Consequences of overhydration and the need for dry weight assessment

Despite significant progress in the fields of dialysis technology and medical therapy, mortality of hemodialysis (HD) patients remains high. Chronic overhydration is a major contributor to the high cardiovascular morbidity and mortality observed in HD patients. The difficulty of measuring excess fluid accurately and the determination of 'dry weight' are reflected in the abundant literature on overhydration. Data indicate that a significant proportion of HD patients are not at 'dry weight'. Considering its impact on cardiovascular diseases, the relation between excess fluid, sodium, interdialytic weight gain, hypertension and cardiac diseases needs more attention. Clearly the reduction of sodium intake is of prime importance. This can be achieved by a reduction of dietary sodium intake, individualized dialysate sodium concentration, avoidance of sodium profiling and use of hypertonic saline during dialysis. These measures are expected to result in less thirst and consecutive water intake, thereby facilitating achieving dry weight (DW). In concert, the application of new tools for DW assessment such as continuous intradialytic bioimpedance spectroscopy measurement, means to prevent intradialytic symptoms (e.g. glucose bolus instead of hypertonic saline; improved hemodynamic stability by reduced dialysate temperature) may be operative in reducing morbidity and mortality in HD patients.