Isothermic hemodialysis and ultrafiltration

The increase in patient temperature during hemodialysis is explained by hem odynamic compensation during ultrafiltration and hypovolemia that leads to peripheral vasoconstriction and reduced heat losses. We analyzed 51 stable high-efficiency hemodialysis treatments in 27 patients during isothermic di alysis in which body temperature was maintained at a constant level (+/- 0. 1 degrees C) using the temperature-control option of the Blood Temperature Monitor (BTM; Fresenius Medical Care, Bad Homburg, Germany). Hemodialysis w as delivered using ultrapure water (limulus amebocyte lysate test < 0.06 en dotoxin units/mL) at mean blood flows of 410 +/- 40 mL/min. During treatmen ts lasting 178 +/- 23 minutes, 4.8% +/- 1.4% of postdialysis body weight (W %) and 9.5% +/- 2.5% of postdialysis body water were removed using mean ult rafiltration rates of 1.1 +/- 0.3 L/h, Dialysate temperatures significantly decreased from 35.9 degrees C +/- 0.3 degrees C to 35.6 degrees C +/- 0.6 degrees C during hemodialysis. During these treatments, 187 +/- 69 kJ of th ermal energy were removed from the patients through the extracorporeal circ ulation using cool dialysate. Extracorporeal heat flow was 17 +/- 6 W. Ener gy expenditure (H) estimated from anthropometric data was 65 +/- 12 W. Thus , 28% +/- 10% of estimated energy expenditure (H%) was removed during isoth ermic dialysis. A highly significant correlation was observed between H% an d W% (H% = -5.6 * W%; r(2) = 0.91; P < 0.0001). This result Is in support o f the volume hypothesis of intradialytic heat accumulation and provides a r ule of thumb to estimate extracorporeal cooling requirements for isothermic dialysis. Approximately 6% of H must be removed through the extracorporeal circulation for each percent of ultrafiltration-induced body-weight change . The importance of body temperature control during hemodialysis increases with increased ultrafiltration requirements. (C) 2000 by the National Kidne y Foundation, Inc.