Hemodynamic effects of low versus high dialysate temperature in hemodialysis patients: a single-blinded, randomised, cross-over study

Background Cooling of the dialysate may improve intradialytic hemodynamics. This study compared low dialysate temperature (LDT) of 35°C with high dialysate temperature (HDT) of 37°C (standard) in terms of blood pressure (BP), intradialytic hemodynamics, and orthostatic BP. Methods In a single-blind, randomised, controlled, crossover study fourteen hemodialysis (HD) patients underwent a 4-h HD session with LDT (35°C) or HDT (37°C) separated by a 1- week interval. BP was monitored throughout HD. Intradialytic hemodynamics were assessed with ultrasound dilution technique (Transonic). Orthostatic BP was measured pre- and postHD. Results Ultrafiltration (mean with 95% confidence interval) was similar (LDT: 2.6(2.3;2.9) vs HDT: 2.5(2.0;3.1) liters). Arterial line temperature as a marker of body temperature remained stable with LDT but increased with HDT (mean change LDT: 0.0(-0.2;0.1) vs. HDT: 0.4(0.2;0.6)°C) with a mean between intervention difference of -0.4(-0.6;-0.3)°C. BP remained relatively stable on LDT, whereas HDT caused a significantly larger fall in systolic BP. The mean (± SD) fall in intradialytic systolic BP (PreHD vs. lowest intradialytic) was 20.3 ± 10.5 mmHg (HDT) and 9.6 ± 8.8 mmHg (LDT) with a mean between intervention difference of 10.7(3.2; 17.9) mmHg. LDT caused a significantly lower intradialytic heart rate which by the end of dialysis (after 230 minutes) on average was − 6.6(-13.0;-0.2) beats/min lower than HDT. Overall, the intradialytic hemodynamic response was similar except for a trend towards higher peripheral resistance and central blood volume with LDT. There was a significantly greater fall in orthostatic systolic BP after dialysis compared with preHD, but there was no significant difference between interventions and the frequency of orthostatic hypotension postHD was also similar (HDT: 54% and LDT: 43%; P  = 0.57). Conclusion Cooler vs. standard dialysate temperature resulted in significantly higher intradialytic BP but had no significant impact on orthostatic BP response postHD. Trial registration: The study was registered at ClinicalTrials.gov where the full study protocol is available (NCT05052151). Registration date was 26/08 2021.