Effect of acetate-free biofiltration with a potassium-profiled dialysate on the control of cardiac arrhythmias in patients at risk: a pilot study

The Nephrologist's Role in the Collaborative Multi-Specialist Network Taking Care of Patients with Diabetes on Maintenance Hemodialysis: An Overview

Diabetes mellitus is the leading cause of renal failure in incident dialysis patients in several countries around the world. The quality of life for patients with diabetes in maintenance hemodialysis (HD) treatment is in general poor due to disease complications. Nephrologists have to cope with all these problems because of the “total care model” and strive to improve their patients’ outcome. In this review, an updated overview of the aspects the nephrologist must face in the management of these patients is reported. The conventional marker of glycemic control, hemoglobin A1c (HbA1c), is unreliable. HD itself may be responsible for dangerous hypoglycemic events. New methods of glucose control could be used even during dialysis, such as a continuous glucose monitoring (CGM) device. The pharmacological control of diabetes is another complex topic. Because of the risk of hypoglycemia, insulin and other medications used to treat diabetes may need dose adjustment. The new class of antidiabetic drugs dipeptidyl peptidase 4 (DPP-4) inhibitors can safely be used in non-insulin-dependent end-stage renal disease (ESRD) patients. Nephrologists should take care to improve the hemodynamic tolerance to HD treatment, frequently compromised by the high level of ultrafiltration needed to counter high interdialytic weight gain. Kidney and pancreas transplantation, in selected patients with diabetes, is the best therapy and is the only approach able to free patients from both dialysis and insulin therapy.

Fluctuations in plasma potassium in patients on dialysis

Plasma potassium concentration is maintained in a narrow range to avoid deleterious electrophysiologic consequences of both abnormally low and high levels. This is achieved by redundant physiologic mechanisms, with the kidneys playing a central role in maintaining both short-term plasma potassium stability and long-term total body potassium balance. In patients with end-stage renal disease, the lack of kidney function reduces the body’s ability to maintain normal physiologic potassium balance. Routine thrice-weekly dialysis therapy achieves long-term total body potassium mass balance, but the intermittent nature of dialytic therapy can result in wide fluctuations in plasma potassium concentration and consequently contribute to an increased risk of arrhythmogenicity. Various dialytic and nondialytic interventions can reduce the magnitude of these fluctuations, but the impact of such interventions on clinical outcomes remains unclear.

A simple modification of dialysate potassium: its impact on plasma potassium concentrations and the electrocardiogram

Background

Sudden death is frequent in haemodialysis (HD) patients. Both hyperkalaemia and change of plasma potassium (K) concentrations induced by HD could explain this. The impact of increasing dialysate K by 1 mEq/L on plasma K concentrations and electrocardiogram (ECG) results before and after HD sessions was studied.

Methods

Patients with pre-dialysis K >5.5 mEq/L were excluded. ECG and K measurements were obtained before and after the first session of the week for 2 weeks. Then, K in the dialysate was increased (from 1 or 3 to 2 or 4 mEq/L, respectively). Blood and ECG measurements were repeated after 2 weeks of this change.

Results

Twenty-seven prevalent HD patients were included. As expected, a significant decrease in K concentrations was observed after the dialysis session, but this decrease was significantly lower after the switch to an increased dialysate K. The pre-dialysis K concentrations were not different after changing, but post-dialysis K concentrations were higher after switching (P < 0.0001), with a lower incidence of post-dialysis hypokalaemia. Regarding ECG, before switching, the QT interval (QT) dispersion increased during the session, whereas no difference was observed after switching. One week after switching, post-dialysis QT dispersion [38 (34-42) ms] was lower than post-dialysis QT dispersion 2 weeks and 1 week before switching [42 (38-57) ms, P = 0.0004; and 40 (35-50) ms, P = 0.0002].

