Sodium profiling, but not cool dialysate, increases the absolute plasma refill rate during hemodialysis

Intradialytic hypotension is often caused by a discrepancy between ultrafiltration and plasma refilling. Increasing the plasma refill rate could therefore reduce intradialytic hypotension. We used a recently developed method to measure the effect of cool dialysate and sodium (Na) profiling on refill during hemodialysis (HD). Using a Gambro AK200 with blood volume (BV) sensor plus computer-guided external pump, a high ultrafiltration rate quickly induced a preset BV reduction. A software feedback mechanism subsequently adjusted the ultrafiltration rate continuously to maintain BV between very narrow preset boundaries. The continuously changing, software-generated ultrafiltration rate then quantitatively equalled refill. Absolute plasma refill rate was measured in six stable patients without intradialytic hypotension, undergoing HD without intervention, with cool dialysate (1 degrees C below core temperature), and with Na profiling (gradually declining from 150 to 140 mmol/l). Baseline refill rate was 20.1 + or - 4.0 ml/min (mean + or - SD). Although cool dialysate did not affect refill (22.2 + or - 4.1 ml/min, p = 0.27 vs. baseline), Na profiling induced a significant improvement (26.8 + or - 3.7 ml/min, p = 0.006 vs. baseline). Using our method to measure absolute plasma refill rate during HD, we demonstrated that Na profiling indeed improves the plasma refill rate. A potential effect of cool dialysate could not be established.