Adequacy in pre-dilution haemofiltration: Kt/V or infusion volume?

Kt/V is the main index of adequacy for diffusive and diffusive-convective m ethods of extracorporeal depuration, yet there exists no universally accept able validation of an adequacy index for the solely convective methods such as haemofiltration (HF). The aim of the present study is to analyse which of the parameters of adequacy used in two multicentre HF studies, Kt/V for urea or infusion volume, correlate best with nutritional parameters and can therefore be utilized for the evaluation of treatment dose in on-line pre- dilution HF. Twenty-three clinically stable patients were enrolled in the first study [3 months of haemodialysis (HD) + 3 months of HF]. In the second study, 24 st able patients were studied in three phases: 6 months in HF, 6 months in HD and a further 6 months in HF; in this study, a target of Kt/V=1.2 in all th ree periods was pre-established: 15 patients completed the full study. In b oth studies, we utilized the same monitor (AK 100/200 Ultra, Gambro), the s ame membrane (poly amide) and the same on-line prepared ultrapure dialysis fluid and sterile infusion solution. In both studies. we ensured that HF fulfilled the following parameters of a dequacy: urea kinetics, cardiovascular and blood pressure stability (better in HF than in HD), common haematochemical and nutritional parameters, redu ction in beta(2)-microglobulin levels, a good intra- and extra-session clin ical outcome, and a good quality Of life with morbidity and mortality rates no different from those of HD. HF proved to be an efficacious method of ensuring adequate depuration and a good quality of life for uraemic patients. We have shown that in longer pe riods of HF, a notable correlation between Kt/V and normalized protein cata bolic rate (nPCR) and an equally good correlation between total ultrafiltra tion (UF)/dry weight ratio and nPCR could be achieved. In both studies. the patients showed a good level of epuration adequacy when total UF per sessi on was at least 1.3 times the dry body weight. The total UF/body weight rat io thus seems to be an easy method in HF because of its greater ease of pre dictability and measurement, also when it is used independently of the Kt/V index.