Conclusions

A simple increase of 1 mEq/L of K in the dialysate is associated with a lower risk of hypokalaemia and a lower QT dispersion after the dialysis session. Further study is needed to determine if such a strategy is associated with a lower risk of sudden death.

Optimizing dialysate potassium

Potassium shifts in thrice weekly HD patients are likely a reversible cause of arrhythmia and sudden cardiac death. In general, a dialysate potassium <2.0 mmol/L should be avoided, and many patients with dialysate potassium of 2 mmol/L could safely be adjusted upwards. The ideal predialysis serum potassium should be around 5.0 mmol/L. Trends in serum potassium and not single values, should inform chronic changes of dialysate potassium prescription. Atypical values should be dealt with as a one off, but should not lead to chronic bath changes. Referral to a renal dietician for counseling to limit dietary potassium intake is vital to prevent recurrence of these atypical episodes. Finally, facilities should develop and implement a formal and reliable way to alert the physician about possible potassium bath mismatching. This facility level approach works best if a policy is developed and endorsed by all involved stakeholders.

[Cardiac arrest in dialysis patients: Risk factors, preventive measures and management in 2015]

Patients undergoing hemodialysis have a 10 to 20 times higher risk of sudden cardiac arrest (SCA) than the general population. Sudden cardiac death is a rare event (approximately 1 event per 10,000 sessions) but has a very high mortality rate. Epidemiological data comes almost exclusively from North American studies; there is a great lack of European data on the subject. Ventricular arrhythmia is the main mechanism of sudden cardiac deaths in dialysis patients. These patients develop increased sensitivity mainly due to a high prevalence of severe ischemic heart disease and left ventricular hypertrophy and to a frequent trigger event: electrolytic and plasma volume shifts during dialysis sessions. Unfortunately, accurate predictive markers of SCA do not exist, however some primary prevention trials using beta-blockers or angiotensin II receptor blockers are encouraging, while the use of implantable cardioverter defibrillators in the population of chronic dialysis patients remains controversial. Identification of patients at risk, minimizing trigger events such as electrolytic shifts and improving team skills in the diagnosis and initial resuscitation with the latest recommendations from 2010 seem necessary to reduce incidence and improve survival in this high risk population. Organization of European studies would also allow a more accurate view of this reality in our dialysis units.

Low dialysate potassium concentration: an overrated risk factor for cardiac arrhythmia?

Serum potassium concentrations rise with dietary potassium intake between dialysis sessions and are often at hyperkalemic levels by the next session. Conversely, potassium concentrations fall during each hemodialysis, and sometimes reach hypokalemic levels by the end. Low potassium dialysate, which rapidly decreases serum potassium and often brings it to hypokalemic levels, is almost universally considered a risk factor for life-threatening arrhythmias. While there is little doubt about the threat of lethal arrhythmias due to hyperkalemia, convincing evidence for the danger of low potassium dialysate and rapid or excess potassium removal has not been forthcoming. The original report of more frequent ventricular ectopy in early dialysis that was improved by reducing potassium removal has received very little confirmation from subsequent studies. Furthermore, the occurrence of ventricular ectopy during dialysis does not appear to predict mortality. Studies relating sudden deaths to low potassium dialysate are countered by studies with more thorough adjustment for markers of poor health. Dialysate potassium concentrations affect the excursions of serum potassium levels above or below the normal range, and have the potential to influence dialysis safety. Controlled studies of different dialysate potassium concentration and their effect on mortality and cardiac arrests have not been done. Until these results become available, I propose interim guidelines for the setting of dialysate potassium levels that may better balance risks and benefits.

Hyperkalemia in hemodialysis patients

Hyperkalemia contributes significantly to high mortality among ESRD patients. Excess intake and inadequate removal are the most common etiologies in HD patients. Although dialysis is the definitive treatment, classical medical therapy must be employed as a temporizing measure to acutely lower serum potassium. Reducing potassium intake through dietetic/nutritional support is critical to reducing the K+ load in ESRD patients and preventing this condition.