On-line monitoring and convective treatment modalities: short-term advantages

Despite technological advances in dialysis equipment, the morbidity and quality of life of uraemic patients undergoing regular haemodialytic treatment are still severely affected by acute intradialytic complications possibly related to the treatment itself. Cardiovascular instability still affects >30% of dialytic sessions and, although its pathogenesis is multifactorial, dialysate sodium concentration (and, consequently, intradialytic sodium removal) is one of the main factors affecting intradialytic hypotension. Convective treatment modalities and so-called biocompatible membranes increasingly are recognized as improving acute and particularly chronic dialytic complications because a number of the pathways activated in patients during dialysis with 'bioincompatible' membranes have the potential to produce many side effects.

The main clinical studies are reviewed to highlight the advantages of on-line monitoring and convective modalities on acute intradialytic symptoms.

The conductivity kinetic model has been shown to be a reliable and inexpensive method of matching intradialytic sodium removal and interdialytic load. By applying this model to patients prone to dialysis hypotension, a smaller reduction in intradialytic systolic blood pressure has been observed, without any change in dialysate and reinfusate sodium concentrations or dry body weight. Furthermore, a new model of haemodialysis potassium removal based on a decreasing intradialytic potassium concentration and a constant plasma-dialysate potassium gradient is capable of reducing the arrhythmogenic effect of standard haemodialysis. Despite the proven biological superiority of biocompatible membranes, there is no definitive evidence that membrane biocompatibility and/or flux lead to a decrease in acute intradialytic clinical symptoms.

On-line monitoring of intradialytic sodium removal and the potassium gradient is capable of reducing intradialytic hypotension and the arrhythmogenic effect of haemodialysis, and thus having a considerable clinical impact on acute intradialysis complications. As far as the effects of biocompatibility and/or flux on the incidence of acute intradialytic clinical symptoms are concerned, further trials involving a sicker patient population with higher prevalence of intradialytic hypotension are needed in order to achieve statistical power.