Influence of blood temperature on vascular stability during hemodialysis and isolated ultrafiltration.

We tested the hypothesis that differing temperature (T) changes in extracorporeal blood circuit might partly account for the difference in vascular stability (VS) between isolated ultrafiltration (UF) and simultaneous UF-hemodialysis (HD). The study was carried out in 6 patients who presented frequent episodes of symptomatic hypotension during the routine dialytic sessions. During simultaneous UF-HD with dialysate T set at 37.5 degrees C (standard HD), blood reentered the patients with a T of about 2 degrees C higher, whereas during isolated UF (standard UF) 2 degrees C lower, than at its exit. These extracorporeal blood T changes were reciprocated by warming the venous line in isolated UF (warm UF) and by setting the dialysate at 34.5 degrees C in simultaneous UF-HD (cold HD). During warm UF mean arterial pressure (MAP) fell and heart rate (HR) increased nearly as much as during standard HD. Vice versa, during cold HD MAP and HR remained nearly as stable as during standard UF. It is concluded that the T changes in blood flowing through the extracorporeal circuit largely account for the differing VS between isolated UF and simultaneous UF-HD.