**5. Adequacy indices for steady and non-steady metabolic state**

The change of solute mass in the body during dialysis is due to the generation minus removal, but, in general, one can not assume that the solute removal is equal to the generation during the cycle time (i.e. intra- plus inter-dialysis time), especially in acute renal failure, ARF, patients; thus, even the measurement of removed solute in spent dialysate or filtrate does not necessarily accurately reflect the generated mass. In such cases, the real solute generation rate needs to be estimated using computer simulations for specific patients and dialysis parameters by fitting the theoretical predictions to the solute concentration profile using equation (8) for simulation. The calculation of FSR and ECC should then be based on equations (38) and (36) as it was shown by Debowska et al. (Debowska et al., 2010).
