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

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Abstract
Background. Haemodynamic stability is better maintained during isolated ultrafiltration (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 energy 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 Td of 35.5°C and UF+HD at Td of 37.5°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 particular patient during i-UF in the first part of the study. Results. First part of the study: body temperature (BT) decreased significantly during i-UF (−0.25±0.25°C, PPPPPPP=not significant). Second part of the study: there was a slight, but not significant, decrease in BT during UF+HD ET-set (−0.17±0.26°C). The changes in BT did not differ significantly between i-UF and UF+HD ET-set. After 1 h of UF+HD ET-set, the mean Td was 34.75°C (34.0–36.0°C). The correlation between pre-dialysis BT and Td during UF+HD ET-set was significant (r=0.764, PConclusion. ET gives a more negative value during i-UF than during UF+HD 35.5°C and than during UF+HD 37.5°C. To obtain the same thermal ET during UF+HD as that achieved during i-UF, a mean Td of 34.75°C is needed, depending on the pre-dialytic BT of the patient. The results of this study may be of relevance in relation to future clinical investigations which can elucidate whether differences in vascular response between i-UF and UF+HD are only related to differences in thermal balance.