[Role of sodium in the control of compartmental distribution of water during hemodialysis. I. Measurement of water transfer].

Symptomatic hypotension and other symptoms of the so-called dialytic desiquilibrium syndrome have been related to alterations of body fluid osmolality and distribution. Fluid removal from the intracellular compartment can be achieved by manipulating the sodium dialysate (NaD). The extracellular fluid volume ( EFCV ) was measured with inulin and/or 35SO = 4. Total body water changes were calculated in terms of fluid substraction induced by dialysis. They were monitored in 12 patients on hemodialysis with a highly permeable membrane and a careful monitoring of ultrafiltration. NaD was maintained constant throughout the session and was comprised between 140 and 170 mmol/l. Below 150 mmol/l NaD, ECFV was reduced more than the weight loss, indicating concomitant intracellular water loading. Conversely, over 150 mmol/l NaD weight loss resulted from extracellular and cellular water. We conclude: 1) transcellular water shift during dialysis is dependent of sodium dialysate; 2) net cellular water-shift was obtained for NaD higher than 150 mmol/l; 3) at least two compartments for water distribution should be taken into account for sodium modeling.