VASCULAR REACTIVITY DURING HEMODIALYSIS AND ISOLATED ULTRAFILTRATION - THERMAL INFLUENCES

Background. The present study was performed to assess the role of the extracorporeal blood temperature in the disparate cardiovascular respo nse between isolated ultrafiltration and combined ultrafiltration-haem odialysis. Methods. In twelve stable dialysis patients (21-77 years), blood pressure and heart rate (Finapres) as well as forearm vascular r esistance 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 ultrafiltrat ion rate of 0.91 l/h. The sequence of both treatment modalities was ra ndomly 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 degr ees C extracorporeal blood cooling during combined ultrafiltration-hae modialysis was comparable to isolated ultrafiltration. The cardiovascu lar response in isolated ultrafiltration was characterized by a signif icant increase in both forearm vascular resistance and venous tone, wh ile heart rate even decreased. As a result, blood pressure remained un changed or even increased. In contrast, during combined ultrafiltratio n-haemodialysis at a dialysate temperature of 37.5 degrees C the incre ase in forearm vascular resistance was only small and insignificant, w hile venous tone decreased significantly. Heart rate tended to increas e. Combined ultrafiltration-haemodialysis at a dialysate temperature o f 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 wel l maintained. Conclusions. We conclude that differences in cardiovascu lar reactivity between isolated ultrafiltration and combined ultrafilt ration-haemodialysis are only partially explained by differences in th e extracorporeal blood temperature. In addition, especially reactivity is improved by lowering the dialysate temperature.