On-line technique for producing substitution fluid in haemodiafiltration and haemofiltration.

Abstract

When the kidneys are not able to fulfil their task anymore the individual reaches a situation known as End-Stage Renal Disease (ESRD). Haemodialysis may be carried out. In order to have a more efficient dialysis the treatment modes haemodiafiltration and haemofiltration are also in use. In these modes a substitution fluid is added to the bloodstream and continuously removed by the dialyser. However, these modes require large volumes of sterile fluids, 10 to 30 litres for haemodiafiltration and 70 - 100 litres for haemofiltration. This fact has made these treatment modes expensive. The fluids have traditionally been produced by the pharmaceutical industry in five litre bags, but in bags not all solutions are stable or possible to produce, for instance when sodium bicarbonate is used as a buffer. Today sodium bicarbonate is the absolute predominant buffer. An alternative way of producing the fluids has to be found. In 1978 LW Henderson (1) described a technique using filtration to produce substitution fluid on-line i.e. preparing the fluid directly on site and giving it to the patient. Since then work has taken place in order to construct a system that is able to both mix, sterilise and administrate the substitution fluid in haemodiafiltration and haemofiltration. This work has resulted in dialysis machines with the feature to fulfil the task of producing sterile substitution fluid. On-line haemodiafiltration is carried out in dialysis clinics. There are approximately 65 in Sweden, 1000 in Germany, 900 in Italy, 600 in France and 2500 in the US. The number of dialysis patients is around 1.000.000 worldwide and the increase is around 7 - 9% annually.