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 i n 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 degrees C) versus two war m (37.5 degrees C) dialysate treatments. The % change in mean arterial pressure was different when using the cool (+6.5 +/- 9.7 mm Hg) versu s the warm (-13.4 +/- 3.6) dialysate (P < 0.01), despite comparable am ounts of fluid removal. Percent changes in cardiac output were similar with the two dialysates, and thus the blood pressure effect was due p rimarily to changes in total peripheral resistance (%Delta TPR, 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 degrees C, wh ereas body temperature increased by 0.52 +/- 0.14 degrees C during use of warm dialysate. Measured urea recovery normalized to the predialys is urea nitrogen concentration was similar with the two treatments: co ol 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 afte r 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 alteratio n in hemodynamics has no clinically important effects on either the am ount of urea removal or the extent of post-dialysis urea rebound.