ASSESSMENT OF POSTDIALYSIS DRY-WEIGHT - A COMPARISON OF TECHNIQUES

Because clinical indices of hydration state are insensitive, the estim ation of correct postdialysis dry weight is still a major problem. Rec ently, some new techniques have been introduced to assess postdialysis dry weight more accurately. The plasma concentrations of the biochemi cal markers atrial natriuretic peptide (ANP) and cGMP are related to i ntravascular hydration state. The echographically measured inferior ca val vein diameter (VCD) is linked to right atrial pressure and blood v olume (BV). Regional noninvasive conductivity measurements provide inf ormation about regional extracellular-fluid volume (EFV). In this stud y of postdialysis ANP and cGMP concentrations, VCD and EFV yielded pos tdialysis diagnoses of hydration state in 18 patients on maintenance d ialysis. In order to verify the established diagnosis, hemodynamic and BV changes during dialysis were studied. In postdialysis underhydrate d patients, differentiated according to VCD and EFV standards, a prono unced decrease in BV, stroke volume, and left ventricular end-diastoli c diameter compared with postdialysis normohydrated patients was obser ved. Hemodynamic and BV changes during dialysis were identical in the groups selected according to postdialysis ANP level. Only a difference in BV decrease was demonstrated between the groups selected according to postdialysis cGMP. Predialysis and postdialysis VCD correlated wel l with the corresponding EFV (r = 0.7 and r = 0.8, respectively). Beca use VCD and EFV were related and interpretation yielded diagnoses of p ostdialysis hydration state that were substantiated by the finding of classical hemodynamic features of underhydration, both are an asset in the diagnosis of postdialysis dry weight. cGMP values are less inform ative, and ANP does not provide any information at all.