INTRODUCTION The attention of the nephrological community is current- ly focused on reducing overall morbidity and mortality in dialysis patients. It is well known that both hypertension and hypotension, mainly caused by dialytic sodium re- moval, are the most important factors in determining car- diovascular morbidity, and that cardiovascular disease is undoubtedly the main cause of mortality in dialysis patients (1,2). Increasing the sodium dialysate concen- tration is an effective means of reducing intradialytic hypo- tension, along with the other adverse effects of sodium depletion (3,4). Nevertheless, if the sodium removal is insufficient, it inevitably leads to overhydration and serious adverse cardiovascular effects: pulmonary edema, hyper- tension, myocardial hypertrophy and thereafter dilatation. On the other hand, according to the main conclusion of the American National Cooperative Dialysis Study (NCDS), patient morbidity and treatment failure are related to the dialysis “dose” defined by Kt/V (5). Moreover, it has recently been shown that there is a 7% reduction in the risk of mortality for every 0.1 increase in delivered Kt/V up to 1.3 (6). It is therefore essential to be able to quantify both the prescribed and particularly the delivered dialysis “dose”, since there is often a great difference between the two (7-9). The dialysate sodium concentration required to match interdialytic sodium loading and intradialytic sodium re- moval can only be computed using one of a number of mathematical models (10-13). However, these models are unsuitable for routine clinical application, because the required blood sampling and parameter measurements or estimates are very demanding for the medical and nursing staff. Direct quantification of removed urea, which allows the most reliable calculation of urea distribution volume (V), could be the gold standard for the determination of Artificial Kidney and Dialysis The International Journal of Artificial Organs / Vol. 21 / no. 9, 1998 / pp. 521-525 Conductivity: on-line monitoring of dialysis adequacy L. DEL VECCHIO, S. DI FILIPPO, S. ANDRULLI, C. MANZONI, M. CORTI, F. BARBISONI, F. LOCATELLI Department of Nephrology and Dialysis, Lecco Hospital, Lecco - Italy © by Wichtig Editore, 1998 0391-3988/521-05 $02.50/0 ABSTRACT: Cardiovascular disease and the inadequacy of delivered dialysis are the main factors determining morbidity and mortality in dialysis patients. We have already demonstrated that a con- ductivity kinetic model makes it possible to match interdialytic sodium loading and intradialytic sodium removal (the main factor determining cardiovascular morbidity) without the need for blood samples and, thus, in routine clinical practice. The aim of the present study was to test the possibility of using the conductivity method also to deter- mine Kt/v without blood or dialysate sampling. In 18 steady-state patients, the urea distribution volume (V) was kinetically determined once using ionic dialysance (D) values instead of those of effective urea clearance. One month later, the Kt/V was determined by using the current D and T values and the predetermined V (Dt/V), then compared with the equilibrated Kt/V computed by means of the SPVV kinetic model (eqKt/V). The mean value of Dt/V was 1.18 ± 0.15; while of eqKt/V it was 1.18 ± 0.16, with a mean difference of 0.00 ± 0.07. The conductivity method therefore seems to be very promising not only for monitoring the sodium balance, but also for quantifying delivered dialysis. Since its simplicity and low-cost make it suitable for use at each dialysis session, the conductivity method could therefore lead to significant progress in dialytic practice by contributing to the elimination of the two main causes of morbidity and mortality in dialysis patients. (Int J Artif Organs 1998; 8: 521-5) KEY WORDS:Kt/V, Hydro-sodium balance, Conductivity, Ionic dialysance DEL VECCHIO 521 3-11-1998 16:36 Pagina 521