**6. Our study**

230 Technical Problems in Patients on Hemodialysis

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

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

One of the first studies on potassium profiled haemodialysis was published by Readelli (Readelli et al., 1996). This multicenter, randomised, cross-over, prospective study evaluated 42 patients with a known increase in Premature Ventricular Complexes (PVC) during dialysis (Holter-ECG recording). The author compared a haemodialysis model with constant K+ in the dialysate versus a model with decreasing K+ that maintained a constant K+ gradient between the blood and dialysate. A significant reduction of over 30% in PVC was recorded (both in terms of the number of PVC/h and as regards the PVC couplets/h) when performing potassium profiled dialysis. This PVC decrease is observed particularly in the first hour of dialysis, which corresponds to the greatest reduction in blood K+ values in the case of dialysis with constant K+. The result is obtained without affecting the K+ levels

Subsequently, Santoro (Santoro et al., 2002) published a study including 125 patients from a single centre in which dialysis with two techniques – one comprising AFB with constant K+ and another with potassium profiled dialysate (AFB-K) – resulted in slower K+ reduction with the latter technique (serum K+ being greater in the first hour of dialysis with the potassium profiling procedure). Both techniques reached the same final serum K+ levels. This study recorded a reduction in the number of intra-dialysis arrhythmias, particularly in those patients with a significant presence of ventricular ectopic beats. In conclusion, the safety and easy application of the AFT-K technique was confirmed, as well as the possibility of adapting the profile to each individual patient. In addition, this treatment was shown to reduce the impact upon repolarisation homogeneity and thus

Buemi et al. (Buemi et al., 2005) studied a series of 28 patients undergoing haemodiafiltration with constant K+ (HDF), compared with HDF involving variable K (HDFK). The authors examined the ECG tracings at different times during dialysis to measure the QT-interval, and analysed serum K, intra-erythrocyte K and the electrical membrane potential at rest. Intra-erythrocyte K remained constant. The electrical membrane potential at rest decreased over time, though the reduction proved significantly greater in HDF versus HDFK. In turn, the ECG tracing showed a reduction in QT dispersion and in the QT-interval with HDFK. The authors concluded that the risk of arrhythmia may be

Subsequently, Santoro (Santoro et al., 2008) published a multicenter, randomised, crossover, prospective study in which 30 patients susceptible to arrhythmia were dialysed in a cross-over design with AFB involving constant K+ (2.5 mEq/L) or AFB with decreasing K in the dialysate bath (AFB-K). A tendency towards fewer arrhythmias is observed with AFB-K that becomes significant in the case of patients sensitive to dialysis. A reduction in the number of PVC per hour is observed both during dialysis and hours after the end of dialysis (with a maximum reduction in the number of PVC 14 hours after dialysis). In the first hour

described.

patients (Santoro et al., 2005).

**5. Development of AFB-K** 

prevent cardiac arrhythmia.

compared with conventional constant K+ haemodialysis.

lower when using haemodialysis with variable K.

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 additional dialysis procedure in our Unit.

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 (n=2).

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 continuing until the next session).

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

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 differences in blood pressure or heart rate.

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

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 vs 456.8 24 ms, p=0.039).

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) (Figure 3).

PVCs proved less severe (Lown grades I-II) with the AFB-K technique than with AFB involving constant K+ (grades I-V).

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

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

Acetate Free Biofiltration with Potassium Profiled Dialysate (AFB-K) 233

Unit or of the attending nephrologists, since it is very simple to prescribe, and likewise does not pose an added workload for the nursing personnel, since the technique is simple and

One of the advantages afforded by this technology is the possibility of individualising the prescription of dialysis with a view to improving patient tolerability and prognosis (Phipps et al., 2010). Potassium profiling of the dialysate with AFB-K allows us to advance in this direction. The reduction of arrhythmias and the improved haemodynamic stability can contribute to improve the cardiovascular prognosis and survival of the patients. Larger studies (which are also more difficult to carry out) are needed to confirm improved patient

Cupisti A, Galetta F, Caprioli R et al. Potassium removal increases the QTc interval

Santoro A, Mancini E, Fontanazzi F, Paolini F, Potassium profiling in acetate-free

Santoro A, Guarnieri F, Ferramosca E, Grandi F. Acetate Free Biofiltration Contrib Nephrol

Cavalcanti S, Ciandrini A, Severi S, et al. Model-based study of the effects of the

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Santoro A, Mancini E, Gaggi R, et al. Electrophysiological response to dialysis: the role of dialysate potassium content and profiling. Contrib Nephrol 2005; 149: 295-305 Redaelli B., Locatelli F., Limido D., et al. Effect of a new model of haemodialysis potassium removal on the control of ventricular arrhythmias. Kidney Int. 1996 (5): 609-617. Buemi M, Aloisi E, Coppolino G, et al. The effect of two different protocols of potassium haemodiafiltration on QT dispersion. Nephrol Dial Transplant 2005; 20: 1148-1154 Santoro A, Mancini E, London G, et al. Patients with complex arrhythmias during and after

haemodialysis suffer from different regimens of potassium removal. Nephrol Dial

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easy to schedule.

**9. Conclusions** 

**10. References** 

survival with the new, attractive dialysis techniques.

2007, vol 158: 138-152.

2004; 65: 1499-1510.

Fig. 3. PVC/24 h with both techniques (AFB and AFB-K).

In view of the results obtained, we decided to incorporate the technique to our Unit. We have indicated AFB-K in 27 patients who have been on dialysis for up to 5 years with the same technique.

We concluded that patients with arrhythmia or at risk of suffering arrhythmia benefited from potassium profiled dialysis, particularly those subjects with hyperkalaemia. Larger studies are required to confirm this reduction in arrhythmias, which could imply improved survival for patients with such a high cardiovascular risk.
