[Thermal energy balance during hemodialysis: the role of the filter membrane].
BACKGROUND
Body temperature tends to increase during conventional haemodialysis; this might interfere with normal cardiovascular response to dialytic ultrafiltration, thus facilitating the occurrence of symptomatic hypotension. Putative factors responsible for changes in thermal balance during haemodialysis include heat load from the dialysis bath, reduction in convective heat loss secondary to skin vessel vasoconstriction, heat overproduction due to central stimulation by bioincompatibility reactions to the filter membranes. The aim of the present study was twofold: to define thermal energy balance (ET) during dialysis and to investigate the effect of membrane bioincompatibility on energy balance


METHODS
We measured ET in 12 patients (9M, 3F) during two identical dialysis sessions, differing only in the membrane composition of the filters used: cuprophane 1.3- 1.6 mq and LF polysulphone 1.3- 1.6 mq. Thermal energy balance studies were performed by the Blood Temperature Monitor (Fresenius Medical Care) under conditions in which the core temperature of the patients was maintained unchanged from the start to the end of the dialysis procedure.


RESULTS
Arterial blood temperatures were constant, while dialysate and venous blood temperatures progressively decreased (from 36.9 to 35.4 C and from 36.5 to 35.1 C for cuprophane; from 36.9 to 35.2 and from 36.9 to 35.1 for polysulphone membrane). Mean thermal energy transfer was negative (removal of energy from the patients to the extracorporeal circuit) with both filters, equal to 146 KJ with cuprophane and to 163 KJ with polysulphone. When a stepwise multiregression analysis was applied, hourly energy transfer (ET) was significantly and independently correlated with both ultrafiltration rate (UF=% b.w.) and heart rate changes (HR) according to the equation: ET= -92.03+41.29 UF+1.04 HR (p<0.0003). Conclusions. In this study we present experimental evidence that increased body temperature during dialysis is not caused by heat load from the dialysis bath, nor by heat over production secondary to bioincompatibility reactions. Consequently, haemodynamic responses to dialytic ultrafiltration may be regarded as the main regulatory factor of thermal balance.
D000368:Aged; D000369:Aged, 80 and over; D001672:Biocompatible Materials / Q000737:chemistry; D001831:Body Temperature; D002482:Cellulose / Q000031:analogs & derivatives* / Q000737:chemistry; D018481:Convection; D004734:Energy Metabolism; D005260:Female; D005334:Fever / Q000209:etiology; D006439:Hemodynamics; D006358:Hot Temperature; D006801:Humans; D007676:Kidney Failure, Chronic / Q000150:complications / Q000503:physiopathology / Q000628:therapy; D008297:Male; D008567:Membranes, Artificial; D008875:Middle Aged; D011108:Polymers / Q000737:chemistry; D006435:Renal Dialysis / Q000009:adverse effects / Q000295:instrumentation; D013450:Sulfones / Q000737:chemistry; D013696:Temperature
D001672:Biocompatible Materials; D008567:Membranes, Artificial; D011108:Polymers; D013450:Sulfones; C017662:polysulfone P 1700; D002482:Cellulose; C009865:cuprammonium cellulose
Studio del bilancio termico durante la dialisi: ruolo svolto dalla membrana dei filtri.