Effect of dialysate temperature on central hemodynamics and urea kinetics

Effect of dialysate temperature on central hemodynamics and urea kinetics. Use of cool dialysate is associated with increased intradialytic blood pressure, but the hemodynamic mechanism is unknown. Whether changes in dialysate temperature affect muscle blood flow, which may the alter the degree of urea compartmentalization, also is unknown. We measured hemodynamics and blood and dialysate-side urea kinetic indices in nine hemodialysis patients during two cool (35.0°C) versus two warm (37.5°C) dialysate treatments. The % change in mean arterial pressure was different when using the cool (+6.5 ± 9.7 mm Hg) versus the warm (-13.4 ± 3.6) dialysate (P < 0.01), despite comparable amounts of fluid removal. Percent changes in cardiac output were similar with the two dialysates, and thus the blood pressure effect was due primarily to changes in total peripheral resistance (%ΔTPR, cool +26 ± 13.6, warm +8.6 ± 14.5; P < 0.02). During cool dialysate use tympanic membrane temperature changed by -0.51 ± 0.23°C, whereas body temperature increased by 0.52 ± 0.14°C during use of warm dialysate. Measured urea recovery normalized to the predialysis urea nitrogen concentration was similar with the two treatments: cool 31.3 ± 0.039 liter-1; warm 29.7 ± 0.021; P = NS. In a second study, post-dialysis urea rebound values from 15 seconds to 30 minutes, expressed as the percent of the post-dialysis SUN, were similar after the two treatments: cool 11.79 ± 1.4; warm 12.21 ± 2.27, P = NS. The results suggest that increased blood pressure associated with use of cool dialysate is due to an increased TPR, and that this alteration in hemodynamics has no clinically important effects on either the amount of urea removal or the extent of post-dialysis urea rebound