**4. Arrhythmia in patients on dialysis**

Arrhythmias are very common in patients with CRF undergoing dialysis, and they are the cause of a significant percentage of sudden deaths of cardiac origin (Meier et al., 2001). Arrhythmias are more common in certain groups of patients: subjects with heart disease, left ventricular hypertrophy, coronary disease, heart valve disorders, high blood pressure or diabetes, and elderly patients.

Haemodialysis causes an arrhythmogenic effect (Meier et al., 2001). Dialysis is known to be related to QT prolongation in the ECG tracing (this being a risk marker for serious ventricular arrhythmia) (Genovesi et al., 2003).

Arrhythmia in dialysis may be related to sudden ion or blood pressure fluctuations. K+ is a particularly arrhythmogenic ion (Kovesdy et al., 2007), related to the membrane potential, which is involved in cardiac cell depolarisation. K+ experiences sudden changes during haemodialysis, and a sharp drop can induce arrhythmia (Cupisti et al., 1999). In some cases, and despite diet advice or medical therapy, patients arrive for their dialysis session with high serum K+ levels, and experience a sudden decrease during the early part of the session. This has been related to the appearance of arrhythmias or to the worsening of pre-existing arrhythmias: induction or worsening of ventricular extrasystoles, QT prolongation (Cupisti

Acetate Free Biofiltration with Potassium Profiled Dialysate (AFB-K) 231

of treatment the serum K+ levels of the patients were lower in AFB than with AFB-K. The

Our group conducted a pilot study (Muñoz et al., 2008) at the start of the introduction of the AFB-K technique. The purpose of this study was to evaluate its efficacy and safety, analyse the decrease in blood K+, and establish whether a decrease in arrhythmias occurs compared with AFB involving constant K+ (AFB). We subsequently used the technique as an

Twelve patients were included in the study (mean age 79 years; 5 males and 7 females). The subjects had arrhythmia or were at high risk of developing it, because of their old age, with high blood pressure (n=12), left ventricular hypertrophy (n=12), valve disease (n=8), coronary heart disease (n=3), diabetes mellitus (n=3) or paroxysmal atrial fibrillation

A cross-over design was used, each subject serving as his or her own control. The subjects were dialysed for three weeks with AFB involving constant K+, and for three weeks with potassium profiled AFB. At first dialysis in week 3 with each technique we conducted laboratory tests and performed ECG and Holter recordings (starting before the session and

The following dialysis regimen was prescribed: Integra® monitor (Novacor, Rueil-Malmaison, France), AN69 dialyser (Nephral® 500, Hospal), blood flow 300-350 mL/min, dialysate flow 500 ml/min and sodium bicarbonate reinfusion rate 167 mmol/L from 2100 to 2300 mL/h. The dialysate with constant K+ was 2 mmol/L, while potassium profiling was

Both techniques were found to be easy to use, safe and without complications. There were no special technical requirements, and the procedures were well accepted by the nursing personnel. Patient haemodynamic tolerance was good with both techniques, with no

The pre- and post-dialysis results were similar with both techniques. We only observed a difference in blood K+ determined half-way through the dialysis session, with higher values

The ECG parameters in turn showed a significant difference in QTc (QT corrected for heart rate) after dialysis between the two techniques, with better results for AFB-K (448.8 24.2 ms

The mean PVC in the Holter recording was lower with AFB-K (163.5 range 21-900) versus AFB (444.5, range 23-13,565), though statistical significance was not reached (p=0.06)

PVCs proved less severe (Lown grades I-II) with the AFB-K technique than with AFB

All these findings were more obvious in patients with higher blood K+ values at the start

In summary, K+ decreased more slowly with AFB-K than with AFB, and a tendency towards decreased PVCs and their severity was noted (statistical significance probably not being reached because of the limited sample size), as well as a susceptibility to QTc reduction. All this is indicative of fewer arrhythmias. Our findings are similar to those previously reported

in the AFB-K group (4.0 mmol/L) than with AFB (3.6 mmol/L) (P<0.0001).

by other authors (Santoro et al., 2002, Severi et al., 2003, Santoro et al., 2008).

study concluded that the slow clearance of K+ may exert a protective effect.

**6. Our study** 

(n=2).

additional dialysis procedure in our Unit.

continuing until the next session).

3.2-4 mmol/L ingoing and 1-1.3 mmol/L outgoing.

differences in blood pressure or heart rate.

vs 456.8 24 ms, p=0.039).

involving constant K+ (grades I-V).

(Figure 3).

of dialysis.

et al., 1999, Floccari et al., 2004) and onset of paroxysmal atrial fibrillation have been described.

Acetate Free Biofiltration with Potassium Profiled Dialysate (AFB-K) is a haemodialysis technique that attempts to obviate this problem, avoiding sudden potassium reductions during the haemodialysis session, but with due correction of the hyperkalaemia of the patients (Santoro et al., 2005).
