Abstract—HD and HDF as hemodialytic therapies normally alter patient’s haemodynamic stability, due to the inflammatory response to extracorporeal blood circuit, producing increment of the core temperature (+1.0 ºC). However, such increase in temperature could be controlled by lowering dialysate’s temperature using two main modalities techniques (isothermic and thermoneural) with different patient’s thermal balance consequences, not yet well studied. In this work, energy expenditure (EE) was measured by indirect calorimetry in a group of 12 patients waiting kidney transplant. In each patient, EE was assessed (as a power generation) during isothermic and thermoneutral modalities as a manner of cross and prospective study (a) at before therapy, (b) during therapy and (c) at the end of the HDF therapy. Wheraeas, power extraction was measured by a BTM (Blood Temperature Monitor from Fresenius Inc) in order to determine power balance in a thermodynamic model of the extracorporeal circuit. The results showed significant differences in the power balance when EE at during therapy was subtracted from the EE at before therapy. Then, EE increments were 32 Kcal/4-hours during isothermic and 3.6 Kcal/4-hours during thermoneutral HDF sessions (p < 0.05). While, BTM totals power extraction was 91 and 16.1 Kcal/4-hours (p<0.05), respectively. Additionally, it was estimated a 12 % of EE/day increment during HDF-isothermic at during therapy stage compared with none significative EE increment during thermoneutral modality. The statistical evidence confirmed the expected hypothesis that both modalities affect in different manner the patient’s EE. Also, we conclude there is no satisfactory data interpretation when the thermodynamic model was applied expecting null balance between EE increment and BTM power extraction. Therefore, these findings force to think there is need of different BTM design and measurement setting with ability to follow dynamic patient’s EE changes with the purpose to achieve a better power balance. I. INTRODUCTION HERMAL effects have a very important impact on patient’s hemodynamic stability during hemodialysis and Manuscript received on April 16, 2008. This work was supported by Universidad Autónoma Metropolitana and Instituto Nacional de Cardiología Ignacio Chávez at Mexico City. M. Cadena, H. Medel and F. Rodríguez are with Universidad Autónoma Metropolitana-Iztapalapa, Departamento de Ingeniería Eléctrica, México D.F. 09340, Phone: +52-555-8502-4569, (e-mail: mcm@xanum.uam.mx). A. Mariscal, P. Flores, M. Franco and H. Perez-Grovas are with Instituto Nacional de Cardiología Ignacio Chávez. Juan Badiando No.1 Tlalpan, Mexico DF (e-mail: perhec@cardiologia.org.mx ). B. Escalante is with Departamento de Procesamiento de Señales, Facultad de Ingeniería, Universidad Nacional Autónoma de México, CU, D. F. Mexico (e-mail: boris@servidor.unam.mx). hemodiafiltration therapies. Dialysate temperature control has been shown to play a relevant role for patient’s intradialytic blood pressure stability [1]. Thus, cold dialysate plus convective dialytic therapy has been used to increase the external heat loss compensation, when patient shows core temperature increments (+1.0 ºC) due to the inflammatory response as a consequence of the hemodialytic therapy itself. Then, the basic idea is to avoid patient’s vasodilatation but controlling blood cooling negative effects such as myocardial contractility and venous tone diminishing together with hypothermia discomfort symptoms increasing [2]. Therefore, hemodynamic instability due to patient’s heat accumulation remains as one of the most difficult medical and technological challenges to solve in hemodialysis (HD) and hemodiafiltration (HDF) therapies. The clinic state of the art uses intradialytic adaptive empirical algorithmic approach to control the solutes and energy transfer over the cartridge-dyalysate circuit. The primary objective, if not the single, has been to govern by hypothesis the genesis of the heat accumulation to avoid the dialysis-related hypotension [3]. Specifically, the set of factors which avoid hypotension are related to the specific HD and HDF prescription such as the mode of patient’s temperature control (isothermic or thermonatural modality), ultrafiltration rate prescription, osmolality control, electrolyte composition control, etc [4]. Others factors which promote the loss of hemodynamic homeostasis have been medically treated such as autonomic nervous dysfunction and cardiac diseases. On the other hand, few and controversial studies have been reported about energy expenditure (EE) during HD and HDF therapies [5]. Increase in EE, as a consequence of the increased heat production, during HDF therapy has been suggested but so far there is no clear evidence of the amount of this and the particular differences of EE during isothermic or thermoneural HDF modalities [6]. Unfortunately, many and historical treatments where HD and HDF therapies prescription have preserved dialysate temperature constant, have not contributed for information about the real energy transfer statistics due to the lack of the appropriate technology. However, since 2003 using a BTM device (Blood Temperature Monitor, Fresenius, Bad Homburg, Germany) the extracorporeal energy transfer can be monitored and controlled so that algorithmically the heat removal can be on-line estimated and it is not longer empirically adjusted [7]. Therefore, one important premise for this work was that simultaneous measurement of extracorporeal heat loss Isothermic vs Thermoneutral Hemodiafiltration Evaluation by indirect Calorimetry Miguel Cadena, Humberto Medel, Fausto Rodrguez, Pedro Flores, Alfonso Mariscal, Martha Franco, Héctor Pérez-Grovas and Boris Escalante T 30th Annual International IEEE EMBS Conference Vancouver, British Columbia, Canada, August 20-24, 2008 978-1-4244-1815-2/08/$25.00 ©2008 IEEE. 719