BACKGROUND: The main hypothesis of this study is that patients having regular conventional haemodialysis (HD) will have a smaller decline in cardiac systolic function by using cooler dialysate. Cooler dialysate may also be beneficial for brain function. METHODS/DESIGN: The trial is a multicentre, prospective, randomised, un-blinded, controlled trial. Patients will be randomised 1:1 to use a dialysate temperature of 37 degrees C for 12 months or an individualised cooled dialysate. The latter will be set at 0.5 degrees C less than the patient's own temperature, determined from the mean of 6 prior treatment sessions with a tympanic thermometer, up to a maximum of 36 degrees C. Protocol adherence will be regularly checked. Inclusion criteria are incident adult HD patients within 180 days of commencing in-centre treatment 3 times per week with capacity to consent for the trial and without contra-indications for magnetic resonance imaging. Exclusion criteria include not meeting inclusion criteria, inability to tolerate magnetic resonance imaging and New York Heart Association Grade IV heart failure. During the study period, resting cardiac and cerebral magnetic resonance imaging will be performed at baseline and 12 months on an inter-dialytic day. Cardiovascular performance during HD will also be assessed by continuous cardiac output monitors, intra-dialytic echocardiography and biomarkers at baseline and 12 months. The primary outcome measure is a 5% between-group difference in left ventricular ejection fraction measured by cardiac magnetic resonance imaging at 12 months compared to baseline. Analysis will be by intention-to-treat. Secondary outcome measures will include changes in cerebral microstructure and changes in cardiovascular performance during HD. A total of 73 patients have been recruited into the trial from four UK centres. The trial is funded by a Research for Patient Benefit Grant from the National Institute of Healthcare Research. AO is funded by a British Heart Foundation Clinical Research Training Fellowship Grant. The funders had no role in the design of the study. DISCUSSION: This investigator-initiated study has been designed to provide evidence to help nephrologists determine the optimal dialysate temperature for preserving cardiac and cerebral function in HD patients. TRIAL REGISTRATION: ISRCTN00206012 and UKCRN ID 7422. ; Odudu, Aghogho Eldehni, Mohamed Tarek Fakis, Apostolos McIntyre, Christopher William eng British Heart Foundation/United Kingdom Multicenter Study Randomized Controlled Trial Research Support, N.I.H., Extramural Research Support, Non-U.S. Gov't England 2012/06/23 06:00 BMC Nephrol. 2012 Jun 21;13:45. doi: 10.1186/1471-2369-13-45.