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

Intradialytic body temperature changes are governed by the thermal energy balance and heat capacity of the body. Resting energy expenditure is dissipated to the environment by evaporation, conduction and radiation. Homeostatic mechanisms maintain body temperature to an individual set-point by changing the radiative heat loss through vasoconstriction and vasodilatation. During haemodialysis, the extracorporeal circuit has a great effect on intradialytic thermal energy balance. The dialyser is a nearly perfect heat exchanger, whereby blood leaves the dialyser at thermal equilibrium with dialysate. The energy balance in the dialyser is a function of the difference between arterial blood temperature and dialysate temperature as influenced by extracorporeal blood flow and the specific heat and density of blood. Additional effects on intradialytic thermal energy balance come from energy loss in the venous blood line which is dependent on blood-environment temperature differences. Recently a blood temperature monitor (Fresenius AG, Bad Homburg, Germany) has become available that allows continuous monitoring of thermal energy balance and feedback control of body temperature [1]. This is a non-invasive device by which blood temperature is measured in the arterial and venous blood line. The measured arterial and venous temperatures are corrected for temperature reduction between the sensor heads and the dialysis access. From the differences between these temperatures, blood flow and heat capacity of blood, thermal energy balance in the patient is calculated as