Vascular reactivity during haemodialysis and isolated ultrafiltration: thermal influences

Abstract

Background: The present study was performed to assess the role of the extracorporeal blood temperature in the disparate cardiovascular response between isolated ultrafiltration and combined ultrafiltration-haemodialysis.

Methods: In twelve stable dialysis patients (21-77 years), blood pressure and heart rate (Finapres) as well as forearm vascular resistance and venous tone (strain-gauge plethysmography) were measured during 1-h isolated ultrafiltration and 1-h combined ultrafiltration-haemodialysis (bicarbonate, sodium 141 mmol/l) at a fixed ultrafiltration rate of 0.91 l/h. The sequence of both treatment modalities was randomly defined within each patient. Serving as his or her own control, each patient was studied at two different dialysate temperatures: 37.5 and 35.0 degrees C.

Results: At a dialysate temperature of 35.0 degrees C extracorporeal blood cooling during combined ultrafiltration-haemodialysis was comparable to isolated ultrafiltration. The cardiovascular response in isolated ultrafiltration was characterized by a significant increase in both forearm vascular resistance and venous tone, while heart rate even decreased. As a result, blood pressure remained unchanged or even increased. In contrast, during combined ultrafiltration-haemodialysis at a dialysate temperature of 37.5 degrees C the increase in forearm vascular resistance was only small and insignificant, while venous tone decreased significantly. Heart rate tended to increase. Combined ultrafiltration-haemodialysis at a dialysate temperature of 35.0 degrees C was also associated with a small increase in forearm vascular resistance. However, venous tone remained stable while heart rate decreased. At both dialysate temperatures, blood pressure was well maintained.

Conclusions: We conclude that differences in cardiovascular reactivity between isolated ultrafiltration and combined ultrafiltration-haemodialysis are only partially explained by differences in the extracorporeal blood temperature. In addition, especially venous reactivity is improved by lowering the dialysate temperature.