Effects of body core temperature reduction on haemodynamic stability and haemodialysis efficacy at constant ultrafiltration

Intradialytic body temperature changes are governedby the thermal energy balance and heat capacity ofthe body. Resting energy expenditure is dissipated tothe environment by evaporation, conduction and radi-ation. Homeostatic mechanisms maintain body tem-perature to an individual set-point by changing theradiative heat loss through vasoconstriction andvasodilatation.During haemodialysis, the extracorporeal circuit hasa great effect on intradialytic thermal energy balance.The dialyser is a nearly perfect heat exchanger, wherebyblood leaves the dialyser at thermal equilibrium withdialysate. The energy balance in the dialyser is afunction of the difference between arterial blood tem-perature and dialysate temperature as influenced byextracorporeal blood flow and the specific heat anddensity of blood. Additional effects on intradialyticthermal energy balance come from energy loss in thevenous blood line which is dependent on blood-envi-ronment temperature differences. Recently a bloodtemperature monitor (Fresenius AG, Bad Homburg,Germany) has become available that allows continuousmonitoring of thermal energy balance and feedbackcontrol of body temperatur [1]e . This is a non-invasivedevice by which blood temperature is measured in thearterial and venous blood line. The measured arterialand venous temperatures are corrected for temperaturereduction between the sensor heads and the dialysisaccess. From the differences between these temper-atures, blood flow and heat capacity of blood, thermalenergy balance in the patient is calculated as