The estimation of representative blood pressure (BP) levels is difficult in haemodialysis (HD) patients as it is not known whether pre- or postdialytic blood pressure are predictive for the average interdialytic BP. Furthermore, the day-night BP rhythm can be disturbed in HD patients. Therefore, in this study, BP was measured during the interdialytic period using non-invasive ambulatory BP measurements in four hypotensive, six normotensive, and 12 hypertensive HD patients. It was assessed whether pre- or postdialytic BP was representative for the average interdialytic BP. Furthermore, the nocturnal BP reduction was compared between HD patients, seven normotensive controls and eight treated subjects with essential hypertension. Postdialytic BP was superior to predialytic BP in predicting the average BP during the interdialytic period. BP did not differ significantly between day 1 and day 2 of the interdialytic period but increased rapidly in the hours before dialysis. Weight gain (corrected for actual body-weight) did not correlate significantly with the increment in systolic BP (r = 0.21; P = 0.2) or diastolic BP (r = -0.02; P = 0.5) during the interdialytic period. The nocturnal decline in systolic BP was significantly attenuated (P less than 0.001) in hypertensive HD patients compared with normotensive controls. The nocturnal reduction in diastolic BP was significantly less in hypotensive (P less than 0.001) and normotensive (P less than 0.001) HD patients compared with normotensive controls and in hypertensive HD patients compared with normotensive (P less than 0.001) and hypertensive (P less than 0.001) controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Abstract.Differences in vascular reactivity between isolated ultrafiltration (i-UF) and hemodialysis (UF + HD) have been attributed to various factors, including differences in core temperature (CT) and energy transfer (ET). However, the relative importance of these thermal factors is not known. The aim of this study was to elucidate to what extent differences in ET are responsible for the divergent vascular response between i-UF and UF + HD. During four different dialysis treatments in 15 patients, four measurements were performed that consisted of 1 h of i-UF, UF + HD at a dialysate temperature (Td) of 37.5°C (UF + HD37.5), UF + HD atTd35.5°C (UF + HD35.5), and UF + HD with a similar ET as during i-UF(UF + HDET-set). The UF rate in all sessions was 1 L/h. CT (°C) decreased significantly during i-UF and UF + HDET-set(P< 0.05), increased significantly during UF + HD37.5(P< 0.05), and remained unchanged during UF + HD35.5(NS). Forearm vascular reactivity increased significantly during i-UF, UF + HDET-set, and UF + HD35.5(P< 0.05), but not during UF + HD37.5(NS). Venous tone increased significantly during i-UF, UF + HD35.5, and UF + HDET-set(P< 0.05), and decreased significantly during UF + HD37.5(P< 0.05). When i-UF and UF + HD are matched for ET, all differences in vascular response disappear, showing that differences in ET are the single most important factor for the observed difference in vascular response between i-UF and UF + HD. In contrast to UF + HD37.5, vascular reactivity was improved when the increase in CT was prevented during UF + HD35.5and appeared to increase more when CT was lowered. Preventing the increase in CT during UF + HD appears to be mandatory for optimization of hemodynamic stability during dialysis.