**3. Description of the AFB-K technique**

Acetate Free Biofiltration with Potassium Profiled Dialysate (AFB-K) is the same haemodiafiltration technique free from acetate as that described above, with the addition of a potassium profiled dialysate. This is achieved with a double bag of concentrate (Santoro et al., 2002) – one bag with potassium and the other without it (Figure 2).

The dialysis machine takes concentrate from one bag or the other to form a potassium profiled dialysate: high at the start of dialysis and low at the end. The initial and final K+ values of the dialysate are established individually for each patient (e.g., 4 mmol/L at the start of dialysis and 1 mmol/L at the end), according to a series of guidelines supplied by the manufacturer, and based on the needs of each patient. The aim is to maintain a constant K+ gradient between the blood and dialysate bath, in order to prevent sudden K+ reductions (Santoro et al., 2002).

The slow decrease in K+ during dialysis is added to the advantages inherent to AFB. Dialysis with high K content in the dialysate cannot adequately reduce patient hyperkalaemia,

permeable biocompatible membranes). These advantages prove more evident in patients susceptible to suffering hypotension during dialysis, such as diabetics or elderly subjects with autonomous nervous system disorders, heart disease or liver disease, and subjects with significant comorbidity (Tsutomu et al., 2011, Sato et al., 2011). In a literature review, Santoro et al. (Santoro., 2007) described a reduction in hypotension events in AFB vs bicarbonate haemodialysis: the probability of intradialysis hypotension with AFB was reported to be close to 40% of the probability of intradialysis hypotension in the case of

**Blood entry Blood entry**

**Dialisate**

**exit**

**Dialisate Dialisat**

Na Ca K Mg

Ca K Mg

+ ++ + ++

**Dialisate without tampon**

**Dialisate without tampon**Na

Cl-

Cl -

H 2

H

CONC.

CONC.

GLUCOSE H2 O

GLUCOSE H2O

Acetate Free Biofiltration with Potassium Profiled Dialysate (AFB-K) is the same haemodiafiltration technique free from acetate as that described above, with the addition of a potassium profiled dialysate. This is achieved with a double bag of concentrate (Santoro et

The dialysis machine takes concentrate from one bag or the other to form a potassium profiled dialysate: high at the start of dialysis and low at the end. The initial and final K+ values of the dialysate are established individually for each patient (e.g., 4 mmol/L at the start of dialysis and 1 mmol/L at the end), according to a series of guidelines supplied by the manufacturer, and based on the needs of each patient. The aim is to maintain a constant K+ gradient between the blood and dialysate bath, in order to prevent sudden K+ reductions

The slow decrease in K+ during dialysis is added to the advantages inherent to AFB. Dialysis with high K content in the dialysate cannot adequately reduce patient hyperkalaemia,

al., 2002) – one bag with potassium and the other without it (Figure 2).

**Blood exit Blood exit**

conventional bicarbonate haemodialysis.

**Na <sup>+</sup> HCO <sup>3</sup>**

**Infusion Infusion**

**-**

Fig. 1. AFB dialysis circuit.

**Patient**

**Patient**

(Santoro et al., 2002).

**3. Description of the AFB-K technique** 

though symptomatically it is very well tolerated. Dialysis with low K content in the dialysate adequately reduces patient hyperkalaemia, but proves highly arrhythmogenic and is poorly tolerated by the patients. With AFB-K we are able to adequately reduce hyperkalaemia without causing arrhythmia, since blood K is gradually reduced. The patients who stand to benefit most from this dialysis technique are those with significant comorbidity and therefore with an increased risk of suffering arrhythmia.

Fig. 2. AFB-K dialysis circuit.
