Thermal energy balance and body temperature: comparison between isolated ultrafiltration and haemodialysis at different dialysate temperatures

Background. Haemodynamic stability is better maintained during isolated ult rafiltration (i-UF) than during combined ultrafiltration/haemodialysis (UF + HD). This difference might be explained by differences in thermal energy balances. In this study we compared the thermal energy balance of I-UF with UF + HD at different dialysate temperatures (Td) and determined the Td at which the thermal energy balance during UF + HD is similar to the thermal e nergy balance during i-UF. Methods. In the first part of the study, 10 chronic haemodialysis patients were compared during three different treatment sessions, I-UF, UF + HD at T d of 35.5 degrees C and UF + HD at Td of 37.5 degrees C. The second part of the study consisted of one session of 1 h of UF + HD (UF + HD ET-set) with a pre-set energy transfer (ET) at the same level of ET found for that part icular patient during i-UF in the first part of the study. Results. First part of the study: body temperature (BT) decreased significa ntly during i-UF (-0.25+/-0.25 degrees C, P < 0.05) and UF + HD 35.5 degree s C (-0.24+/-0.18 degrees C, P < 0.05) and increased significantly during U F + HD 37.5 degrees C (+0.18+/-0.19 degrees C, P < 0.05). The differences b etween the change in BT during UF + HD 37.5 degrees C compared with the oth er treatments were significant (P < 0.05). ET gave a significantly more neg ative value during i-UF (-30.8+/-3.1 W, P < 0.05) than during UF + HD 35.5 degrees C (-23.6+/-4.1 W, P < 0.05). A slightly positive ET was found durin g UF + HD 37.5 degrees C (+0.4 +/- 4.7 W, P = not significant). Second part of the study: there was a slight, but not significant, decrease in BT duri ng UF + HD ET-set (-0.17+/-0.26 degrees C). The changes in BT did not diffe r significantly between I-UF and UF + HD ET-set. After 1 h of UF + HD ET-se t, the mean Td was 34.75 degrees C (34.0-36.0 degrees C). The correlation b etween pre-dialysis BT and Td during UF + HD ET-set was significant (r = 0. 764, P < 0.05). Conclusion. ET gives a more negative value during i-UF than during UF + HD 35.5 degrees C and than during UF + HD 37.5 degrees C. To obtain the same t hermal ET during UF + HD as that achieved during I-UF, a mean Td of 34.75 d egrees C is needed, depending on the pre-dialytic BT of the patient. The re sults of this study may be of relevance in relation to future clinical inve stigations which can elucidate whether differences in vascular response bet ween I-UF and UF + HD are only related to differences in thermal balance.