The effect of dialysate temperature on energy transfer during hemodialysis (HD).

Abstract

It is well known that the use of low temperature (T) dialysate can have a positive impact on hemodynamic stability during HD. However, little is known on the energy transfer (ET) from the extracorporeal system to the patient in relation to variations in dialysate T (Tdial). In this study, we assessed ET, body T (Tbody), and blood pressure (BP) during dialysis with normal Tdial (37.5 degrees C) and low Tdial (35.5 degrees C). Nine patients (4 males, 5 females; mean age 68 +/- 10 years) were studied with the patient as his/her own control. Bicarbonate was used as dialysate buffer. Hemophane membranes were used. Dialysis contained <100 CFU/mL. Ultrafiltration volume was comparable between the 2 treatment sessions. ET was assessed by continuous measurement of T in the arterial (Tart) and venous side (Tven) of the extracorporeal system (Fresenius BTM(R)) according to the formula: ET = (Tven - Tart) * blood flow * treatment time * specific thermal capacity (3.64 kJ/kg* degrees C) * blood density (1052 kg/m3). RESULTS: Results: mean+/-SD Tdial 37.5 Tdial 35.5 p Delta Syst BP mmHg -43 +/-21 -22 +/-26 <0.05 Delta Dias BP mmHg -15 +/-10 0 +/-19 0.07 Tbody before HD ( degrees C) 36.7 +/-0.3 36.4 +/-0.6 NS Tbody after HD ( degrees C) 37.2 +/-0.2 36.4 +/-0.3 <0.001 Tven after HD ( degrees C) 36.7 +/-0.1 35.0 +/-0.2 <0. 001 ET (kJ) -86 +/-43 -286 +/-74 <0.001 CONCLUSION: Tbody remained stable during Tdial = 35.5 degrees C despite significant energy loss and increased during Tdial = 37.5 degrees C despite netto ET from the patient to the extracorporeal system. The latter suggests that HD itself leads to intrinsic heat generation in the patient. The removal of this excess heat in combination with the cardiovascular response to maintain Tbody may be responsible for the beneficial hemodynamic effects of low Tdial.