.8%) is also particularly high in this population.

As a result, dialysis patients have a particularly high rate of cardiovascular morbidity and mortality. A study of the European ERA-EDTA registry[2]shows that CV mortality in the dialysis population is 8.8 times higher than in the general population. Older studies showed an even higher level of risk (10 to 20 times higher)[3].

Despite this marked cardiovascular fragility, more than 90% of dialysis patients in France undergo a discontinuous purification process: hemodialysis (HD) three times a week[1]. However, this technique is characterized by two alternating phases of hemodynamic stress: an acute stress phase during the dialysis session itself, marked by a reduction in blood volume due to ultrafiltration (UF) and rapid hydroelectrolytic variations (with a risk of hypotension, ischemic organ damage, arrhythmia, etc.), and a phase of chronic hemodynamic stress, corresponding to the interdialytic period, marked by a risk of fluid overload, hypertension, pulmonary edema, and left ventricular hypertrophy in particular[4]. Foley's study[5]demonstrated that CV morbidity and mortality are significantly more frequent in dialysis patients at the end of the longest interdialytic interval (after 2 days without dialysis).

It therefore seems theoretically beneficial, in order to limit the risk of cardiovascular events, to limit volume variations and thus "spread" UF over a longer period of time, with a view to normalizing the patient's hydrosodium pool. This is also closer to physiological renal function, which is continuous. Several studies show a positive correlation between UF rate and cardiovascular morbidity and mortality in hemodialysis patients[6][7]. In Flythe's article[6], the risk of all-cause and cardiovascular mortality increased significantly at UF rates >10 mL/kg/h. In Raimann's article[7], UF rates >760 mL/h were consistently associated with excess mortality. The "critical" UF rate appears to be lower than in Flythe's study, at around 7 mL/kg/h in patients with a dry weight of less than 100 kg. This correlation between UF and mortality was more linear when the hourly UF rate was related to the patient's body surface area rather than their dry weight. So-called "intensive" HD, which consists of longer or more frequent sessions, could provide a solution to this problem. From a conceptual point of view, it allows dialysis to be performed with less volume fluctuation and therefore less CV stress.

So-called “intensive” HD, which consists of longer or more frequent sessions, could provide a solution to this problem. From a conceptual point of view, it allows dialysis to be performed with less volume fluctuation and therefore less CV stress.

In light of recent literature, it seems to us that daily hemodialysis remains underutilized despite its apparent benefits.

BENEFITS

1. Benefits of “intensive” HD on high blood pressure

Hypertension is a frequent cause and consequence of CKD and persists in 50% to 90% of hemodialysis patients according to studies. This condition remains a major risk factor for CV morbidity and mortality in this population[8].

Meta-analyses by Liu[9]and Susantitaphong[10], of which the former compiles results from more than 22,000 patients, and the latter more than 900, show that long nocturnal hemodialysis[9]and frequent (≥3 times per week) or long (≥4 hours per session) HD[10]are superior to conventional HD (CHD, three times a week) for controlling hypertension, with a significant decrease in systolic (SBP) and diastolic (DBP) blood pressure (low in Liu's study, and -14 and -7 mmHg in Susantitaphong's study) and left ventricular hypertrophy (LVH), even though patients take fewer antihypertensive drugs.

The FHN (frequent hemodialysis network) study[11], published in 2015, analyzed the effect of intensive hemodialysis on hypertension. Patients were randomized into a group receiving HD six times a week or a group receiving CHD, with two sub-trials: one involving "daily" dialysis ("daily trial") conducted on 245 patients, and the other involving nocturnal dialysis ("nocturnal trial") with 87 patients. From the second month onwards, SBP and DBP decreased significantly in the intensive HD groups, by an average of approximately 7 and 4 mmHg, respectively, compared with CHD. This was correlated with a significant decrease in dry weight in the daytime HD group. This benefit was maintained throughout the study period (1 year), and the number of antihypertensive drugs prescribed was also slightly but significantly lower in patients included in the intensive HD arm. It should be noted that the decrease in numbers was particularly marked in the most hypertensive and anuric patients.

Several studies tend to show that blood pressure control is better with intensive HD, particularly daily HD (DHD). This is primarily because dry weight is easier to achieve gradually, spread over 5-6 days a week instead of 3. This mainly affects the volume component of hypertension.

2. Benefits of “intensive” HD on episodes of

.....